VNET (VNET) 20-F 28 Apr 21 2020 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2020shares
Document and Entity Information
Document Type	20-F
Document Registration Statement	false
Document Annual Report	true
Document Transition Report	false
Document Shell Company Report	false
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity File Number	001-35126
Entity Registrant Name	21VIANET GROUP, INC.
Entity Central Index Key	0001508475
Current Fiscal Year End Date	--12-31
Entity Incorporation, State or Country Code	E9
Entity Address, Address Line One	Guanjie Building Southeast 1st Floor
Entity Address, Address Line Two	10# Jiuxianqiao East Road
Entity Address, Address Line Three	Chaoyang District
Entity Address, City or Town	Beijing
Entity Address, Postal Zip Code	100016
Entity Address, Country	CN
Title of 12(b) Security	American depositary shares, each representing six Class A ordinary shares, par value US$0.00001 per share
Trading Symbol	VNET
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Document Accounting Standard	U.S. GAAP
Entity Shell Company	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Business Contact
Document and Entity Information
Entity Address, Address Line One	Guanjie Building, Southeast 1st Floor
Entity Address, Address Line Two	10# Jiuxianqiao East Road
Entity Address, Address Line Three	Chaoyang District
Entity Address, City or Town	Beijing
Entity Address, Postal Zip Code	100016
Entity Address, Country	CN
Contact Personnel Name	Ms. Sharon Xiao Liu
City Area Code	86
Local Phone Number	10 8456-2121
Class A Ordinary Shares
Document and Entity Information
Entity Common Stock, Shares Outstanding	672,024,600
Class B Ordinary Shares
Document and Entity Information
Entity Common Stock, Shares Outstanding	145,875,113
Class C Ordinary Shares
Document and Entity Information
Entity Common Stock, Shares Outstanding	60,000

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Current assets:
Cash and cash equivalents	¥ 2,710,349	$ 415,379	¥ 1,808,483
Restricted cash	270,450	41,448	478,873
Accounts and notes receivable (net of allowance for doubtful debt of RMB67,828 and RMB68,921 (US$10,563) as of December 31, 2019 and 2020, respectively)	847,233	129,844	657,158
Short-term investments	285,872	43,812	363,856
Prepaid expenses and other current assets	1,866,184	286,005	1,618,149
Amounts due from related parties	75,519	11,574	301,665
Total current assets	6,055,607	928,062	5,228,184
Non-current assets:
Property and equipment, net	8,106,425	1,242,364	5,443,565
Intangible assets, net	658,195	100,873	410,595
Land use rights, net	255,373	39,138	233,154
Operating lease right-of-use assets, net	1,325,526	203,146	1,221,616
Goodwill	994,993	152,489	989,530
Restricted cash	135,638	20,787	69,821
Deferred tax assets, net	185,481	28,426	209,366
Long-term investments, net	135,517	20,769	169,653
Amounts due from related parties	20,562	3,151	20,654
Other non-current assets	1,500,438	229,952	277,568
Total non-current assets	13,318,148	2,041,095	9,045,522
Total assets	19,373,755	2,969,157	14,273,706
Current liabilities:
Short-term bank borrowings (including short-term bank borrowings of the Consolidated VIEs without recourse to the primary beneficiaries of RMB232,323 and RMB 34,000 (US$ 5,211) as of December 31, 2019 and 2020, respectively)	34,000	5,211	234,500
Accounts and notes payable (including accounts and notes payable of the Consolidated VIEs without recourse to the primary beneficiaries of RMB211,710 and RMB182,669 (US$27,995) as of December 31, 2019 and 2020, respectively)	289,387	44,350	303,128
Accrued expenses and other payables (including accrued expenses and other payables of the Consolidated VIEs without recourse to the primary beneficiaries of RMB622,160 and RMB 981,962 (US$ 150,492) as of December 31, 2019 and 2020, respectively)	1,631,563	250,048	978,935
Advances from customers (including advances from customers of the Consolidated VIEs without recourse to the primary beneficiaries of RMB1,068,692 and RMB1,041,594 (US$159,631) as of December 31, 2019 and 2020, respectively)	1,041,594	159,631	1,068,692
Deferred revenue (including deferred revenue of the Consolidated VIEs without recourse to the primary beneficiaries of RMB52,088 and RMB 58,065 (US$ 8,899) as of December 31, 2019 and 2020, respectively)	63,245	9,693	57,625
Income taxes payable (including income taxes payable of the Consolidated VIEs without recourse to the primary beneficiaries of RMB8,175 and RMB12,743 (US$1,953) as of December 31, 2019 and 2020, respectively)	29,028	4,449	48,032
Amounts due to related parties (including amounts due to related parties of the Consolidated VIEs without recourse to the primary beneficiaries of RMB56,977 and RMB 50,193 (US$ 7,692) as of December 31, 2019 and 2020, respectively)	51,007	7,817	166,935
Current portion of long-term borrowings (including current portion of long-term borrowings of the Consolidated VIEs without recourse to the primary beneficiaries of RMB32,500 and RMB165,328 (US$ 25,338) as of December 31, 2019 and 2020, respectively)	180,328	27,636	32,500
Current portion of finance lease liabilities (including current portion of finance lease liabilities of the Consolidated VIEs without recourse to the primary beneficiaries of RMB220,363 and RMB362,760 (US$55,595) as of December 31, 2019 and 2020, respectively)	403,843	61,892	227,115
Deferred government grants (including deferred government grants of the Consolidated VIEs without recourse to the primary beneficiaries of RMB2,595 and RMB 2,074 (US$ 318) as of December 31, 2019 and 2020, respectively)	2,074	318	2,595
Current portion of bonds payable	1,943,619	297,873	911,147
Current portion of operating lease liabilities (including current portion of operating lease liabilities of the Consolidated VIEs without recourse to the primary beneficiaries of RMB410,422 and RMB 427,114 (US$ 65,458) as of December 31, 2019 and 2020, respectively)	452,272	69,314	437,817
Total current liabilities	6,121,960	938,232	4,469,021
Non-current liabilities:
Long-term borrowings (including long-term borrowings of the Consolidated VIEs without recourse to the primary beneficiaries of RMB79,500 and RMB570,135 (US$87,377) as of December 31, 2019 and 2020, respectively)	886,996	135,938	79,500
Bonds payable			2,060,708
Convertible promissory notes	3,014,057	461,924
Non-current portion of finance lease liabilities (including non-current portion of finance lease liabilities of the Consolidated VIEs without recourse to the primary beneficiaries of RMB549,669 and RMB299,399 (US$45,885) as of December 31, 2019 and 2020, respectively)	688,128	105,460	896,927
Unrecognized tax benefits (including unrecognized tax benefits of the Consolidated VIEs without recourse to the primary beneficiaries of RMB1,991 and RMB68,317 (US$10,470) as of December 31, 2019 and 2020, respectively)	68,696	10,528	2,443
Deferred tax liabilities (including deferred tax liabilities of the Consolidated VIEs without recourse to the primary beneficiaries of RMB82,725 and RMB155,281 (US$23,798) as of December 31, 2019 and 2020, respectively)	299,093	45,838	202,572
Deferred government grants (including deferred government grants of the Consolidated VIEs without recourse to the primary beneficiaries of RMB5,906 and RMB4,100 (US$628) as of December 31, 2019 and 2020, respectively)	4,100	628	5,906
Amounts due to related parties (including amounts due to related parties of the Consolidated VIEs without resource to the primary beneficiaries of RMB745,899 and RMB 747,746 (US$ 114,597) as of December 31, 2019 and 2020, respectively)	747,746	114,597	745,899
Non-current portion of operating lease liabilities (including non-current portion of operating lease liabilities of the Consolidated VIEs without resource to the primary beneficiaries of RMB529,546 and RMB 497,268 (US$ 76,210) as of December 31, 2019 and 2020, respectively)	645,499	98,927	579,102
Total non-current liabilities	6,354,315	973,840	4,573,057
Total liabilities	12,476,275	1,912,072	9,042,078
Commitments and contingencies
Shareholders' equity:
Series A perpetual convertible preferred shares (par value of US$0.00001 per share; nil and 150,000 shares issued and outstanding as of December 31, 2019 and 2020, respectively)	1,047,468	160,531
Additional paid-in capital	13,083,119	2,005,076	9,202,567
Accumulated other comprehensive loss (income)	(55,535)	(8,511)	77,904
Statutory reserves	74,462	11,412	60,469
Accumulated deficit	(7,235,113)	(1,108,830)	(4,038,390)
Treasury stock	(349,523)	(53,567)	(349,523)
Total shareholders' equity	6,564,934	1,006,120	4,953,073
Noncontrolling interest	332,546	50,965	278,555
Total shareholders' equity	6,897,480	1,057,085	5,231,628
Total liabilities and shareholders' equity	19,373,755	2,969,157	14,273,706
Class A Ordinary Shares
Shareholders' equity:
Ordinary shares	44	7	34
Class B Ordinary Shares
Shareholders' equity:
Ordinary shares	12	2	¥ 12
Series A Perpetual Convertible Preferred Shares
Shareholders' equity:
Ordinary shares	¥ 1,047,468	$ 160,531

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019CNY (¥)shares	Dec. 31, 2019USD ($)$ / sharesshares
Accounts and notes receivable, allowance for doubtful accounts	¥ 68,921	$ 10,563	¥ 67,828	$ 10,395
Short-term bank and other borrowings of the Consolidated VIEs without recourse to the primary beneficiaries	34,000	5,211	234,500
Accounts and notes payable of the Consolidated VIEs without recourse to the primary beneficiaries	289,387	44,350	303,128
Accrued expenses and other payables of the Consolidated VIEs without recourse to the primary beneficiaries	1,631,563	250,048	978,935
Advance from customers of the Consolidated VIEs without recourse to the primary beneficiaries	1,041,594	159,631	1,068,692
Deferred revenue of the Consolidated VIEs without recourse to the primary beneficiaries	63,245	9,693	57,625
Income tax payables of the Consolidated VIEs without recourse to the primary beneficiaries	29,028	4,449	48,032
Amounts due to related parties of the consolidated VIEs without resource to the primary beneficiaries	51,007	7,817	166,935
Long-term bank borrowings, current portion	68,500	10,498	32,500
Current portion of finance lease liabilities of the Consolidated VIEs without recourse to the primary beneficiaries.	403,843	61,892	227,115
Deferred government grants of the Consolidated VIEs without recourse to the primary beneficiaries	2,074	318	2,595
Current portion of operating lease liabilities	452,272	69,314	437,817
Long-term bank borrowings of the Consolidated VIEs without recourse to the primary beneficiaries	605,119	92,738	79,500
Long-term bank borrowings of the Consolidated VIEs without recourse to the primary beneficiaries	886,996	135,938	79,500
Non-current portion of finance lease liabilities	688,128	105,460	896,927
Unrecognized tax benefits of the Consolidated VIEs without recourse to the primary beneficiaries	68,696	10,528	2,443
Deferred tax liabilities of the Consolidated VIEs without recourse to the primary beneficiaries	299,093	45,838	202,572
Deferred government grants of the Consolidated VIEs without recourse to the primary beneficiaries	4,100	628	5,906
Amounts due to related parties related parties of the consolidated VIEs without resource to the primary beneficiaries	747,746	114,597	745,899
Non-current portion of operating lease liabilities	¥ 645,499	$ 98,927	¥ 579,102
Series A perpetual convertible preferred shares, par value | $ / shares		$ 0.00001
Series A perpetual convertible preferred shares, shares issued	150,000	150,000	0	0
Series A perpetual convertible preferred shares, shares outstanding	150,000	150,000	0	0
Variable Interest Entity, Primary Beneficiary
Short-term bank and other borrowings of the Consolidated VIEs without recourse to the primary beneficiaries	¥ 34,000	$ 5,211	¥ 232,323
Accounts and notes payable of the Consolidated VIEs without recourse to the primary beneficiaries	182,669	27,995	211,710
Accrued expenses and other payables of the Consolidated VIEs without recourse to the primary beneficiaries	981,961	150,492	622,160
Advance from customers of the Consolidated VIEs without recourse to the primary beneficiaries	1,041,594	159,631	1,068,692
Deferred revenue of the Consolidated VIEs without recourse to the primary beneficiaries	58,066	8,899	52,088
Income tax payables of the Consolidated VIEs without recourse to the primary beneficiaries	12,743	1,953	8,175
Amounts due to related parties of the consolidated VIEs without resource to the primary beneficiaries	50,193	7,692	56,977
Long-term bank borrowings, current portion	165,328	25,338	32,500
Current portion of finance lease liabilities of the Consolidated VIEs without recourse to the primary beneficiaries.	362,760	55,595	220,363
Deferred government grants of the Consolidated VIEs without recourse to the primary beneficiaries	2,074	318	2,595
Current portion of operating lease liabilities	427,114	65,458	410,422
Long-term bank borrowings of the Consolidated VIEs without recourse to the primary beneficiaries	570,135	87,377	79,500
Non-current portion of finance lease liabilities	299,399	45,885	549,669
Unrecognized tax benefits of the Consolidated VIEs without recourse to the primary beneficiaries	68,317	10,470	1,991
Deferred tax liabilities of the Consolidated VIEs without recourse to the primary beneficiaries	155,281	23,798	82,725
Deferred government grants of the Consolidated VIEs without recourse to the primary beneficiaries	4,100	628	5,906
Amounts due to related parties related parties of the consolidated VIEs without resource to the primary beneficiaries	747,746	114,597	745,899
Non-current portion of operating lease liabilities	¥ 497,268	$ 76,210	¥ 529,546
Class A Ordinary Shares
Ordinary shares, par value (in dollars per share) | $ / shares		$ 0.00001
Ordinary shares, shares authorized (in shares)	1,199,790,000	1,199,790,000	1,200,000,000	1,200,000,000
Ordinary shares, shares issued (in shares)	672,024,600	672,024,600	505,253,850	505,253,850
Ordinary shares, shares outstanding (in shares)	672,024,600	672,024,600	505,253,850	505,253,850
Class B Ordinary Shares
Ordinary shares, par value (in dollars per share) | $ / shares		$ 0.00001		$ 0.00001
Ordinary shares, shares authorized (in shares)	300,000,000	300,000,000	300,000,000	300,000,000
Ordinary shares, shares issued (in shares)	145,875,113	145,875,113	174,649,638	174,649,638
Ordinary shares, shares outstanding (in shares)	145,875,113	145,875,113	174,649,638	174,649,638
Class C Ordinary Shares
Ordinary shares, par value (in dollars per share) | $ / shares		$ 0.00001
Ordinary shares, shares authorized (in shares)	60,000	60,000	60,000	60,000
Ordinary shares, shares issued (in shares)	60,000	60,000	60,000	60,000
Ordinary shares, shares outstanding (in shares)	60,000	60,000	60,000	60,000
Series A Perpetual Convertible Preferred Shares
Ordinary shares, shares issued (in shares)	150,000	150,000
Ordinary shares, shares outstanding (in shares)	150,000	150,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)¥ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019CNY (¥)¥ / sharesshares	Dec. 31, 2018CNY (¥)¥ / sharesshares
Net revenues
Hosting and related services	¥ 4,829,019	$ 740,080	¥ 3,788,967	¥ 3,401,037
Hosting and related services	(3,753,008)	(575,174)	(2,849,518)	(2,456,166)
Gross profit	1,076,011	164,906	939,449	944,871
Operating income (expenses)
Operating income	7,619	1,168	6,862	5,027
Sales and marketing expenses	(235,012)	(36,017)	(206,309)	(172,176)
Research and development expenses	(112,891)	(17,301)	(88,792)	(92,109)
General and administrative expenses	(535,111)	(82,009)	(415,277)	(462,637)
Reversal (allowance) for doubtful debt	(2,393)	(367)	(1,557)	598
Impairment of receivables from equity investees			(52,142)
Changes in the fair value of contingent purchase consideration payables				13,905
Impairment of long-lived assets	(81,619)	(12,509)
Total operating expenses	(959,407)	(147,035)	(757,215)	(707,392)
Operating profit	116,604	17,871	182,234	237,479
Interest income	31,711	4,860	54,607	45,186
Interest expense	(380,609)	(58,331)	(345,955)	(236,066)
Gain on deconsolidation of subsidiaries				4,843
Loss on debt extinguishment			(18,895)
Other income	16,539	2,535	36,380	58,033
Other expenses	(36,912)	(5,657)	(5,632)	(4,103)
Changes in the fair value of convertible promissory notes	(2,544,220)	(389,919)
Impairment of long-term investment	(13,030)	(1,997)
Foreign exchange (loss) gain, net	228,125	34,962	(27,995)	(81,055)
Income (loss) before income taxes and (loss) gain from equity method investments	(2,581,792)	(395,676)	(125,256)	24,317
Income tax expenses	(109,336)	(16,756)	(5,437)	(24,411)
(Loss) gain from equity method investments	10,869	1,666	(50,553)	(186,642)
Net loss	(2,680,259)	(410,766)	(181,246)	(186,736)
Net income attributable to noncontrolling interest	(29,088)	(4,458)	(1,046)	(18,329)
Net loss attributable to the 21Vianet Group, Inc.	¥ (2,709,347)	$ (415,224)	¥ (182,292)	¥ (205,065)
Loss per share:
Basic (in per share) | (per share)	¥ (4.47)	$ (0.69)	¥ (0.27)	¥ (0.30)
Diluted (in per share) | (per share)	¥ (4.47)	$ (0.69)	¥ (0.27)	¥ (0.30)
Shares used in loss per share computation:
Weighted average number of shares outstanding - basic (in shares) | shares	716,888,919	716,888,919	668,833,756	674,732,130
Weighted-average number of shares outstanding-diluted (in shares) | shares	716,888,919	716,888,919	668,833,756	674,732,130

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Net loss	¥ (2,680,259)	$ (410,766)	¥ (181,246)	¥ (186,736)
Other comprehensive income (loss), net of tax of nil
Foreign currency translation adjustments, net of tax of nil	(133,439)	(20,450)	(8,075)	88,652
Other comprehensive income (loss), net of tax of nil	(133,439)	(20,450)	(8,075)	88,652
Comprehensive loss	(2,813,698)	(431,216)	(189,321)	(98,084)
Comprehensive income attributable to noncontrolling interest	(29,088)	(4,458)	(1,046)	(18,329)
Comprehensive loss attributable to 21Vianet Group, Inc.	¥ (2,842,786)	$ (435,674)	¥ (190,367)	¥ (116,413)

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Parenthetical) - CNY (¥) ¥ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Foreign currency translation adjustments, tax	¥ 0	¥ 0	¥ 0
Other comprehensive income, tax	¥ 0	¥ 0	¥ 0

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	¥ (2,680,259,000)	$ (410,766,000)	¥ (181,246,000)	¥ (186,736,000)
Adjustments to reconcile net loss to net cash generated from operating activities:
Foreign exchange loss (gain), net	(228,125,000)	(34,962,000)	27,995,000	81,055,000
Changes in the fair value of contingent purchase consideration payables				(13,905,000)
Gain from settlement of contingent purchase consideration				(500,000)
Depreciation and amortization	988,983,000	151,568,000	772,205,000	634,606,000
(Gain) loss on disposal of property and equipment and intangible assets	6,032,000	922,000	271,000	(7,981,000)
(Reversal) allowance for doubtful debt	2,393,000	367,000	1,557,000	(598,000)
Share-based compensation expense	136,804,000	20,966,000	43,916,000	59,538,000
Impairment of receivables from equity investees			52,142,000
Deferred income tax benefits	(22,508,000)	(3,450,000)	(64,887,000)	(19,776,000)
Loss (gain) from equity method investments	(10,869,000)	(1,666,000)	50,553,000	186,642,000
Distribution received from an equity method investment	17,723,000	2,716,000	20,200,000
Gain from disposal of equity investments without readily determinable fair value	(257,000)	(39,000)	(5,536,000)	(20,496,000)
Gain from disposal of equity method investment			(17,853,000)	(16,509,000)
Dividend income of equity investments without readily determinable fair values				(406,000)
Gain from disposal of subsidiaries				(4,843,000)
Impairment of long-lived assets	81,619,000	12,509,000
Impairment of a long-term investment	13,030,000	1,997,000
Loss on debt extinguishment			18,895,000
Lease expenses	375,112,000	57,488,000	205,787,000
Changes in the fair value of convertible promissory notes	2,544,220,000	389,919,000
Changes in operating assets and liabilities, net of effects of acquisitions and disposals:
Accounts and notes receivable	(171,608,000)	(26,300,000)	(156,134,000)	(68,809,000)
Prepaid expenses and other current assets	(117,110,000)	(17,946,000)	(328,224,000)	(262,445,000)
Amounts due from related parties	37,468,000	5,742,000	11,352,000	(38,047,000)
Accounts and notes payables	(13,741,000)	(2,106,000)	9,185,000	41,380,000
Unrecognized tax benefits	66,253,000	10,154,000	(4,234,000)	(9,834,000)
Accrued expenses and other payables	91,123,000	13,966,000	77,275,000	77,744,000
Deferred revenue	5,620,000	861,000	(129,000)	2,001,000
Advances from customers	(27,098,000)	(4,153,000)	398,655,000	266,793,000
Income taxes payable	(19,004,000)	(2,912,000)	34,917,000	(198,000)
Deferred government grants			500,000	(6,643,000)
Amounts due to related parties	(5,605,000)	(859,000)	6,044,000	12,933,000
Operating lease liabilities	(355,953,000)	(54,552,000)	(170,284,000)
Net cash generated from operating activities	714,243,000	109,464,000	802,922,000	704,966,000
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(2,473,332,000)	(379,055,000)	(1,248,834,000)	(435,220,000)
Purchases of intangible assets	(30,091,000)	(4,612,000)	(26,515,000)	(17,874,000)
Purchases of land use rights			(24,460,000)
Proceeds from disposal of property and equipment	1,777,000	272,000	2,484,000	15,429,000
Proceeds from disposal of land use right	9,397,000	1,440,000
Proceed from disposal of subsidiaries, net	5,802,000	889,000		3,389,000
Payments for short-term investments	(328,182,000)	(50,296,000)	(436,737,000)	(98,905,000)
Payment of loan to a third party	(12,562,000)	(1,925,000)		(20,000,000)
Payment of loans to related parties	(62,531,000)	(9,583,000)	(66,704,000)
Receipt of loans to third parties	30,000,000	4,598,000		20,413,000
Proceeds received from maturity of short-term investments	397,575,000	60,931,000	312,198,000	417,643,000
Proceeds from disposal of long-term investments	1,923,000	295,000	18,955,000	75,653,000
Proceeds from dividend income of equity investments without readily determinable fair values				406,000
Payments for long-term investments			(9,330,000)	(252,780,000)
Prepayments and deposits for acquiring data center	(1,302,601,000)	(199,633,000)	(82,536,000)	(13,000,000)
Collection of deposit for acquiring data center	106,436,000	16,312,000	30,000,000
Payments for acquisitions, net of cash acquired	(369,924,000)	(56,693,000)	(148,067,000)
Cash receipt from related parties due to restructuring	140,738,000	21,569,000	67,563,000
Payment for other investment activities	(3,599,000)	(552,000)
Net cash used in investing activities	(3,889,174,000)	(596,043,000)	(1,611,983,000)	(304,846,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from loan from a related party				44,038,000
Repayment of loan from a related party			(47,893,000)
Proceeds from exercise of stock options	3,029,000	464,000	429,000	435,000
Proceeds from issuance of ordinary shares	2,680,421,000	410,792,000	572,000
Proceeds from Series A perpetual convertible preferred shares	1,058,325,000	162,195,000
Payment of issuance cost of Series A perpetual convertible preferred shares	(9,374,000)	(1,437,000)
Proceeds from long-term bank borrowings	594,619,000	91,129,000
Proceeds from short-term bank borrowings	34,000,000	5,211,000	234,500,000	69,999,000
Proceeds from other long-term borrowings	374,448,000	57,387,000	110,000,000
Repayment of long-term bank borrowings	(33,000,000)	(5,057,000)	(85,110,000)	(70,643,000)
Repayment of short-term bank borrowings	(234,500,000)	(35,939,000)	(50,000,000)	(69,999,000)
Repayment and deposits for other long-term borrowings	(125,825,000)	(19,284,000)	(19,399,000)	(48,401,000)
Payments for purchase of property and equipment through finance leases	(376,232,000)	(57,660,000)	(333,614,000)	(279,886,000)
Repayment of loan from third parties	(169,325,000)	(25,950,000)	(67,659,000)
Contribution from noncontrolling interest in subsidiaries	24,903,000	3,817,000	8,532,000	196,281,000
Prepayment for future share repurchase plan			(9,778,000)
Refund of prepayment for share repurchase plan				42,710,000
Payments for share repurchase	(130,472,000)	(19,996,000)	(11,840,000)
Proceeds from discounted notes				95,565,000
Repayment of notes payable			(95,565,000)
Net cash (used in) generated from financing activities	4,163,255,000	638,046,000	461,557,000	(19,901,000)
Effect of foreign exchange rate changes on cash and cash equivalents and restricted cash	(229,064,000)	(35,106,000)	43,660,000	85,333,000
Net increase (decrease) in cash and cash equivalents and restricted cash	759,260,000	116,361,000	(303,844,000)	465,552,000
Cash and cash equivalents and restricted cash at beginning of the year	2,357,177,000	361,253,000	2,661,021,000	2,195,469,000
Cash and cash equivalents and restricted cash at end of the year	3,116,437,000	477,614,000	2,357,177,000	2,661,021,000
Reconciliation of cash and cash equivalents and restricted cash to the consolidated balance sheets
Cash and cash equivalents	2,710,349,000	415,379,000	1,808,483,000	2,358,556,000
Restricted cash-current	270,450,000	41,448,000	478,873,000	265,214,000
Restricted cash-non-current	135,638,000	20,787,000	69,821,000	37,251,000
Cash and cash equivalents and restricted cash at end of the year	3,116,437,000	477,614,000	2,357,177,000	2,661,021,000
Supplemental disclosures of cash flow information:
Income taxes paid	(102,330,000)	(15,683,000)	(41,684,000)	(57,407,000)
Interest paid	(284,270,000)	(43,566,000)	(215,889,000)	(160,984,000)
Interest received	37,817,000	5,796,000	59,054,000	50,793,000
Supplemental disclosures of non-cash activities:
Right-of-use assets obtained in exchange for new operating lease liabilities	479,022,000	73,413,000	618,126,000
Purchase of property and equipment through finance leases	217,190,000	33,286,000	357,573,000	884,871,000
Purchase of property and equipment included in accrued expenses and other payables	591,187,000	90,603,000	344,248,000	21,918,000
Purchase of intangible assets included in accrued expenses and other payables	2,862,000	439,000	(1,642,000)	870,000
Contingent consideration related to the acquisitions included in amounts due to related parties and accrued expenses and other payables				¥ 36,734,000
Bonds 7% Due 2020
CASH FLOWS FROM FINANCING ACTIVITIES
Repurchase and repayment	(915,543,000)	(140,313,000)	(1,148,092,000)
2021 Notes
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance cost			2,012,084,000
Payment of issuance cost			¥ (35,610,000)
Convertible Notes Payable [Member]
Adjustments to reconcile net loss to net cash generated from operating activities:
Changes in the fair value of convertible promissory notes	2,544,220	389,919
CASH FLOWS FROM FINANCING ACTIVITIES
Payment of Conversion Cost	(2,763,000)	(423,000)
Proceeds from issuance cost	1,409,385,000	215,998,000
Payment of issuance cost	¥ (18,841,000)	$ (2,888,000)

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY ¥ in Thousands	Ordinary sharesCNY (¥)shares	Ordinary sharesUSD ($)shares	Treasury stockCNY (¥)	Treasury stockUSD ($)	Additional paid-in capitalCNY (¥)	Additional paid-in capitalUSD ($)	Series A Perpetual Convertible Preferred ShareholdersCNY (¥)	Series A Perpetual Convertible Preferred ShareholdersUSD ($)	Accumulated other comprehensive (loss) incomeCNY (¥)	Accumulated other comprehensive (loss) incomeUSD ($)	Statutory reservesCNY (¥)	Statutory reservesUSD ($)	Accumulated deficitCumulative Effect, Period of Adoption, Adjustment [Member]CNY (¥)	Accumulated deficitCNY (¥)	Accumulated deficitUSD ($)	Total 21Vianet Group, Inc. shareholders' equityCumulative Effect, Period of Adoption, Adjustment [Member]CNY (¥)	Total 21Vianet Group, Inc. shareholders' equityCNY (¥)	Total 21Vianet Group, Inc. shareholders' equityUSD ($)	Non-controlling interestCNY (¥)	Non-controlling interestUSD ($)	Cumulative Effect, Period of Adoption, Adjustment [Member]CNY (¥)	CNY (¥)shares	USD ($)shares
Cumulative adjustment for changes in accounting policy	¥ 46		¥ (337,683)		¥ 8,980,407				¥ (2,673)		¥ 38,736			¥ (3,629,300)			¥ 5,049,533		¥ 151,471			¥ 5,201,004
Beginning Balance (in shares) at Dec. 31, 2017 | shares	671,285,766	671,285,766
Beginning balance at Dec. 31, 2017	¥ 46		(337,683)		8,980,407				(2,673)		38,736			(3,629,300)			5,049,533		151,471			5,201,004
Consolidated net loss														(205,065)			(205,065)		18,329			(186,736)
Cumulative adjustment for changes in accounting policy	¥ 46		(337,683)		9,141,494				85,979		42,403			(3,838,032)			5,094,207		268,977			5,363,184
Foreign exchange difference					477				88,652								89,129					89,129
Issuance of new shares for share option exercised and restricted share units vested (in shares) | shares	3,070,500	3,070,500
Share-based compensation					67,009												67,009					67,009
Appropriation of statutory reserves											3,667			(3,667)
Disposal of 49% interest in a subsidiary					93,166												93,166		103,115			¥ 196,281
Shares issued to depository bank (in shares) | shares																						0	0
Disposal of subsidiaries																			(3,938)			¥ (3,938)
Share repurchase (in shares) | shares																						0	0
Share options exercised					435												435					¥ 435
Share options exercised (in shares) | shares	219,972	219,972
Restricted share units vested (shares) | shares	5,115,558	5,115,558
Settlement of share options and restricted share units with shares held by depository bank (in shares) | shares	(5,335,530)	(5,335,530)
Ending Balance (in shares) at Dec. 31, 2018 | shares	674,356,266	674,356,266
Ending balance at Dec. 31, 2018	¥ 46		(337,683)		9,141,494				85,979		42,403			(3,838,032)			5,094,207		268,977			5,363,184
Cumulative adjustment for changes in accounting policy	46		(337,683)		9,141,494				85,979		42,403			(3,838,032)			5,094,207		268,977			5,363,184
Consolidated net loss														(182,292)			(182,292)		1,046			(181,246)
Contribution by noncontrolling interest																			8,532			8,532
Cumulative adjustment for changes in accounting policy	¥ 46		(349,523)		9,202,567				77,904		60,469			(4,038,390)			4,953,073		278,555			5,363,184
Foreign exchange difference					24				(8,075)								(8,051)					(8,051)
Issuance of new shares					572												572					572
Number of shares issued | shares	60,000	60,000
Issuance of new shares for share option exercised and restricted share units vested (in shares) | shares	304,200	304,200
Share-based compensation					60,048												60,048					¥ 60,048
Appropriation of statutory reserves											18,066			(18,066)
Shares issued to depository bank (in shares) | shares	6,700,002	6,700,002																				6,700,002	6,700,002
Share repurchase			(11,840)														(11,840)					¥ (11,840)
Share repurchase (in shares) | shares	(1,456,980)	(1,456,980)																				(242,830)	(242,830)
Share options exercised					429												429					¥ 429
Share options exercised (in shares) | shares	33,869	33,869
Restricted share units vested (shares) | shares	5,136,306	5,136,306
Settlement of share options and restricted share units with shares held by depository bank (in shares) | shares	(5,170,175)	(5,170,175)
Ending Balance (in shares) at Dec. 31, 2019 | shares	679,963,488	679,963,488
Ending balance at Dec. 31, 2019	¥ 46		(349,523)		9,202,567				77,904		60,469			(4,038,390)			4,953,073		278,555			5,231,628
Cumulative adjustment for changes in accounting policy	46		(349,523)		9,202,567				77,904		60,469			(4,038,390)			4,953,073		278,555			5,231,628
Consolidated net loss														(2,709,347)			(2,709,347)		29,088			(2,680,259)
Contribution by noncontrolling interest																			24,903			24,903
Cumulative adjustment for changes in accounting policy	56	$ 9,000	(349,523)	$ (53,567,000)	13,083,119	$ 2,005,076,000	¥ 1,047,468	$ 160,531,000	(55,535)	$ (8,511,000)	74,462	$ 11,412,000	¥ (2,740)	(7,235,113)	$ (1,108,830,000)	¥ (2,740)	6,564,934	$ 1,006,120,000	332,546	$ 50,965,000	¥ (2,740)	6,897,480	$ 1,057,085,000
Foreign exchange difference									(133,439)								(133,439)					(133,439)
Issuance of new shares	¥ 8				2,680,283												2,680,291					2,680,291
Number of shares issued | shares	118,754,028	118,754,028
Issuance of perpetual convertible preferred shares							1,047,468										1,047,468					1,047,468
Deemed distribution to perpetual convertible preferred shares					470,643									(470,643)
Cancellation of shares issued in prior years (in shares) | shares	(104,304)	(104,304)
Conversion of convertible promissory notes	¥ 2				717,606												717,608					717,608
Conversion of convertible promissory notes (in shares) | shares	23,710,140	23,710,140
Share-based compensation					139,641												139,641					¥ 139,641
Appropriation of statutory reserves											13,993			(13,993)
Shares issued to depository bank (in shares) | shares																						0	0
Share repurchase | $		$ (4,363,639)
Share repurchase (in shares) | shares																						0	0
Share options exercised	¥ 0		0		3,029		0		0		0			0			3,029		0			¥ 3,029
Share options exercised (in shares) | shares	459,168	459,168
Restricted share units vested	¥ 0		0		0		0		0		0			0			0		0			0
Restricted share units vested (shares) | shares	2,603,430	2,603,430
Settlement of share options and restricted share units with shares held by depository bank	¥ 0		0		0		0		0		0			0			0		0			0
Settlement of share options and restricted share units with shares held by depository bank (in shares) | shares	(3,062,598)	(3,062,598)
Ending Balance (in shares) at Dec. 31, 2020 | shares	817,959,713	817,959,713
Ending balance at Dec. 31, 2020	¥ 56	$ 9,000	(349,523)	(53,567,000)	13,083,119	2,005,076,000	1,047,468	160,531,000	(55,535)	(8,511,000)	74,462	11,412,000	(2,740)	(7,235,113)	(1,108,830,000)	(2,740)	6,564,934	1,006,120,000	332,546	50,965,000	(2,740)	6,897,480	$ 1,057,085,000
Cumulative adjustment for changes in accounting policy	¥ 56	$ 9,000	¥ (349,523)	$ (53,567,000)	¥ 13,083,119	$ 2,005,076,000	¥ 1,047,468	$ 160,531,000	¥ (55,535)	$ (8,511,000)	¥ 74,462	$ 11,412,000	¥ (2,740)	¥ (7,235,113)	$ (1,108,830,000)	¥ (2,740)	¥ 6,564,934	$ 1,006,120,000	¥ 332,546	$ 50,965,000	¥ (2,740)	¥ 6,897,480	$ 1,057,085,000

CONSOLIDATED STATEMENTS OF SH_2

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical)	Dec. 31, 2018	Mar. 31, 2017
Warburg Pincus
Noncontrolling interest, ownership percentage	49.00%	49.00%

ORGANIZATION

ORGANIZATION	12 Months Ended
	Dec. 31, 2020
ORGANIZATION
ORGANIZATION	1. ORGANIZATION 21Vianet Group, Inc. was incorporated under the laws of the Cayman Islands on October 16, 2009 and its principal activity is investment holding. The Company through its consolidated subsidiaries and variable interest entities (the “VIEs”) are principally engaged in the provision of hosting and related services. (a) As of December 31, 2020, the significant subsidiaries of the Company and consolidated variable interest entities are as follows: ​ Entity Date of Place of Percentage Principal activities ​ ​ ​ Direct ​ Subsidiaries: ​ ​ ​ ​ 21ViaNet Group Limited (“21Vianet HK”) ​ May 25, 2007 ​ Hong Kong ​ 100 % Investment holding 21Vianet Data Center Co., Ltd. (“21Vianet China”) (1) ​ June 12, 2000 ​ PRC ​ 100 % Provision of technical and consultation services and rental of long-lived assets 21Vianet (Foshan) Technology Co.,Ltd. (“FS Technology”) (1) ​ December 20, 2011 ​ PRC ​ 100 % Trading of network equipment, provision of technical and internet data center services 21Vianet Anhui Suzhou Technology Co.,Ltd. (“SZ Technology”) (1) ​ November 16, 2011 ​ PRC ​ 100 % Trading of network equipment 21Vianet Hangzhou Information Technology Co., Ltd. (“HZ Technology”) (1) ​ March 4, 2013 ​ PRC ​ 100 % Provision of internet data center services iJoy Holding Limited (“iJoy BVI”) ​ May 6, 2011 ​ British Virgin Islands ​ 100 % Investment holding 21Vianet Mobile Limited (“21V Mobile”) ​ April 30, 2013 ​ Hong Kong ​ 100 % Investment holding and provision of telecommunication services WiFire Group Inc. (“WiFire Group”) ​ March 7, 2014 ​ British Virgin Islands ​ 100 % Investment holding Joytone Infotech Co., Ltd. (“SZ Zhuoaiyi”) (1) ​ April 30, 2013 ​ PRC ​ 100 % Provision of technical and consultation services 21Vianet Ventures Limited (“Ventures”) ​ March 6, 2014 ​ Hong Kong ​ 100 % Investment holding Abitcool (China) Broadband Inc. (“aBitCool DG”) (1) ​ June 13, 2014 ​ PRC ​ 100 % Dormant company Diyixian.com Limited (“DYX”) ​ August 10, 2014 ​ Hong Kong ​ 100 % Provision of virtual private network services 21Vianet Zhuhai Financial Leasing Co., Ltd. (“Zhuhai Financial Leasing”) (1) ​ April 9, 2015 ​ PRC ​ 100 % Provision of finance leasing business services 21Vianet DRP Investment Holdings Limited (“DRP investment”) ​ January 10, 2017 ​ Hong Kong ​ 100 % Investment holding Shihua DC Investment Holdings Limited (“Shihua Investment”) ​ March 14, 2017 ​ Cayman Islands ​ 51 % Investment holding 21Vianet (Xi’an) Technology Co., Ltd. (“Xi’an Tech”) (1) ​ July 5, 2012 ​ PRC ​ 51 % Provision of technical and internet data center services Foshan Zhuoyi Intelligence Data Co., Ltd. (“FS Zhuoyi”) (1) ​ July 7, 2017 ​ PRC ​ 51 % Provision of internet data center services Beijing Hongyuan Network Technology Co., Ltd. (“BJ Hongyuan”) (1) ​ December 8, 2014 ​ PRC ​ 51 % Provision of internet data center services Dermot Holdings Limited (“Dermot BVI”) (3) ​ August 8, 2014 ​ British Virgin Islands ​ 100 % Investment holding Shihua DC Investment Holdings 2 Limited (“Shihua Holdings 2”) (4) ​ August 20, 2019 ​ Cayman Islands ​ 100 % Investment holding Shanghai Waigaoqiao Free Trade Zone Hongming Logistics Co., Ltd. (“Hongming Logistics”) (1) / (4) ​ August 20, 2019 ​ PRC ​ 100 % Provision of internet data center services Shanghai Edge Connect Technology Co., Ltd. (“SH Edge Connect”) (1) ​ November 3, 2020 ​ PRC ​ 100 % Provision of technical and internet data center services Beijing Jianghe Cloud Technology Co.,Ltd. (“BJ JHC”) (1) / (8) ​ November 17, 2020 ​ PRC ​ 100 % Provision of internet data center services Beijing Shuntou Green Energy Data Technology Co.,Ltd. (“BJ ST”) (1) / (8) ​ November 17, 2020 ​ PRC ​ 100 % Provision of internet data center services ​ 1. ORGANIZATION(CONTINUED) ​ Entity Date of Place of Percentage Principal activities ​ ​ ​ Direct ​ Variable Interest Entities (the “VIEs”): ​ ​ ​ ​ Beijing Yiyun Network Technology Co., Ltd. (“21Vianet Technology”) (1) / (2) ​ October 22, 2002 ​ PRC ​ — ​ Provision of internet data center services Beijing iJoy Information Technology Co., Ltd. (“BJ iJoy”) (1) / (2) ​ April 30, 2013 ​ PRC ​ — ​ Provision of internet data center, content delivery network services WiFire Network Technology (Beijing) Co., Ltd. (“WiFire Network”) (1) / (2) ​ April 1, 2014 ​ PRC ​ — ​ Provision of telecommunication services Shanghai Zhiyan Yunwei Technology Co.,Ltd. (“SH Zhiyan”) (1) / (2) ​ December 12, 2020 ​ PRC ​ — ​ Provision of telecommunication services ​ ​ ​ ​ ​ ​ ​ ​ ​ Held directly by 21Vianet Technology: ​ ​ ​ ​ Beijing 21Vianet Broad Band Data Center Co., Ltd. (“21Vianet Beijing”) (1) / (2) ​ March 15, 2006 ​ PRC ​ — ​ Provision of internet data center services ​ ​ ​ ​ ​ ​ ​ ​ ​ Held directly by 21Vianet Beijing: ​ ​ ​ ​ 21Vianet (Xi’an) Information Outsourcing Industry Park Services Co., Ltd. (“Xi’an Sub”) (1) / (2) ​ June 23, 2008 ​ PRC ​ — ​ Provision of internet data center services Langfang Xunchi Computer Data Processing Co., Ltd. (“LF Xunchi”) (1) / (2) ​ December 19, 2011 ​ PRC ​ — ​ Dormant company Beijing Yilong Xinda Technology Co., Ltd. (“Yilong Xinda”) (1) / (2) ​ August 6, 2010 ​ PRC ​ — ​ Provision of internet data center services Beijing Yichengtaihe Investment Co., Ltd. (“BJ Yichengtaihe”) (1) / (2) ​ September 30, 2014 ​ PRC ​ — ​ Provision of internet data center services Guangzhou Lianyun Big Data Co. Ltd. (“GZ Lianyun”) (1) / (2) ​ April 14, 2016 ​ PRC ​ — ​ Provision of internet data center services Beijing Xianghu Yunlian Technology Co., Ltd. (“Xianghu Yunlian”) (1) / (2) ​ November 7, 2018 ​ PRC ​ — ​ Provision of internet data center services Shanghai Hujiang Songlian Technology Co., Ltd. (“Hujiang Songlian”) (1) / (2) ​ December 17, 2018 ​ PRC ​ — ​ Provision of internet data center services Beijing Shuhai Hulian Technology Co., Ltd. (“BJ Shuhai”) (1) / (2) ​ January 2, 2019 ​ PRC ​ — ​ Provision of internet data center services Nantong Chenghong Cloud Computing Co., Ltd. (“NT Chenghong”) (1) / (2) ​ December 24, 2019 ​ PRC ​ — ​ Provision of internet data center services Shanghai Shuzhong Investment Management Co., Ltd. (“SH Shuzhong”) (1)/(2)/(5) ​ June 30, 2020 ​ PRC ​ — ​ Provision of internet data center services Sanhe Shulifang Information Technology Co., Ltd. (“Shulifang”) (1)/(2)/(6) ​ July 21, 2020 ​ PRC ​ — ​ Provision of internet data center services Langfang Huahai Internet Technology Co., Ltd. (“LF Huahai”) (1)/(2)/(7) ​ September 11, 2020 ​ PRC ​ — ​ Provision of internet data center services ​ 1. ORGANIZATION(CONTINUED) ​ Entity Date of Place of Percentage Principal activities ​ ​ ​ ​ Held directly by SH Zhiyan: ​ ​ ​ ​ Shanghai Blue Cloud Technology Co., Ltd. (“SH Blue Cloud”) (1) / (2) ​ March 21, 2013 ​ PRC ​ — Provision of Office 365 and Windows Azure platform services ​ ​ ​ ​ ​ ​ ​ ​ ​ Held directly by DYX and LF Xunchi: ​ ​ ​ ​ ​ ​ ​ ​ Shenzhen Diyixian Telecommunication Co., Ltd. (“SZ DYX”) (1) ​ August 10, 2014 ​ PRC ​ 100 % Provision of virtual private network services ​ (1) Collectively, the “PRC Subsidiaries”. (2) Collectively, the “Consolidated VIEs”. (3) On August 10, 2014, the Company and its subsidiary, LF Xunchi, acquired 100% equity interest of Dermot BVI and its subsidiaries (collectively referred to as “Dermot Entities”). (4) On August 20, 2019, the Company through its subsidiary, DRP Investment, became the sole shareholder in Shihua Holding 2 and its subsidiaries (Note 4). (5) On June 30, 2020, the Company through its subsidiary, Shanghai Shilian Technology Co., Ltd (“SH Shilian”), acquired 100% equity interest of SH Shuzhong (Note 4). (6) On July 21, 2020, the Company through its subsidiary, SH Shilian, acquired 100% equity interest of Shulifang (Note 4). (7) On September 11, 2020, the Company through its subsidiaries, SH Shilian and 21Vianet Venus International Investment Limited (“21Vianet Venus”), acquired 100% equity interest of LF Huahai (Note 4). (8) On November 17, 2020, the Company through its subsidiary, 21Vianet Saturn International Investment Limited (“21Vianet Saturn”) and Beijing Zhongshun Yongfeng Investment Consulting Co.,Ltd. (“YF WFOE”), acquired 100% equity interest of BJ JHC and BJ ST (Note 4). ​ 1. ORGANIZATION (CONTINUED) (b) PRC laws and regulations prohibit foreign ownership of internet and telecommunications-related businesses. To comply with these foreign ownership restrictions, the Company conducts its businesses in the PRC through its VIEs using contractual agreements (the “VIE Agreements”). The Company controls four VIEs, namely 21Vianet Technology, BJ iJoy, WiFire Network and SH Zhiyan as of December 31, 2020. The key terms of the VIE Agreements in relation to BJ iJoy, WiFire Network and SH Zhiyan are substantially similar to 21Vianet Technology, except for the terms separately disclosed as below. The equity interests of 21Vianet Technology are legally held by certain PRC individuals, including Chen Sheng, the Executive Chairman of Board of Directors of the Company and Zhang Jun (collectively the “Nominee Shareholders”. The following is a summary of the key terms of the VIE Agreements of 21Vianet Technology: Exclusive option agreement Pursuant to the exclusive option agreement entered into amongst 21Vianet China and the Nominee Shareholders of 21Vianet Technology, the Nominee Shareholders granted the Company or its designated party, an exclusive irrevocable option to purchase all or part of the equity interests held by the Nominee Shareholders in 21Vianet Technology, when and to the extent permitted under the PRC laws, at an amount equal to RMB1. 21Vianet Technology cannot declare any profit distributions or grant loans in any form without the prior written consent of 21Vianet China. The Nominee Shareholders must remit in full any funds received from 21Vianet Technology to 21Vianet China, in the event any distributions are made by 21Vianet Technology. The term of this agreement is 10 years, expiring on December 18, 2016, which is renewable at the sole discretion of 21Vianet China. On December 19, 2016, this agreement was renewed for another 10 years, expiring on December 18, 2026. SH Zhiyan has substantially similar exclusive option agreement except that the term of SH Zhiyan will terminate when SH Edge Connect, the primary beneficiary, purchases all of SH Zhiyan’s equity interest held by the Nominee Shareholder, Shanghai Rongyan Yunqi Technology Co.,Ltd. (“SH Rongyan”). Exclusive technical consulting and service agreement Pursuant to the exclusive technical consulting and service agreement entered into between 21Vianet China and 21Vianet Technology, 21Vianet China is to provide exclusive management consulting services and internet technical services in return for fees based on of a predetermined hourly rate of RMB1, which is adjustable at the sole discretion of 21Vianet China. The term of this agreement is 10 years, expiring on December 18, 2016, which is renewable at the sole discretion of 21Vianet China. On December 19, 2016, this agreement was renewed for another 10 years, expiring on December 18, 2026. SH Zhiyan has substantially similar exclusive technical consulting and service agreement except that the term for SH Zhiyan would be in effect for an unlimited term unless terminated in writing by SH Edge Connect, the primary beneficiary of VIE SH Zhiyan. ​ 1. ORGANIZATION (CONTINUED) Loan agreement In January 2011, 21Vianet China and the Nominee Shareholders entered into a loan agreement. Pursuant to the agreement, 21Vianet China has provided interest-free loan facilities of RMB7,000 and RMB3,000, respectively, to the Nominee Shareholders of 21Vianet Technology for the purpose of providing capital to 21Vianet Technology to develop its data center and telecommunications value-added business and related businesses. There is no fixed term for the loan. The Nominee Shareholders of SH Zhiyan did not enter into any loan agreement to fund the capital injected in SH Zhiyan. Power of attorney agreement The Nominee Shareholders entered into the power of attorney agreement whereby they granted an irrevocable proxy of the voting rights underlying their respective equity interests in 21Vianet Technology to 21Vianet China, which includes, but are not limited to, all the shareholders’ rights and voting rights empowered to the Nominee Shareholders by the company law and 21Vianet Technology’s Articles of Association. The power of attorney remains valid and irrevocable from the date of execution, so long as each Nominee Shareholder remains as a shareholder of 21Vianet Technology. The power of attorney agreement in relation to 21Vianet Technology was reassigned to 21Vianet Group, Inc. in September 2010. Share pledge agreement Pursuant to the share pledge agreement entered into amongst 21Vianet China, 21Vianet Technology and the Nominee Shareholders, the Nominee Shareholders have contemporaneously pledged all their equity interests in 21Vianet Technology to guarantee the repayment of the loan under the Loan Agreement between 21Vianet China and the Nominee Shareholders. On August 10, 2015, a Notification of Cancellation of share pledge registration was issued by Beijing Administration for Industry and Commerce, Pinggu Branch to cancel the registration of the share pledge by one of the Nominee Shareholders of 21Vianet Technology, Zhang Jun. Such cancellation does not affect the effectiveness of the share pledge agreement and does not lessen the control imposed on the contractual parties of the Company. If 21Vianet Technology breaches its respective contractual obligations under the Share pledge agreement and the loan agreement, 21Vianet China, as pledgee, will be entitled to certain rights, including the right to sell the pledged equity interests. The Nominee Shareholders agreed not to transfer, sell, pledge, dispose of or otherwise create any new encumbrance on their equity interests in 21Vianet Technology without the prior written consent of 21Vianet China. SH Zhiyan has substantially similar term the Nominee Shareholders of SH Zhiyan did not enter into any loan agreement to fund the capital injected in SH Zhiyan as mentioned above. ​ 1. ORGANIZATION (CONTINUED) Financial support letter Pursuant to the financial support letter, 21Vianet Group, Inc. agreed to provide unlimited financial support to 21Vianet Technology for its operations and agreed to forego the right to seek repayment in the event 21Vianet Technology is unable to repay such funding. SH Zhiyan has substantially similar term except that SH Edge Connect provides unlimited financial support to SH Zhiyan for its operations. Despite the lack of technical majority ownership, there exists a parent-subsidiary relationship between the Company and 21Vianet Technology through the irrevocable power of attorney agreement, whereby the Nominee Shareholders effectively assigned all of their voting rights underlying their equity interests in 21Vianet Technology to the Company. In addition, the Company, through 21Vianet China, obtained effective control over 21Vianet Technology through the ability to exercise all the rights of 21Vianet Technology’s shareholders pursuant to the share pledge agreement and exclusive option agreement. The Company demonstrates its ability and intention to continue to exercise the ability to absorb substantially all of the expected losses through the financial support letter. In addition, the Company also demonstrates its ability to receive substantially all of the economic benefits of 21Vianet Technology through 21Vianet China through the consulting and service agreement. Thus, the Company is the primary beneficiary of 21Vianet Technology and consolidates 21Vianet Technology and its subsidiaries under Accounting Standards Codification (“ASC”) Subtopic 810-10, Consolidation: Overall In the opinion of the Company’s management and PRC counsel, (i) the ownership structure of the VIEs is in compliance with applicable PRC laws and regulations in any material respect, and (ii) each of the VIE Agreements is valid, legally binding and enforceable to each party of such agreements under the existing PRC laws and will not violate any PRC laws or regulations currently in effect. However, there are substantial uncertainties regarding the interpretation and application of current and future PRC laws and regulations. Accordingly, the Company cannot be assured that PRC regulatory authorities will not ultimately take a contrary view to its opinion. If the current ownership structure of the Company and its contractual arrangements with the VIEs are found to be in violation of any existing or future PRC laws and regulations, the Company may be required to restructure its ownership structure and operations in the PRC to comply with the changing and new PRC laws and regulations. To the extent that changes and new PRC laws and regulations prohibit the Company’s VIE arrangements from complying with the principles of consolidation, the Company would have to deconsolidate the financial position and results of operations of its VIEs. In the opinion of management, the likelihood of loss in respect of the Company’s current ownership structure or the contractual arrangements with the VIEs is remote based on current facts and circumstances. ​ 1. ORGANIZATION (CONTINUED) (c) VIE disclosures Except for certain property with carrying amounts of RMB134,415 (US$20,600) that were pledged to secure banking borrowings granted to the Company (Note 13), there were no pledges or collateralization of the Consolidated VIEs’ assets. Creditors of the Consolidated VIEs have no recourse to the general credit of the primary beneficiaries of the Consolidated VIEs, and such amounts have been parenthetically presented on the face of the consolidated balance sheets. The Consolidated VIEs operate the data centers and own facilities including data center buildings, leasehold improvements, fiber optic cables, computers and network equipment, which are recognized in the Company’s consolidated financial statements. They also hold certain value-added technology licenses, registered copyrights, trademarks and registered domain names, including the official website, which are also considered as revenue-producing assets. However, none of such assets was recorded on the Company’s consolidated balance sheets as such assets were all acquired or internally developed with insignificant cost and expensed as incurred. In addition, the Company also hires data center operation and marketing workforce for its daily operations and such costs are expensed when incurred. The Company has not provided any financial or other support that it was not previously contractually required to provide to the Consolidated VIEs during the periods presented. (d) Cooperation with Waburg Pincus In March 2017, the Company entered into an investment agreement with Warburg Pincus to establish a multi-stage joint venture and build a digital real estate platform in China. The Company seeded the initial JV with four existing high-performing IDC assets, and Warburg Pincus contributed direct capital and extensive industry network and resources in the real estate sector. The Company owns 51% of the equity interests in the four existing internet data center (“IDC”) assets while Warburg Pincus owns the remaining 49%. On March 14, 2017, Shihua Investment was established by the Company and a subsidiary of Warburg Pincus, with the equity interest of 51% and 49%, respectively. In March 2017, the Company and Warburg Pincus set up two joint ventures, Shihua Holdings 2 and Shihua DC Investment Management Limited (“Shihua Investment Management”) (collectively, “Shihua DC Holdings”) (Note 12), with the equity interest of 49% and 51%, respectively. The Company accounted for the investment in the two joint ventures under equity method investments for its ability to exercise significant influence. In July 2019, the Company entered into restructuring agreements with Warburg Pincus. Pursuant to the restructuring agreement, Shihua Holdings 2 transferred 100% of the equity interest in some subsidiaries at the consideration equivalent to the subsidiaries’ paid-in capital to Warburg Pincus. Thereafter, Shihua Holdings 2 repurchased and cancelled all Warburg Pincus’s shares in Shihua Holdings 2. Upon completion of restructuring on August 20, 2019, the Company became the sole shareholder in Shihua Holdings 2, which was accounted for as an asset acquisition (Note 4). 1. ORGANIZATION (CONTINUED) The following tables represent the financial information of the Consolidated VIEs as of December 31, 2019 and 2020 and for the years ended December 31, 2018, 2019 and 2020 before eliminating the intercompany balances and transactions between the Consolidated VIEs and other entities within the Company: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ ASSETS ​ ​ ​ ​ ​ ​ Current assets: Cash and cash equivalents 591,503 737,556 113,035 Restricted cash 260,961 260,450 39,916 Accounts receivable (net of allowance for doubtful debt of RMB66,416 and RMB67,632 (US$10,365) as of December 31, 2019 and 2020, respectively) 513,440 664,610 101,856 Prepaid expenses and other current assets 1,371,564 1,622,662 248,684 Amounts due from related parties 57,982 12,968 1,987 Total current assets 2,795,450 3,298,246 505,478 Non-current assets: ​ ​ Property and equipment, net 3,580,341 5,170,878 792,472 Intangible assets, net 151,722 342,288 52,458 Land use rights, net 58,588 46,719 7,160 Operating lease right-of-use assets, net ​ 1,144,846 ​ 1,134,073 ​ 173,804 Goodwill 302,647 308,110 47,220 Restricted cash 66,119 27,719 4,248 Deferred tax assets, net 180,959 168,181 25,775 Amounts due from related parties 20,654 20,562 3,151 Other non-current assets 262,685 435,144 66,689 Long-term investments, net 189,571 172,593 26,451 Total non-current assets 5,958,132 7,826,267 1,199,428 Total assets 8,753,582 11,124,513 1,704,906 Current liabilities: ​ ​ Short-term bank borrowings 232,323 34,000 5,211 Accounts payable and notes payable 211,710 182,669 27,995 Accrued expenses and other payables 622,160 981,961 150,492 Advance from customers 1,068,692 1,041,594 159,631 Deferred revenue 52,088 58,066 8,899 Income tax payable 8,175 12,743 1,953 Amounts due to inter-companies (1) 2,786,838 4,248,422 651,099 Amounts due to related parties 56,977 50,193 7,692 Current portion of finance lease liabilities 220,363 362,760 55,595 Current portion of long-term borrowings 32,500 165,328 25,338 Current portion of deferred government grant 2,595 2,074 318 Current portion of operating lease liabilities ​ 410,422 ​ 427,114 ​ 65,458 Total current liabilities 5,704,843 7,566,924 1,159,681 ​ 1. ORGANIZATION (CONTINUED) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Non-current liabilities: ​ ​ ​ ​ ​ ​ Amounts due to inter-companies (1) 1,020,972 1,020,972 156,471 Amounts due to related parties 745,899 747,746 114,597 Long-term borrowings 79,500 570,135 87,377 Non-current portion of finance lease liabilities 549,669 299,399 45,885 Unrecognized tax benefits 1,991 68,317 10,470 Deferred tax liabilities 82,725 155,281 23,798 Non-current portion of deferred government grant 5,906 4,100 628 Non-current portion of operating lease liabilities ​ 529,546 ​ 497,268 ​ 76,210 Total non-current liabilities 3,016,208 3,363,218 515,436 Total liabilities 8,721,051 10,930,142 1,675,117 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Net revenues 2,532,854 2,858,176 3,885,141 595,424 Net profit 52,986 111,592 73,748 11,302 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Net cash generated from operating activities 693,620 495,308 748,418 114,700 Net cash generated from (used in) investing activities 132,522 (1,247,764) (1,943,358) (297,833) Net cash (used in) generated from financing activities (423,467) 885,286 1,302,082 199,553 Net increase in cash and cash equivalents and restricted cash 402,705 132,830 107,142 16,420 ​ (1) Amounts due to inter-companies consist of intercompany payables to the other companies within the Company for the purchase of telecommunication resources and property and equipment on behalf of the Consolidated VIEs.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2020
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (a) Basis of presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). (b) Principles of consolidation The consolidated financial statements include the financial statements of the Company, its subsidiaries and the Consolidated VIEs for which the Company or a subsidiary of the Company is the primary beneficiary. All significant inter-company transactions and balances between the Company, its subsidiaries and the Consolidated VIEs are eliminated upon consolidation. Results of acquired subsidiaries and its Consolidated VIEs are consolidated from the date on which control is transferred to the Company. (c) Use of estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the period. Significant estimates and assumptions reflected in the Company’s financial statements include, but are not limited to, determining the valuation allowance for deferred tax assets, determining the fair value of convertible promissory notes and assessing the initial valuation of the assets acquired and liabilities assumed in acquisitions. Changes in facts and circumstances may result in revised estimates. Given the global economic climate and unforeseen effects from COVID-19 pandemic, the process of estimation has become more challenging. Actual results could differ from those estimates, and as such, differences may be material to the consolidated financial statements. (d) Foreign currency The functional currency of the Company and its overseas subsidiaries is the United States dollar (“US$”), whereas the functional currency of the Company’s PRC subsidiaries and its Consolidated VIEs is the Chinese Renminbi (“RMB”) as determined based on the criteria of ASC Topic 830, Foreign Currency Matters The financial statements of the Company and its overseas subsidiaries are translated from the functional currency to the reporting currency, RMB. Transactions denominated in foreign currencies are re-measured into the functional currency at the exchange rates prevailing on the transaction dates. Monetary assets and liabilities denominated in foreign currencies are re-measured at the exchange rates prevailing at the balance sheet date. Non-monetary items that are measured in terms of historical costs in foreign currency are re-measured using the exchange rates at the dates of the initial transactions. Exchange gains and losses are included in the consolidated statements of operations. The Company uses the average exchange rate for the year and the exchange rate at the balance sheet date to translate the operating results and financial position, respectively. Translation differences are recorded in accumulated other comprehensive income (loss) within the statements of comprehensive loss. (e) Convenience translation Amounts in US$ are presented for the convenience of the reader and are translated at the noon buying rate of US$1.00 to RMB6.5250 on December 31, 2020, the last business day in fiscal year 2020, representing the noon buying rate set forth in the H.10 statistical release of the U.S. Federal Reserve Board. No representation is made that the RMB amounts could have been, or could be converted, realized or settled into US$ at such rate or at any other rate. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (f) Cash and cash equivalents Cash and cash equivalents consist of cash on hand and demand deposits placed with banks which are unrestricted as to withdrawal and use and have original maturities less than three months. All highly liquid investments with a stated maturity of 90 days or less from the date of purchase are classified as cash equivalents. (g) Restricted cash Restricted cash mainly represents amounts held by a few banks in escrow as security for credit facilities, the guarantee of compliance with the network and service requirements of the radio spectrum license awarded by the Hong Kong Telecommunication Authority, the deposits for finance lease, the deposits for a lawsuit with a third party, the deposits held in escrow for the advances received from end customers subscribing Office 365 and Windows Azure services (the disbursement of which shall be agreed by both Microsoft (China) Co., Ltd. (“Microsoft”) and the Company), the deposits for business operation, the deposits for loans. (h) Short-term investments All highly liquid investments with original maturities of greater than three months but less than twelve months, are classified as short-term investments. Interest income is included in earnings. (i) Accounts receivable and allowance for doubtful debt Prior to adopting ASC 326, Financial Instruments-Credit Losses Receivables On January 1, 2020, the Company adopted ASC326 using modified-retrospective transition approach. Following the adoption of this guidance, a cumulative-effect adjustment in accumulated deficit of RMB2,740 was recognized as of January 1, 2020. For the year ended December 31, 2020, the Company recorded credit losses of RMB2,393 (US$367). Pursuant to ASC 326, an allowance for credit losses for financial assets, including accounts receivable, carried at amortized cost to present the net amount expected to be collected as of the balance sheet date. Such allowance is based on credit losses expected to arise over the life of the asset’s contractual term, which includes consideration of prepayments. Assets are written off when the Company determines that such financial assets are deemed uncollectible and are recognized as a deduction from the allowance for credit losses. Expected recoveries of amounts previously written off, not to exceed the aggregate of the amount previously written off, are included in determining the necessary reserve at the balance sheet date. The Company pools financial assets based on similar risk characteristics to estimate expected credit losses. The Company estimates expected credit losses on financial assets individually when those assets do not share similar risk characteristics. The Company closely monitors its accounts receivable including timely account reconciliations, detailed reviews of past due accounts, updated credit limits, and monthly analysis of the adequacy of their reserve for credit losses. The Company utilizes a loss rate approach to determine lifetime expected credit losses for its financial assets. This method is used for calculating an estimate of losses based primarily on the Company’s historical loss experience. In determining loss rates, the Company evaluates information related to historical losses, adjusted for current conditions and further adjusted for the period of time that the Company can reasonably forecast. The Company has concluded that it can reasonably support a forecast period for the contractual life of its financial assets. Qualitative and quantitative adjustments related to current conditions and the reasonable and supportable forecast period consider the following: the customer or vendor ’s creditworthiness, changes in the policy and procedures to establish customer credit limits, changes in the payment terms of receivables, existence and effect of any concentration of credit and changes in the level of such concentrations, and the effects of other external forces such as the current and forecasted direction of the economic and business environment. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (j) Property and equipment Property and equipment are stated at cost less accumulated depreciation and any recorded impairment. Property and equipment acquired in a business combination are recognized initially at fair value at the data of acquisition. Property and equipment are depreciated using the straight-line method over the estimated useful lives of the assets, as follows: ​ ​ ​ ​ Category Estimated useful life Property 25-46 years Leasehold improvements Over the shorter of lease term or the estimated useful lives of the assets Optical fibers 10-20 years Computer and network equipment 1-10 years Office equipment 2-8 years Motor vehicles 2-8 years ​ Repair and maintenance costs are charged to expense as incurred, whereas the costs of betterments that extend the useful life of property and equipment are capitalized as additions to the related assets. Retirements, sale and disposals of assets are recorded by removing the cost and accumulated depreciation with any resulting gain or loss reflected in the consolidated statements of operations. Property and equipment that are purchased or constructed which require a period of time before the assets are ready for their intended use are accounted for as construction-in-progress. Construction-in-progress is recorded at acquisition cost, including installation costs. Construction-in-progress is transferred to specific property and equipment accounts and commences depreciation when these assets are ready for their intended use. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (k) Intangible assets Intangible assets are carried at cost less accumulated amortization and any recorded impairment. Intangible assets acquired in a business combination are recognized initially at fair value at the date of acquisition. Intangible assets with finite useful lives are amortized using a straight-line method. These amortization methods reflect the estimated pattern in which the economic benefits of the respective intangible assets are to be consumed. The Company has capitalized certain internal use software development costs in accordance with ASC Subtopic 350-40, Intangibles-Goodwill and Other: Internal-Use Software Intangible assets have weighted average useful lives from the date of purchase/ acquisition as follows: ​ ​ ​ ​ Purchased software 5.1 years Radio spectrum license 15 years Operating permits* ​ 29.3 years Contract backlog* 4.9 years Customer relationships* 8.8 years Licenses* 15 years Supplier relationships* 10 years Trade Names* 20 years Platform software* 5 years Non-complete agreements* 5 years Internal use software 3.8 years Customer contract* ​ 6.5 years ​ * Acquired in the acquisitions of subsidiaries. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (l) Leases Effective January 1, 2019, the Company adopted ASC Topic 842, Lease The Company has elected the package of practical expedients, which allows the Company not to reassess (1) whether any expired or existing contracts as of the adoption date are or contain a lease, (2) lease classification for any expired or existing leases as of the adoption date and (3) initial direct costs for any expired or existing leases as of the adoption date. The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. Lastly, the Company elected the short-term lease exemption for all contracts with lease term of 12 months or less. At the commencement date of a lease, the Company determines the classification of the lease based on the relevant factors present and records a right-of-use (“ROU”) asset and lease liability for operating lease, and records property and equipment and finance lease liability for finance lease. ROU assets and property and equipment acquired through lease represent the right to use an underlying asset for the lease term, and operating lease liabilities and finance lease liabilities represent the obligation to make lease payments arising from the lease. ROU assets and lease liabilities are calculated as the present value of the lease payments not yet paid. If the rate implicit in the Company’s leases is not readily available, the Company uses an incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. This incremental borrowing rate reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. ROU assets include any lease prepayments and are reduced by lease incentives. Operating lease expense for lease payments is recognized on a straight-line basis over the lease term. Lease terms are based on the non-cancelable term of the lease and may contain options to extend the lease when it is reasonably certain that the Company will exercise that option. Leases with an initial lease term of 12 months or less are not recorded on the consolidated balance sheets. Lease expense for these leases is recognized on a straight-line basis over the lease term. (m) Land use right The land use rights represent the operating lease prepayments for the rights to use the land in the PRC under ASC 842. Amortization of the prepayments is provided on a straight-line basis over the terms of the respective land use rights certificates. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (n) Long-term investments The Company’s long-term investments primarily consist of equity investments without readily determinable fair value, equity method investments. Pursuant to ASC Topic 321, Investments—Equity Securities Fair Value Measurements and Disclosures For equity investments measured at fair value with changes in fair value recorded in earnings, the Company does not assess whether those securities are impaired. For those equity investments that the Company elects to use the measurement alternative, the Company makes a qualitative assessment of whether the investment is impaired at each reporting date. If a qualitative assessment indicates that the investment is impaired, the entity has to estimate the investment’s fair value in accordance with the principles of ASC 820. If the fair value is less than the investment’s carrying value, the entity has to recognize an impairment loss in net loss equal to the difference between the carrying value and fair value. Investments in equity investees represent investments in entities in which the Company can exercise significant influence but does not own a majority equity interest or control are accounted for using the equity method of accounting in accordance with ASC Subtopic 323-10, Investments-Equity Method and Joint Ventures: Overall (o) Goodwill Goodwill represents the excess of the purchase price over the amounts assigned to the fair value of the assets acquired and the liabilities assumed of an acquired business. In accordance with ASC Topic 350, Goodwill and Other Intangible Assets In accordance with ASC 350, the Company assigned and assessed goodwill for impairment at the reporting unit level. A reporting unit is an operating segment or one level below the operating segment. As of December 31, 2018, 2019 and 2020, there is only hosting and related services and the Company as a whole is one reporting unit. Pursuant to ASC 350, in 2019 and 2020, the Company performed a qualitative assessment for hosting and related services and completed its annual impairment test for goodwill that has arisen out of its acquisitions. The Company evaluated all relevant factors including, but not limited to, macroeconomic conditions, industry and market conditions, financial performance, and the share price of the Company. The Company weighed all factors in their entirety and concluded that it was not more-likely-than-not the fair value was less than the carrying amount of the reporting unit, and further impairment testing on goodwill was unnecessary. No impairment loss of goodwill in hosting and related services was recognized for the years ended December 31, 2018, 2019 and 2020. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (p) Impairment of long-lived assets The Company evaluates long-lived assets, such as fixed assets and purchased or internally developed intangible assets with finite lives for impairment whenever events or changes in circumstances indicate the carrying value of an asset may not be recoverable in accordance with ASC Topic 360, Property, Plant and Equipment . When such events occur, the Company assesses the recoverability of the asset group based on the undiscounted future cash flows the asset group is expected to generate and recognizes an impairment loss when estimated undiscounted future cash flows expected to result from the use of the asset group plus net proceeds expected from disposition of the asset group, if any, is less than the carrying value of the asset group. If the Company identifies an impairment, the Company reduces the carrying amount of the asset group to its estimated fair value based on a discounted cash flow approach or, when available and appropriate, to comparable market values and the impairment loss, if any, is recognized in the consolidated statements of operations. As of December 31, 2020, due to continuing losses, the Company recorded the long-lived assets impairment amounting to RMB81,619 (US$12,509) for one of its asset groups, resulting from excess of the carrying amount of the asset group over the fair value of the asset group. The Company determined the fair value of the asset group using the income approach based on the discounted cash flows associated with the asset group. The discounted cash flows were based on a six-year projection for the asset group, which is consistent with the remaining useful life of its principal asset. The discount rate of 13% was derived and used in the valuations which reflect the market assessment of the risks specific to the Company and its industry and is based on its weighted average cost of capital. No impairment was recognized in other asset groups as there was no impairment indicator identified. The impairment loss reduced the carrying amount of the long-lived assets of the group on a pro-rata basis using the relative carrying amount of those assets except that the loss allocated to an individual long-lived asset of the group shall not reduce the carrying amount of that asset below its fair value whenever that fair value is determinable without undue cost and effort. The Company recorded impairment charges associated with its long-lived assets and acquired intangibles as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Impairment of equipment — — 35,793 5,486 Impairment of intangible assets — — 38,654 5,924 Impairment of other non-current assets — — 7,172 1,099 ​ ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (q) Fair value of financial instruments The Company’s financial instruments include cash and cash equivalents, restricted cash, short-term investments, accounts receivable and payable, other receivables and payables, bonds payable, short-term and long-term borrowings, available-for-sale investments, liability classified restricted share units (“RSU”) and convertible promissory notes. Other than the bonds payable, long-term borrowings and convertible promissory notes, the carrying values of these financial instruments approximate their fair values due to their short-term maturities. The carrying amounts of bonds payable and long-term borrowings approximate their fair values since they bear interest rates which approximate market interest rates. The Company carries the bonds payable at face value less unamortized debt discount and issuance cost on its consolidated balance sheets and measures the fair value for disclosure purposes only. The Company elected the fair value option of convertible promissory notes when it initially recognized as financial liability as the fair value better represents the value of the underlying liabilities. The contingent purchase considerations in both cash and shares and share-settled bonus are initially measured at fair value on the acquisition dates of the acquired businesses and the date of grant, respectively, and subsequently remeasured at the end of each reporting period with an adjustment for fair value recorded to the current period income/(expense). Convertible promissory notes are measured at fair value in accordance with ASC 825, Financial Instruments (r) Revenue recognition The Company provides hosting and related services including hosting of customers’ servers and networking equipment, connecting customers’ servers with internet backbones (“Hosting service”), virtual private network services providing encrypted secured connection to public internet (“VPN service”) and other value-added services and public cloud service through strategic partnership with Microsoft. On January 1, 2018, the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers Revenue Recognition Under ASC 606, an entity recognizes revenue as the Company satisfies a performance obligation when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. Once a contract is determined to be within the scope of ASC 606 at contract inception, the Company reviews the contract to determine which performance obligations it must deliver and which of these performance obligations are distinct. The Company recognizes revenue based on the amount of the transaction price that is allocated to each performance obligation when that performance obligation is satisfied or as it is satisfied. The Company is a principal and records revenue on a gross basis when the Company is primarily responsible for fulfilling the service, has discretion in establishing pricing and controls the promised service before transferring that service to customers. Otherwise, the Company records revenue at the net amounts as commissions. 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (r) Revenue recognition (continued) The Company’s revenue recognition policies effective on the adoption date of ASC 606 are as follows: Hosting services are services that the Company dedicates data center space to house customers’ servers and networking equipment and provides tailored server administration services including operating system support and assistance with updates, server monitoring, server backup and restoration, server security evaluation, firewall services, and disaster recovery. The Company also provides interconnectivity services to connect customers with each other, internet backbones in China and other networks through Border Gateway Protocol, or BGP, network, or single-line, dual-line or multiple-line networks. Hosting services are typically provided to customers for a fixed amount over the contract service period and the related revenues are recognized on a straight-line basis over the term of the contract. For certain contracts where considerations are based on the usage of the Hosting services, the related revenues are recognized based on the consumption at the predetermined rate as the services are rendered throughout the contact term. The Company is a principal and records revenue for Hosting service on a gross basis. VPN services are services that the Company extends customers’ private networks by setting up secure and dedicated connections through the public internet. VPN services are provided to customers for a fixed amount over the contract service period and revenue are recognized on a straight-line basis over the term of the contract. The Company is a principal and records revenue for VPN service on a gross basis. The Company partners with Microsoft to provide Cloud services that allow enterprise and individual customers to run their applications over the internet using the IT infrastructure. Cloud services are generally charged by the Company to the end customers for a fixed amount or based on the actual usage of the cloud resources at predetermined rates over the subscription period, which in general is one year. The Company fulfils its performance obligation of facilitating Microsoft to provide the Cloud services to the end customers by providing, but not limited to, contract processing management, billing, payment collection, maintenance, help desk supports and certain IT infrastructure services. These are considered as a series of distinct services that are substantially the same and have the same pattern of transfer to the customer; therefore, they are accounted for as a single performance obligation that is satisfied over time. The corresponding consideration that the Company is entitled to is recognized as revenue using a time-based method since this best depicts the pattern of the control transfer. Revenue from Cloud services consists of monthly incentive revenues received from Microsoft upon completion of certain conditions and gross billing amount received from end customers net of considerations remitted by the Company to Microsoft. When the contract is modified to add distinct services to the single performance obligation for additional fees, such changes are accounted for prospectively as a termination of the old contract and the creation of a new contract. For certain arrangements, customers are required to pay the Company before the services are delivered. When either party to a revenue contract has performed, the Company recognizes a contract asset or a contract liability in the consolidated balance sheets, depending on the relationship between the Company’s performance and the customer’s payment. Contract liabilities were mainly related to fee received for Hosting services to be provided over the contract period, which were presented as deferred revenue on the consolidated balance sheets. Deferred revenue represented the Company’s obligation to transfer the goods or services to a customer for which the Company has received consideration (or an amount of consideration is due) from the customer. As of December 31, 2019 and 2020, the Company has deferred revenue amounting up to RMB57,625 and RMB63,245 (US$9,693), respectively. Revenue recognized from opening deferred revenue balance was RMB46,730 (US$7,162) for the year ended December 31, 2020. The Company’s certain Hosting service contains lease and non-lease components. The Company elected to adopt the practical expedient which allows lessors to combine lease and non-lease components and account for them as one component if 1) the timing and pattern of transfer of the lease component and non-lease component is the same; 2) the lease component should be classified as an operating lease if it were accounted for separately. The combined component is accounted for in accordance with the current lease accounting guidance (“ASC 842”) if the lease component is predominant, and in accordance with the ASC 606 if the non-lease component is predominant. The Company has determined that the non-lease component is the predominant component in Hosting service. Therefore, the Company has accounted for the combined component in accordance with ASC 606. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (r) Revenue recognition (continued) The Company does not disclose the value of unsatisfied performance obligations as the Company’s revenue contracts are (i) contracts with an original expected length of one year or less or (ii) contracts for which the Company recognizes revenue at the amount to which it has the right to invoice for services performed. (s) Cost of revenues Cost of revenues consists primarily of telecommunication costs, depreciation of the Company’s long-lived assets, amortization of acquired intangible assets, maintenance, data center rental expenses directly attributable to the provision of the IDC services, payroll and other related costs of operations. (t) Advertising expenditures Advertising expenditures are expensed as incurred and are included in sales and marketing expenses, which amounted to RMB7,968, RMB6,095 and RMB7,779 (US$1,192) for the years ended December 31, 2018, 2019 and 2020, respectively. (u) Research and development expenses Research and development expenses consist primarily of payroll and related personnel costs for routine upgrades and related enhancements of the Company’s services and network. Research and development expenses are expensed as incurred except for costs to develop internal-use software or add significant upgrades and enhancements resulting in additional functionality to internal-use software that meet the capitalization criteria in accordance with ASC Subtopic 350-40, Intangibles-Goodwill and Other, Internal-Use Software (v) Government grants Government grants are provided by the relevant PRC municipal government authorities to subsidize the cost of certain research and development projects. The amount of such government grants is determined solely at the discretion of the relevant government authorities and there is no assurance that the Company will continue to receive these government grants in the future. Government grants are recognized when it is probable that the Company will comply with the conditions attached to them, and the grants are received. When the grant relates to an expense item, it is recognized in the consolidated statement of operations over the period necessary to match the grant on a systematic basis to the costs that it is intended to compensate, as a reduction of the related operating expense. When the grant relates to an asset, it is recognized as deferred government grants and released to the consolidated statement of operations in equal amounts over the expected useful life of the related asset, when operational, as a reduction of the related depreciation expense. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (w) Capitalized interest Interest costs are capitalized if they are incurred during the acquisition, construction or production of a qualifying asset and such costs could have been avoided if expenditures for these assets have not been made. As a result of total interest costs capitalized during the period, the interest expense for the years ended December 31, 2018, 2019 and 2020, was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Interest expense and amortization cost of bonds payable 150,098 223,832 223,785 34,297 Interest expense on convertible promissory notes ​ — ​ — ​ 18,880 ​ 2,893 Interest expense on bank and other borrowings 19,395 14,212 39,424 6,042 Interest expense on finance leases 79,935 120,185 130,196 19,953 Total interest costs 249,428 358,229 412,285 63,185 Less: Total interest costs capitalized (13,362) (12,274) (31,676) (4,854) Interest expense, net 236,066 345,955 380,609 58,331 ​ (x) Income taxes The Company accounts for income taxes using the liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and tax bases of assets and liabilities using enacted tax rates that will be in effect in the period in which the differences are expected to reverse. The carrying amount of deferred tax assets is reviewed on an entity-by-entity basis and is reduced by a valuation allowance to the extent that it is more-likely-than-not that the benefits of the deferred tax assets will not be realized in future years. The valuation allowance is determined based on the weight of positive and negative evidences including future reversals of existing taxable temporary differences, the adequacy of future taxable income exclusive of reversing temporary differences, and verifiable tax planning. The estimated future taxable income involves significant assumptions of forecasted revenue growth that take into consideration of the Company’s historical financial results, its plan of expanding operating capacity as well as current industry trends. The effect on deferred taxes of a change in tax rate

CONCENTRATION OF RISKS

CONCENTRATION OF RISKS	12 Months Ended
	Dec. 31, 2020
CONCENTRATION OF RISKS
CONCENTRATION OF RISKS	3. CONCENTRATION OF RISKS (a) Credit risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents, short-term investments, accounts receivable, other receivables and amounts due from related parties. As of December 31, 2019 and 2020, the aggregate amount of cash and cash equivalents, restricted cash and short-term investments of RMB1,171,075 and RMB1,419,855 (US$217,602), respectively, were held at major financial institutions located in the PRC, and US$222,638 and US$303,824 (RMB1,982,454), respectively, were deposited with major financial institutions located outside the PRC. Management believes that these financial institutions are of high credit quality and continually monitors the credit worthiness of these financial institutions. Historically, deposits in Chinese banks are secure due to the state policy on protecting depositors’ interests. However, China promulgated a new Bankruptcy Law in August 2006 that came into effect on June 1, 2007, which contains a separate article expressly stating that the State Council may promulgate implementation measures for the bankruptcy of Chinese banks based on the Bankruptcy Law. Under the new Bankruptcy Law, a Chinese bank may go into bankruptcy. In addition, since China’s concession to the World Trade Organization, foreign banks have been gradually permitted to operate in China and have been significant competitors against Chinese banks in many aspects, especially since the opening of the Renminbi business to foreign banks in late 2006. Therefore, the risk of bankruptcy of those Chinese banks in which the Company has deposits has increased. In the event of bankruptcy of one of the banks which holds the Company’s deposits, the Company is unlikely to claim its deposits back in full since the bank is unlikely to be classified as a secured creditor based on PRC laws. (b) Business, supplier, customer, and economic risk The Company participates in a relatively dynamic and competitive industry that is heavily reliant operation excellence of the services. The Company believes that changes in any of the following areas could have a material adverse effect on the Company’s future financial position, result of operations or cash flows: (i) ​ 3. CONCENTRATION OF RISKS (CONTINUED) (b) Business, supplier, customer, and economic risk (continued) (ii) (iii) (iv) (v) ​ 3. CONCENTRATION OF RISKS (CONTINUED) (c) Currency convertibility risk The Company transacts substantially all its business in RMB, which is not freely convertible into foreign currencies. On January 1, 1994, the PRC government abolished the dual-rate system and introduced a single rate of exchange as quoted daily by the People’s Bank of China (the “PBOC”). However, the unification of the exchange rates does not imply that the RMB may be readily convertible into US$ or other foreign currencies. All foreign exchange transactions continue to take place either through the PBOC or other banks authorized to buy and sell foreign currencies at the exchange rates quoted by the PBOC. Approval of foreign currency payments by the PBOC or other institutions requires submitting a payment application form together with suppliers’ invoices, shipping documents and signed contracts. (d) Foreign currency exchange rate risk From July 21, 2005, the RMB is permitted to fluctuate within a narrow and managed band against a basket of certain foreign currencies. The depreciation (appreciation) of the RMB against US$ was approximately 5.0%, 1.6% and (6.5%) in the years ended December 31, 2018, 2019 and 2020, respectively. (e) Interest rate risk The Company is exposed to interest rate risk on its interest-bearing assets and liabilities. As part of its asset and liability risk management, the Company reviews and takes appropriate steps to manage its interest rate exposures on its interest-bearing assets and liabilities. The Company has not been exposed to material risks due to changes in market interest rates, and not used any derivative financial instruments to manage the interest risk exposure during the periods presented.

ACQUISITION AND DISPOSAL OF SUB

ACQUISITION AND DISPOSAL OF SUBSIDIARIES	12 Months Ended
	Dec. 31, 2020
ACQUISITION AND DISPOSAL OF SUBSIDIARIES
ACQUISITION AND DISPOSAL OF SUBSIDIARIES	4. ACQUISITION AND DISPOSAL OF SUBSIDIARIES Acquisitions in 2020 BJ JHC On November 17, 2020, the Company through its subsidiaries, YF WOFE and 21Vianet Saturn, acquired 100% equity interests in Splendid Oriental Limited (“Splendid”) which controls BJ JHC and its subsidiary BJ ST at a total cash consideration of RMB 432,015 (US$ 66,209 ). Among which, RMB 200,000 (US$ 30,651 ) is refundable if certain conditions are not achieved and is accounted as contingent consideration. The purpose of the transaction is to establish a new data center. As Splendid, BJ JHC and BJ ST do not possess all the elements that are necessary to conduct normal operations as a business and had not yet commenced operations, such acquisition is accounted for as an acquisition of assets. As of December 31, 2020, certain conditions in relation to RMB 200,000 (US$ 30,651 ) are not met and the corresponding asset is not recognized until the contingency is resolved. The carrying amount of the net identifiable assets were as follows: ​ ​ ​ ​ ​ ​ ​ RMB US$ Net assets acquired: ​ ​ Property and equipment, net 279,556 42,843 Operating permits (Note 9) 110,418 16,922 Customer contract (Note 9) 33,208 5,089 Operating lease right-of-use assets, net 112,398 17,226 Deferred tax assets 3,150 483 Other non-current assets 4,428 678 Cash and cash equivalents 30,319 4,647 Other current assets 8,833 1,354 Other current liabilities (90,805) (13,916) Operating lease liabilities (120,120) (18,409) Finance lease liabilities (84,082) (12,886) Deferred tax liabilities (55,288) (8,473) Total consideration in cash 232,015 35,558 ​ As of December 31, 2020, the Company, through its subsidiaries, YF WOFE and 21Vianet Saturn, made prepayments amounting to RMB844,309 (US$129,396) to acquire potential equity interests for the purpose of establishing data centers. As the closing conditions have not been achieved and the prepayments were refundable if acquisition is not completed, the prepayments were recorded as other non-current assets on the consolidated balance sheet as of December 31, 2020. ​ 4. ACQUISITION AND DISPOSAL OF SUBSIDIARIES (CONTINUED) Acquisition in 2020 (continued) SH Shuzhong On June 30, 2020, as part of its business strategy to expand the existing hosting service, the Company through its subsidiary, SH Shilian, acquired 100% of the equity interests in SH Shuzhong which primarily provides internet data center service from a third party selling shareholder, for a total cash consideration of RMB36,667 (US$5,619). As SH Shuzhong is in operations and possess all the elements that are necessary to conduct normal operations as a business, such acquisition is accounted for as business combination. The initial accounting is incomplete as certain liabilities are provisional. The following table summarizes the estimated fair values of the assets acquired and liabilities assumed as of the date of acquisition: ​ ​ ​ ​ ​ ​ ​ RMB US$ Property and equipment, net 348,475 53,406 Operating lease right-of-use assets, net 81,034 12,419 Customer contract (Note 9) 33,500 5,134 Purchased software 23 4 Deferred tax assets 14,848 2,275 Other non-current assets 1,685 258 Other current assets 44,774 6,862 Total assets acquired 524,339 80,358 Other current liabilities (406,932) (62,365) Operating lease liabilities (45,034) (6,902) Deferred tax liabilities (41,169) (6,309) Total liabilities assumed (493,135) (75,576) Net assets acquired 31,204 4,782 Purchase consideration 36,667 5,619 Goodwill 5,463 837 ​ The revenue and net profit since the acquisition date included in the consolidated statement of operations for the year ended December 31, 2020 were RMB41,928 (US$6,426) and RMB5,579 (US$855), respectively. The goodwill, which is not tax deductible, is primarily attributable to synergies expected to be achieved from the acquisition. ​ 4. ACQUISITION AND DISPOSAL OF SUBSIDIARIES (CONTINUED) Acquisition in 2020 (continued) Shulifang On June 24, 2020, the Company through its subsidiary, SH Shilian, entered into a share purchase agreement to acquire 100% equity interests in Shulifang at a total cash consideration of RMB43,000 (US$6,590) in installment upon achievement of certain conditions which is accounted as contingent consideration and the corresponding asset will only be recognized when the contingency is resolved. The purpose is to establish a new data center. As Shulifang does not possess all the elements that are necessary to conduct normal operations as a business and had not yet commenced operations, such acquisition is accounted for as an acquisition of assets. The transaction was closed on July 21, 2020. As of December 31, 2020, the condition of the last contingent consideration amounted to RMB10,000 (US$1,533) was not yet met. The contingent consideration obligation is not accounted for until the contingency is resolved. Carrying amount of the net identifiable assets of Shulifang were as follows: ​ ​ ​ ​ ​ ​ ​ RMB US$ Net assets acquired: ​ ​ Operating permits (Note 9) 45,134 6,917 Operating lease right-of-use assets, net 15,206 2,330 Other non-current assets 15,409 2,362 Cash and cash equivalents 53 8 Other current assets 601 91 Operating lease liabilities (15,206) (2,330) Other current liabilities (16,913) (2,592) Deferred tax liabilities (11,284) (1,729) Total consideration in cash 33,000 5,057 ​ LF Huahai On September 11, 2020 and October 28, 2020, the Company through its subsidiaries, SH Shilian and 21Vianet Venus International Investment Limited (“21Vianet Venus”), acquired 69.93% and 30.07% equity interests in LF Huahai at a total cash consideration of RMB59,500 (US$9,119) and RMB25,500 (US$3,908), respectively. The purpose is to establish a new data center with the acquired property. As LF Huahai does not possess all the elements that are necessary to conduct normal operations as a business and had not yet commenced operations, such acquisition is accounted for as an acquisition of assets. Carrying amount of the net identifiable assets of LF Huahai were as follows: ​ ​ ​ ​ ​ ​ ​ RMB US$ Net assets acquired: ​ ​ Operating permits (Note 9) 119,352 18,291 Operating lease right-of-use assets, net 183,174 28,073 Other non-current assets 27,524 4,218 Cash and cash equivalents 173 27 Other current assets 4,088 627 Other current liabilities (35,600) (5,456) Operating lease liabilities (183,873) (28,180) Deferred tax liabilities (29,838) (4,573) Total consideration in cash 85,000 13,027 ​ ​ 4. ACQUISITION AND DISPOSAL OF SUBSIDIARIES (CONTINUED) Acquisitions in 2019 ​ BJ Shuhai On January 2, 2019, the Company through its subsidiary, 21Vianet Beijing acquired 100% equity interests in BJ Shuhai at a total cash consideration of RMB 98,255 in installment upon achievement of certain conditions which is accounted as contingent consideration and the corresponding asset will only be recognized when the contingency is resolved. The purpose is to establish a new data center with the acquired property. As BJ Shuhai does not possess all the elements that are necessary to conduct normal operations as a business and had not yet commenced operations, such acquisition is accounted for as an acquisition of assets. As of December 31, 2020, the condition of the last payment of the total consideration was not yet met. RMB 30,000 in relation to the last payment was considered as a contingent consideration. The carrying amounts of the net identifiable assets of BJ Shuhai were as follows: ​ ​ ​ ​ ​ RMB Net assets acquired: Operating permits (Note 9) 100,380 Cash and cash equivalents 59 Other current assets 9,625 Right-of-use assets 129,937 Other current liabilities (16,714) Lease liabilities (129,937) Deferred tax liabilities (25,095) Total consideration in cash 68,255 ​ Shihua Holdings 2 In March 2017, the Company and Warburg Pincus set up a joint venture, Shihua Holdings 2, with the equity interest of 49% and 51%, respectively (Note 12). The Company accounted for the investment in the joint venture under equity method investments for its ability to exercise significant influence. In July 2019, the Company entered into restructuring agreements with Warburg Pincus and the transaction. Pursuant to the restructuring agreement, Shihua Holdings 2 transferred 100% of the equity interest in some subsidiaries at the consideration equivalent to the subsidiaries’ paid-in capital to Warburg Pincus’s wholly owned subsidiaries, Marble SH and Marble Holdings. Thereafter, Shihua Holdings 2 repurchased and cancelled all Warburg Pincus’s shares in Shihua Holdings 2. Upon completion of restructuring on August 20, 2019, the Company became the sole shareholder in Shihua Holdings 2, including its wholly owned subsidiary, Hongming Logistics. As Shihua Holdings 2 and its subsidiaries do not possess all the elements that are necessary to conduct normal operations as a business and had not yet commenced operations, such acquisition is accounted for as an acquisition of assets. The carrying amounts of the net identifiable assets of Shihua Holdings 2 at the acquisition date were as follows: ​ ​ ​ ​ ​ RMB Net assets acquired: Property and land use right 150,880 Construction-in-progress 465 Cash and cash equivalents 67,563 Other current assets 1,333,329 Other current liabilities (1,203,894) Deferred tax liabilities (33,096) Total consideration* 315,247 ​ * Consideration transferred is the carrying amount of the previously held 49% of equity interest. 4. ACQUISITION AND DISPOSAL OF SUBSIDIARIES (CONTINUED) Acquisition in 2019 (continued) NT Chenghong On December 24, 2019, the Company through its subsidiary, 21Vianet Beijing acquired 100% equity interests in NT Chenghong with total cash consideration of RMB80,000. The purpose of this transaction for the Company is to acquire the property to establish a new data center. As NT Chenghong does not possess all the elements that are necessary to conduct normal operations as a business and had not yet commenced operations, such acquisition is accounted for as an acquisition of assets. The carrying amounts of the net identifiable assets of NT Chenghong at the acquisition date were as follows: ​ ​ ​ ​ ​ RMB Net assets acquired: Construction-in-progress 158,471 Equipment 13 Cash and cash equivalents 129 Other current assets 11,840 Other current liabilities (88,830) Deferred tax liabilities (1,623) Total consideration in cash 80,000 ​ ​

ACCOUNTS AND NOTES RECEIVABLE,

ACCOUNTS AND NOTES RECEIVABLE, NET	12 Months Ended
	Dec. 31, 2020
ACCOUNTS AND NOTES RECEIVABLE, NET
ACCOUNTS AND NOTES RECEIVABLE, NET	5. ACCOUNTS AND NOTES RECEIVABLE, NET Accounts and notes receivable and the allowance for doubtful debt consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Accounts receivable 722,840 913,902 140,062 Notes receivable 2,146 2,252 345 Allowance for doubtful debt (67,828) (68,921) (10,563) ​ 657,158 847,233 129,844 ​ As of December 31, 2019 and 2020, all accounts and notes receivable were due from third party customers. An analysis of the allowance for doubtful debt was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Balance at beginning of the year 70,970 67,828 10,395 Cumulative adjustment for changes in accounting policy ​ — ​ 2,740 ​ 420 Additional provision charged to expense 485 2,393 367 Write-off of accounts receivable (3,627) (4,040) (619) Balance at the end of the year 67,828 68,921 10,563 ​

SHORT-TERM INVESTMENTS

SHORT-TERM INVESTMENTS	12 Months Ended
	Dec. 31, 2020
SHORT-TERM INVESTMENTS
SHORT-TERM INVESTMENTS	6. SHORT-TERM INVESTMENTS Short-term investments consisted of the following as of December 31, 2019 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Time deposits 363,856 285,872 43,812 ​ The Company recorded interest income related to its short-term investments amounting to RMB7,303, RMB8,687 and RMB5,712 (US$875) for the years ended December 31, 2018, 2019 and 2020, respectively, in the consolidated statements of operations.

PREPAID EXPENSES AND OTHER CURR

PREPAID EXPENSES AND OTHER CURRENT ASSETS	12 Months Ended
	Dec. 31, 2020
PREPAID EXPENSES AND OTHER CURRENT ASSETS
PREPAID EXPENSES AND OTHER CURRENT ASSETS	7. PREPAID EXPENSES AND OTHER CURRENT ASSETS Prepaid expenses and other current assets consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Prepaid expenses 878,155 884,156 135,503 Tax recoverables ​ 570,913 ​ 879,237 ​ 134,749 Deposits 17,391 31,774 4,870 Loan to third parties 73,557 19,107 2,928 Interest receivables 14,359 1,484 227 Staff advances 1,866 968 148 Others 61,908 49,458 7,580 ​ 1,618,149 1,866,184 286,005 ​ Prepaid expenses mainly represented the unamortized portion of prepayments made to Microsoft for the cloud computing services, the prepayments to telecommunication operators for bandwidth, data centers or cabinets and the prepayments for office expense.

PROPERTY AND EQUIPMENT, NET

PROPERTY AND EQUIPMENT, NET	12 Months Ended
	Dec. 31, 2020
PROPERTY AND EQUIPMENT, NET
PROPERTY AND EQUIPMENT, NET	8. PROPERTY AND EQUIPMENT, NET Property and equipment, including those held under finance leases, consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ At cost: ​ ​ ​ ​ ​ ​ Property 899,609 1,511,429 231,637 Leasehold improvements 1,458,749 2,609,828 399,974 Computer and network equipment 3,539,709 4,899,577 750,893 Optical fibers 142,723 142,723 21,873 Office equipment 22,102 26,845 4,114 Motor vehicles 2,308 2,668 409 ​ 6,065,200 9,193,070 1,408,900 Less: Accumulated depreciation (2,514,800) (3,285,138) (503,469) Impairment ​ — ​ (35,793) ​ (5,486) ​ 3,550,400 5,872,139 899,945 Construction-in-progress 1,893,165 2,234,286 342,419 ​ 5,443,565 8,106,425 1,242,364 ​ 8. PROPERTY AND EQUIPMENT, NET (CONTINUED) Depreciation expense was RMB566,491, RMB696,528 and RMB908,387 (US$139,216) for the years ended December 31, 2018, 2019 and 2020, respectively, and were included in the following captions: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Cost of revenues 520,791 644,108 850,746 130,382 Sales and marketing expenses 986 2,107 2,399 368 General and administrative expenses 28,727 30,110 29,711 4,553 Research and development expenses 15,987 20,203 25,531 3,913 ​ 566,491 696,528 908,387 139,216 ​ The carrying amounts of the Company’s property and equipment held under finance leases at respective balance sheet dates were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Property 365,353 921,970 141,298 Computer and network equipment 639,311 1,019,588 156,259 Optical fibers 142,723 137,924 21,138 ​ 1,147,387 2,079,482 318,695 Less: Accumulated depreciation (408,196) (661,796) (101,425) ​ 739,191 1,417,686 217,270 Construction-in-progress 659,014 92,545 14,183 ​ 1,398,205 1,510,231 231,453 ​ Depreciation of property, computer and network equipment and optical fibers under finance leases was RMB170,264, RMB216,664 and RMB255,458 (US$39,151) for the years ended December 31, 2018, 2019 and 2020, respectively. The carrying amounts of property and equipment pledged by the Company to secure borrowings (Note 13) granted to the Company at the respective balance sheet dates were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Property 137,585 264,784 40,580 Leasehold improvements ​ 66,162 ​ 90,947 ​ 13,938 Computer and network equipment ​ — ​ 40,871 ​ 6,264 Construction-in-progress — 238,771 36,593 ​

INTANGIBLE ASSETS, NET

INTANGIBLE ASSETS, NET	12 Months Ended
	Dec. 31, 2020
INTANGIBLE ASSETS, NET
INTANGIBLE ASSETS, NET	9. INTANGIBLE ASSETS, NET The following table presented the Company’s intangible assets as of the respective balance sheet dates: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Radio ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Internal ​ ​ ​ ​ Purchased ​ spectrum ​ Operating ​ Contract ​ Customer ​ ​ ​ Supplier ​ Trade ​ Customer ​ Non-compete ​ use ​ ​ ​ ​ software ​ license ​ Permits ​ backlog ​ relationships ​ Licenses ​ relationships ​ names ​ contract ​ agreements ​ software ​ Total ​ RMB RMB RMB RMB RMB RMB RMB RMB RMB RMB RMB RMB Intangible assets, net January 1, 2019 47,254 72,908 — 5,162 112,961 3,883 17,070 90,591 — 44 5,440 355,313 Additions 11,128 — 100,380 — — — — — — — 13,189 124,697 Foreign currency translation difference 413 1,200 — — — — — — — — — 1,613 Amortization expense (16,068) (8,985) (3,136) (5,162) (24,921) (385) (3,074) (5,813) — (44) (3,440) (71,028) Intangible assets, net December 31, 2019 42,727 65,123 97,244 — 88,040 3,498 13,996 84,778 — — 15,189 410,595 Additions 12,893 ​ — 274,904 — — — — — 66,708 — 8,684 363,189 Foreign currency translation difference (32) (4,213) — — — — — — — — — (4,245) Amortization expense (13,689) (8,403) (5,189) — (24,854) (385) (3,074) (5,813) (3,602) — (7,681) (72,690) Impairment ​ — ​ (38,654) ​ — ​ — ​ — ​ — ​ — ​ — ​ — ​ — ​ — ​ (38,654) Intangible assets, net December 31, 2020 41,899 13,853 366,959 — 63,186 3,113 10,922 78,965 63,106 — 16,192 658,195 Intangible assets, net December 31, 2020 (US$) 6,421 2,123 56,239 — 9,684 477 1,674 12,102 9,671 — 2,482 100,873 ​ Contract backlog relate to the order placed by the customers that have yet to be delivered at the acquisition date. Customer relationships relate to the relationships that arose as a result of existing customer agreements acquired and is derived from the estimated net cash flows that are expected to be derived from the expected renewal of these existing customer agreements after subtracting the estimated net cash flows from other contributory assets. Customer contract related to existing customer agreements acquired and is derived from the estimated net cash flows that are expected to be derived over the contractual period of the existing customer agreements after subtracting the estimated net cash flows from other contributory assets. Licenses mainly represented the telecommunication service license in relation to virtual private network services. Supplier relationships relate to the relationships that arose as a result of existing bandwidth supply agreements with certain network operators, which were valued using a replacement cost method given the relative ease of replacement. Trade names mainly relate to the trade names of Dermot Entities. Operating permits relate to the government authorized high-capacity utilities from the assets acquisitions (Note 4). The intangible assets are amortized using the straight-line method, which is the Company’s best estimate of how these assets will be economically consumed over their respective estimated useful lives ranging from 1 to 36 years. Amortization expenses were approximately RMB68,115, RMB71,028 and RMB72,690 (US$11,140) for the years ended December 31, 2018, 2019 and 2020, respectively. The annual estimated amortization expenses for the intangible assets for each of the next five years are as follows: ​ ​ ​ ​ ​ ​ ​ RMB US$ 2021 78,149 11,977 2022 63,039 9,661 2023 41,574 6,371 2024 31,923 4,892 2025 27,424 4,203 ​ 242,109 37,104 ​

LAND USE RIGHTS, NET

LAND USE RIGHTS, NET	12 Months Ended
	Dec. 31, 2020
LAND USE RIGHTS, NET
LAND USE RIGHTS, NET	10. LAND USE RIGHTS, NET Land use rights held by the Company represent operating lease prepayments and are amortized over the remaining term of the respective rights. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Cost 249,804 278,138 42,627 Accumulated amortization (16,650) (22,765) (3,489) Land use rights, net 233,154 255,373 39,138 ​ The carrying amounts of land use rights pledged by the Company to secure borrowings (Note 13) granted to the Company at the respective balance sheet dates were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Land use rights 15,989 141,000 21,609 ​

GOODWILL

GOODWILL	12 Months Ended
	Dec. 31, 2020
GOODWILL
GOODWILL	11. GOODWILL The changes in the carrying amount of goodwill were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Balance as of January 1 989,530 989,530 151,652 Additions ​ — ​ 5,463 ​ 837 Balance as of December 31 989,530 994,993 152,489 ​ As of December 31, 2018, 2019 and 2020, the Company has performed a qualitative assessment for hosting and related services and no impairment loss was recorded.

LONG-TERM INVESTMENTS, NET

LONG-TERM INVESTMENTS, NET	12 Months Ended
	Dec. 31, 2020
LONG-TERM INVESTMENTS, NET
LONG-TERM INVESTMENTS, NET	12. LONG-TERM INVESTMENTS, NET The Company’s long-term investments consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Equity investments without readily determinable fair values 43,824 17,137 2,626 Equity method investments 124,116 116,667 17,880 Available-for-sale debt investments 1,713 1,713 263 ​ 169,653 135,517 20,769 ​ Equity investments without readily determinable fair values The Company disposed equity investments without readily determinable fair value at a consideration of RMB13,122 and RMB13,500 (US$2,069) in 2019 and 2020, respectively. The investment income comprised of dividend income of RMB406, RMB461 and RMB607 (US$93), and disposal gain of RMB20,496, RMB5,536 and RMB257 (US$39) for the years ended December 31, 2018, 2019 and 2020, respectively. ​ 12. LONG-TERM INVESTMENTS, NET (CONTINUED) Equity investments without readily determinable fair values (continued) The Company recorded an impairment loss of long-term investment amounting nil, nil and RMB13,030 (US$1,997) for the years ended December 31, 2018, 2019 and 2020, respectively. Equity method investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Increase (decrease) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ during ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the year ended ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2018 ​ December 31, 2019 ​ As of December 31, 2019 ​ ​ ​ ​ Share ​ Investments ​ ​ ​ Share ​ Distribution/derecognize ​ ​ ​ Share ​ Investments ​ ​ Cost of ​ equity ​ in equity ​ Cost of ​ equity gain ​ of share ​ Cost of ​ equity gain ​ in equity ​ investments gain (loss) investee investments (loss) equity (gain) loss investments (loss) investee ​ RMB RMB ​ RMB RMB RMB ​ RMB RMB RMB ​ RMB Yizhuang Fund 101,000 25,681 ​ 126,681 — ​ 1,671 ​ (20,200) ​ 101,000 ​ 7,152 ​ 108,152 Shihua DC Holdings 366,623 (33,658) ​ 332,965 (337,555) ​ (17,718) ​ 22,308 ​ 29,068 ​ (29,068) ​ — Jingliang Inter Cloud ​ 6,000 (34) ​ 5,966 — ​ (1,894) ​ — ​ 6,000 ​ (1,928) ​ 4,072 Jingliang Century Cloud ​ 4,000 — ​ 4,000 — ​ — ​ — ​ 4,000 ​ — ​ 4,000 Huaye Cloud ​ 23,333 (6,319) ​ 17,014 (23,333) ​ (11,534) ​ 17,853 ​ — ​ — ​ — ZJK Energy ​ 5,907 (2,157) ​ 3,750 — ​ 212 ​ — ​ 5,907 ​ (1,945) ​ 3,962 WiFire Entities 15,000 (15,000) ​ — 5,000 ​ (5,000) ​ — ​ 20,000 ​ (20,000) ​ — Qidi Chengxin ​ — ​ — ​ — ​ 3,930 ​ — ​ — ​ 3,930 ​ — ​ 3,930 ​ 521,863 (31,487) ​ 490,376 (351,958) ​ (34,263) ​ 19,961 ​ 169,905 ​ (45,789) ​ 124,116 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Increase (decrease) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ during ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the year ended ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2019 ​ December 31, 2020 ​ As of December 31, 2020 ​ ​ ​ ​ Share ​ Investments ​ ​ ​ Share ​ Distribution/derecognize ​ ​ ​ Share ​ Investments ​ Investments ​ ​ Cost of ​ equity ​ in equity ​ Cost of ​ equity gain ​ of share ​ Cost of ​ equity gain ​ in equity ​ in equity ​ investments gain (loss) investee investments (loss) equity (gain) loss investments (loss) investee investee ​ RMB RMB ​ RMB ​ RMB ​ RMB ​ RMB ​ RMB ​ RMB ​ RMB ​ US$ Yizhuang Fund 101,000 ​ 7,152 ​ 108,152 ​ — ​ 12,254 ​ (17,723) ​ 101,000 ​ 1,683 ​ 102,683 ​ 15,737 Shihua DC Holdings 29,068 ​ (29,068) ​ — ​ (29,068) ​ — ​ 29,068 ​ — ​ — ​ — ​ — Jingliang Inter Cloud 6,000 ​ (1,928) ​ 4,072 ​ — ​ (903) ​ — ​ 6,000 ​ (2,831) ​ 3,169 ​ 486 Jingliang Century Cloud 4,000 ​ — ​ 4,000 ​ — ​ — ​ — ​ 4,000 ​ — ​ 4,000 ​ 613 ZJK Energy 5,907 ​ (1,945) ​ 3,962 ​ — ​ (803) ​ — ​ 5,907 ​ (2,748) ​ 3,159 ​ 484 WiFire Entities 20,000 ​ (20,000) ​ — ​ — ​ — ​ — ​ 20,000 ​ (20,000) ​ — ​ — Qidi Chengxin ​ 3,930 ​ — ​ 3,930 ​ — ​ (274) ​ — ​ 3,930 ​ (274) ​ 3,656 ​ 560 ​ 169,905 ​ (45,789) ​ 124,116 ​ (29,068) ​ 10,274 ​ 11,345 ​ 140,837 ​ (24,170) ​ 116,667 ​ 17,880 ​ ​ 12. LONG-TERM INVESTMENTS, NET (CONTINUED) Equity method investments (continued): The Company through its subsidiary, 21Vianet Beijing, entered into an agreement to invest in the Yizhuang Venture Investment Fund (“Yizhuang Fund”) as a limited partner since April 2012 with capital injection of RMB101,000 and held 27.694% of the investee as of December 31, 2018, 2019 and 2020. Given the Company holds more than three percent interest in the Yizhuang Fund as a limited partner, the investment is accounted for under the equity method as prescribed in ASC Subtopic 323-10, Investments – Equity Method In March 2017, the Company through its subsidiary, 21Vianet HK, and Warburg Pincus jointly set up two JVs, Shihua Holdings 2 and Shihua Investment Management (collectively, “Shihua DC Holdings”). The Company injected capital of RMB133,639 and RMB13,537 to acquire 49% of equity interest in Shihua Holdings 2 and Shihua In September 2017, after the disposal of 66.67% equity interest in the WiFire Entities, the Company held the remaining 33.33% equity interest in the WiFire Entities, which is accounted for equity method investment at fair value at the disposal date. In 2019, the Company increased capital injection of RMB5,000 in the WiFire Entities. As of December 31, 2020, the equity method investment balance is reduced to nil after the pickup of loss in the WiFire Entities. In January 2018, the Company through its subsidiary, 21Vianet Beijing, and a third company jointly set up Beijing Jingliang Interconnected Cloud Technology Inc. (“Jingliang Inter Cloud”) and Jingliang Century Cloud Technology Inc. (“Jingliang Century Cloud”). The Company injected capital of RMB6,000 and RMB4,000 and the Company held 60% and 40% of equity interest in Jingliang Inter Cloud and Jingliang Century Cloud, respectively. Based on the article of association, the Company cannot exercise control over relevant activities of the investee, but it has the ability to exercise significant influence over Jingliang Inter Cloud’s operation and financial decisions. In March 2018, the Company through its subsidiary, 21Vianet Beijing, acquired 50% equity interest in Guangdong Huaye Cloud Inc. (“Huaye Cloud”) with an amount of RMB23,333, with the ability to exercise significant influence. In November 2019, the Company disposed all its equity interest in Huaye Cloud with a total cash consideration of RMB23,333 and recognized investment loss with an amount of RMB17,853 and disposal gain with an amount of RMB17,853. In December 2019, the Company through its subsidiary, 21Vianet Beijing, and a third company jointly set up Chengdu Qidi Chengxin Education Limit (“Qidi Chengxin”). The Company injected capital of RMB3,930 and hold 59% of equity interest in Qidi Chengxin. Based on the article of association, the Company cannot exercise control over relevant activities of the investee, but it has the ability to exercise significant influence over operation and financial decisions.

BORROWINGS

BORROWINGS	12 Months Ended
	Dec. 31, 2020
BORROWINGS
BORROWINGS	13. BORROWINGS Borrowings were as follows as of the respective balance sheet dates: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Short-term bank borrowings 234,500 34,000 5,211 Long-term bank borrowings, current portion 32,500 68,500 10,498 Other long-term borrowings, current portion ​ — ​ 111,828 ​ 17,138 ​ 267,000 214,328 32,847 Long-term bank borrowings, non-current portion 79,500 605,119 92,738 Other long-term borrowings, non-current portion ​ — ​ 281,877 ​ 43,200 Total borrowings 346,500 1,101,324 168,785 ​ The short-term borrowings outstanding as of December 31, 2019 and 2020 bore a weighted average interest rate of 4.56% and 4.46% per annum, respectively, and were denominated in RMB. These borrowings were obtained from financial institutions and have terms of one year. The long-term borrowings (including current portion) outstanding as of December 31, 2019 and 2020 bore a weighted average interest rate of 5.28% and 5.61% per annum, respectively, and were denominated in RMB. These loans were obtained from financial institutions located in the PRC. As of December 31, 2019 and 2020, unused loan facilities for bank and other borrowings amounted to RMB326,068 and RMB1,574,556 (US$241,311), respectively. Borrowings as of December 31, 2019 and 2020 were secured by the following: ​ December 31, 2019 ​ ​ ​ ​ Short-term bank borrowings Secured by (RMB) 34,500 ​ Unsecured borrowings. ​ ​ ​ 200,000 ​ Secured by restricted cash of RMB215,816. 234,500 ​ ​ ​ ​ ​ Long-term bank borrowings (including current portion) Secured by (RMB) 112,000 Secured by a subsidiary’s fixed assets and land-use right with net book value of RMB203,747 and RMB15,989, respectively (Note 8/Note 10). 112,000 ​ ​ ​ 13. BORROWINGS (CONTINUED) December 31, 2020 ​ ​ ​ Short-term bank borrowings Secured by (RMB) 34,000 ​ Unsecured borrowings. ​ ​ ​ 34,000 ​ ​ ​ ​ ​ Long-term borrowings (including current portion) Secured by (RMB) 404,781 Secured by subsidiary’s property and equipment and land-use right with net book value of RMB505,004 (US$77,395) and RMB40,034 (US$6,135), respectively (Note 8/Note 10). 271,861 ​ Secured by a subsidiary’s property and equipment and land-use right with net book value of RMB130,369 (US$19,980) and RMB100,966 (US$15,474), respectively (Note 8/Note 10), and a subsidiary’s stock. 190,682 ​ Unsecured borrowing. 100,000 ​ Secured by a subsidiary’s stock and the restricted cash of RMB104,400 (US$16,000). 100,000 Secured by a subsidiary’s stock. 1,067,324 ​ ​ ​

ACCRUED EXPENSES AND OTHER PAYA

ACCRUED EXPENSES AND OTHER PAYABLES	12 Months Ended
	Dec. 31, 2020
ACCRUED EXPENSES AND OTHER PAYABLES
ACCRUED EXPENSES AND OTHER PAYABLES	14. ACCRUED EXPENSES AND OTHER PAYABLES The components of accrued expenses and other payables were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Payables for purchase of property, equipment and software 554,693 1,148,742 176,052 Payroll and welfare payables 179,195 204,732 31,377 Amounts due to the original shareholders for acquired entities * — 66,466 10,186 Payables for acquisitions 47,805 47,805 7,326 Accrued service fees 52,746 47,572 7,291 Payables for office supplies and utilities 24,562 38,485 5,898 Interest payables 58,961 37,799 5,793 Value-added tax and other taxes payable 14,523 10,473 1,605 Others 46,450 29,489 4,520 ​ 978,935 1,631,563 250,048 ​ * This represented the balance of unpaid cash consideration and the payables in other current liabilities due to original shareholders related to the acquisition of SH Shuzhong and LF Huahai (Note 4).

LEASES

LEASES	12 Months Ended
	Dec. 31, 2020
LEASES
LEASES	15. LEASES Leases are classified as operating leases or finance leases in accordance with ASC 842. The Company’s operating leases mainly related to building, office facilities and equipment and the rights to use the land in the PRC. For leases with terms greater than 12 months, the Company records the related asset and liability at the present value of lease payments over the term. Certain leases include rental escalation clauses, renewal options and/or termination options, which are factored into the Company’s determination of lease payments when appropriate. ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2019 2020 Weighted average remaining lease term: ​ ​ ​ ​ ​ Operating lease 9.4 years 12.2 years ​ Finance lease 15.3 years 14.6 years ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate: ​ Operating lease 6.09 % 6.56 % Finance lease 8.43 % 8.63 % ​ Lease cost for finance leases capitalized were immaterial for the years ended December 31, 2019 and 2020. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Lease cost Finance lease cost: Depreciation 216,664 255,458 39,151 Interest expenses 120,185 130,196 19,953 Operating lease cost 214,795 478,805 73,380 Total lease cost 551,644 864,459 132,484 ​ Short-term lease cost and variable lease cost for operating leases and finance leases were immaterial for the years ended December 31, 2019 and 2020. Other information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ ​ Operating cash payments for operating leases 193,174 477,189 73,132 Financing cash payments for finance leases 333,614 376,232 57,660 ​ ​ 15. LEASES (CONTINUED) Future lease payments under operating leases and finance leases as of December 31, 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases ​ Finance Leases ​ RMB US$ RMB US$ 2021 415,892 ​ 63,738 ​ 542,268 83,106 2022 221,680 ​ 33,974 ​ 293,643 45,003 2023 146,115 ​ 22,393 ​ 195,320 29,934 2024 103,891 ​ 15,922 ​ 124,389 19,063 2025 ​ 70,494 ​ 10,804 ​ 95,054 ​ 14,568 2026 and thereafter 1,115,382 ​ 170,940 ​ 1,678,170 257,191 Total future lease payments 2,073,454 ​ 317,771 ​ 2,928,844 448,865 Less: Imputed interest (728,543) ​ (111,654) ​ (1,286,619) (197,183) Present value of future lease payments * 1,344,911 ​ 206,117 ​ 1,642,225 251,682 ​ * Present value of future operating lease payments consisted of current portion of operating lease liabilities, non-current portion of operating lease liabilities and operating lease liabilities in amounts due to related parties, amounting to RMB452,272 (US$69,314), RMB645,499 (US$98,927) and RMB247,140 (US$37,876) for the year ended December 31, 2020, respectively. Present value of future finance lease payments consisted of current portion of finance lease liabilities, non-current portion of finance lease liabilities and finance lease liabilities in amounts due to related parties, amounting to RMB403,843 (US$61,892), RMB688,128 (US$105,460) and RMB550,254 (US$84,330) for the year ended December 31, 2020, respectively.

BONDS PAYABLE

BONDS PAYABLE	12 Months Ended
	Dec. 31, 2020
BONDS PAYABLE
BONDS PAYABLE	16. BONDS PAYABLE On April 15, 2019, the Company issued and sold bonds with an aggregate principle amount of US$300,000 at a coupon rate of 7.875% per annum (“2021 Notes”). The 2021 Notes will mature on October 15, 2021. The 2021 Notes were listed and quoted on the SGX-ST. Interest on the 2021 Notes is payable semi-annually in arrears on April 15 and October 15 in each year, beginning from October 15, 2019. Net proceeds from 2021 Notes after deducting issuance costs were RMB1,976,474. The 2021 Notes are unsecured and rank senior in right of payment to any of the Company’s indebtedness that is expressly subordinated to the bonds; equal in right of payment to any of the Company’s liabilities that are not so subordinated, including the 2020 Notes; effectively junior in the right of payment to any secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness and other liabilities (including accounts payables) of the Company’s subsidiaries and Consolidated VIEs. On April 16, 2019, the Company repurchased US$150,839 in principal amount of 2020 Notes, representing approximately 50.28% of the US$300,000 total aggregate principal amount of the 2020 Notes outstanding as at such date. On August 12, 2019, the Company repurchased US$18,000 in principal amount of 2020 Notes. The remaining outstanding 2020 Notes with principal amount of US$131,161 continue to be the obligation of the Company. The Company recognized loss on debt extinguishment of RMB18,895 during the year ended December 31, 2019. On August 4, 2020, the Company repaid the remaining outstanding 2020 Notes with principal amount of US$131,161. The following table summarizes the aggregate required repayments of the principal amounts of the Company’s long-term borrowings, including the bonds payable, bank and other borrowings (Note 13) in the succeeding five years and thereafter: ​ ​ ​ ​ ​ ​ ​ RMB US$ For the years ending December 31, ​ ​ ​ ​ 2021 2,158,266 ​ 330,769 2022 222,796 ​ 34,145 2023 152,544 ​ 23,378 2024 189,988 ​ 29,117 2025 ​ 125,244 ​ 19,194 2026 and thereafter 222,119 ​ 34,041 ​

PERPETUAL CONVERTIBLE PREFERRED

PERPETUAL CONVERTIBLE PREFERRED SHARES	12 Months Ended
	Dec. 31, 2020
PERPETUAL CONVERTIBLE PREFERRED SHARES
PERPETUAL CONVERTIBLE PREFERRED SHARES	17. PERPETUAL CONVERTIBLE PREFERRED SHARES In June 2020, the Company issued 150,000 Series A perpetual convertible preferred shares (the “Series A Preferred Shares”) at the subscription price of 1,000 US dollars per subscribed share for a total cash consideration of US$150,000. The significant terms of the Series A Preferred Shares are summarized as follows: Dividends From and after the original issuance date, cumulative dividends on each Series A Preferred Share will accrue in arrears at the dividend rate of 4.5% per annum on the original issuance price of US$1,000 per subscribed share. All accrued dividends on any Series A Preferred Share will be paid in cash, when, as and if declared by the Board of Directors out of funds legally available therefor or upon a liquidation of the Company. Holders of the Series A Preferred Shares will also be entitled to receive any dividends declared by the Board of Directors on a pro rata basis with the ordinary shares determined on an as-converted basis. The dividends or distributions shall be distributed among all holders of ordinary shares and Series A Preferred Shares in proportion to the number of ordinary shares that would be held by each such holder if all Series A Preferred Shares had been converted to ordinary shares as of the record date fixed for determining those entitled to receive such distribution. For dividends on cumulative preferred stock classified in permanent equity, dividends are not recognized until declared by the Board of Directors. As of December 31,2020, no dividend was declared by the Company and the cumulative dividend was RMB22,806 (US$3,495). Liquidation preference In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company, the holders of Series A Preferred Shares will be entitled to be paid out of the assets of the Company available for distribution to its shareholders before any distribution or payment out of the assets of the Company will be made to the holders of ordinary shares at a preferential amount in cash equal to the greater of (i) the aggregate original issuance price of US$1,000 per Series A Preferred Shares, plus any unpaid, accrued and accumulated dividends on all such Series A Preferred Shares (whether or not declared) and (ii) the aggregate value that such holders of Series A Preferred Shares would have received had all holders of Series A Preferred Shares, immediately prior to such Liquidation, converted all Series A Preferred Shares then outstanding (together with any unpaid, accrued and accumulated dividends thereon) into Class A ordinary shares at the applicable conversion price then in effect. If the Company has insufficient assets to pay the holders of the Series A Preferred Shares the full preferential amount, (a) the holders of the Series A Preferred Shares will share ratably in any distribution of the remaining assets of the Company in proportion to the respective full preferential amounts which would otherwise be payable to each such holder in full, and (b) the Company will not make or agree to make, or set aside for the benefit of the holders of ordinary shares, any payments to the holders of ordinary shares. ​ 17. PERPETUAL CONVERTIBLE PREFERRED SHARES (CONTINUED) Conversion Series A Preferred Shares can be converted at any time at the option of the holder into Class A ordinary shares by dividing the original issuance price plus any unpaid, accrued and accumulated dividends up to, but excluding, the conversion date by the conversion price in effect immediately prior to such conversion. Series A Preferred Shares will be mandatorily converted into Class A ordinary shares at any time after six months from the original issuance date when the daily volume-weighted average price of the ADS (“VWAP”) of certain period equals or exceeds the 200% of the conversion price per ADS (“Conversion Threshold”). Conversion price is initially, US$2.8333 per Class A Ordinary Shares or US$17.00 per ADS and is subject to additional adjustments if the Company makes certain dilutive issuances of shares. Voting Each Series A Preferred Shares holder will be entitled to a number of vote equal to the number of Class A ordinary shares then issuable upon its conversion into Class A ordinary shares at the record date for determination of the shareholders entitled to vote on such matters, or, if no such record date is established, at the date when such vote is taken or any written consent of shareholders is solicited. Accounting for the Series A Preferred Shares The Series A Preferred Shares are classified as permanent equity and initially recorded at the issuance price at the time of closing. There were no embedded features that qualified for bifurcation and separate accounting in accordance with ASC 815-10, Derivatives and Hedging. As the time of closing, beneficial conversion features with the amount of RMB470,643 (US$72,129) was recorded as a reduction to the respective preferred shares with an offsetting credit to additional paid-in capital. This amount was immediately accreted back as a deemed distribution to Series A perpetual convertible preferred shareholders.

CONVERTIBLE PROMISSORY NOTES

CONVERTIBLE PROMISSORY NOTES	12 Months Ended
	Dec. 31, 2020
CONVERTIBLE PROMISSORY NOTES
Disclosure Of Convertible Promissory Notes [Text Block]	18. CONVERTIBLE PROMISSORY NOTES During the year ended December 31, 2020, a group of investors led by Goldman Sachs Asia Strategic Pte. Ltd. (the “Purchasers”) subscribed and paid cash consideration of US$200,000 in aggregate for the Company’s convertible promissory notes (the “Notes”). The Notes will mature in five years and, bear interest at the rate of 2% per annum from the issuance date which will be payable semiannually in arrears in cash. Conversion Purchasers have the option to convert all or a portion of the outstanding Notes and any accrued and unpaid interest, into ADSs at the conversion price at any time. The conversion price will initially be US$12.00 per ADS or will be subject to customary adjustments when the decrease in VWAP exceeds certain threshold. In addition, the conversion price will be adjusted in the event when the Company makes certain dilutive issuances of shares. Redemption upon maturity Unless previously redeemed or converted, the Company shall redeem the Notes on the maturity date in an amount equal to the sum of (i) 115% of the then outstanding principal amount of the Notes and (ii) the interest accrued but unpaid on the maturity date. The Company may not redeem the Notes at its option prior to the maturity date. Early redemption at the option of the Purchasers If any portion of the outstanding principal amount of the Notes has not been converted by the third anniversary of the date of issuance of the Notes, the Purchasers at their sole discretion will have the right to require the Company to redeem, in whole or in part, the outstanding principal amount of the Notes which has not been converted previously in an amount equal to the sum of (i) 109% of the outstanding principal amount and (ii) the interest accrued but unpaid on the outstanding principal amount. The Company elected to account for the Notes at fair value as a whole. Issuance costs including underwriting commissions and offering expenses were approximately RMB18,932 (US$2,901), which were recognized in earnings as incurred. In August and December 2020, Purchasers of the Notes exercised the right to convert 12,499,998 and 11,210,142 newly issued Class A ordinary shares at the conversion price of US$12 per ADS. Upon conversion, the fair value of converted portion was RMB720,547 (US$110,429) and issuance costs were approximately RMB2,939 (US$450), which were credited to capital accounts with the changes in the fair value up to the conversion date recorded in earning. The interest expense on the convertible promissory was recorded based on the stated rate of 2% in the interest expense within the consolidated statements of operations. The Company elected the fair value option in accordance with ASC 825 to subsequently remeasure the Notes. As of December 31, 2020, the fair value of the Notes was RMB3,014,057 (US$461,924), and the changes in fair value of convertible promissory notes of RMB2,544,220 (US$389,919) was recognized in the changes in the fair value of convertible promissory notes in the consolidated statement of operations for the year ended December 31, 2020. The fair value changes related to instrument-specific credit risk is nil for the year ended December 31, 2020.

DEFERRED GOVERNMENT GRANTS

DEFERRED GOVERNMENT GRANTS	12 Months Ended
	Dec. 31, 2020
DEFERRED GOVERNMENT GRANTS
DEFERRED GOVERNMENT GRANTS	19. DEFERRED GOVERNMENT GRANTS During the years ended December 31, 2018, 2019 and 2020, the Company received RMB500, nil and nil, respectively, in government grants from the relevant PRC government authorities for the use in construction of property and equipment. These grants are initially deferred and subsequently recognized in the consolidated statements of operations when the Company has complied with the conditions or performance obligations attached to the related government grants, if any, and the grants are no longer refundable. Grants that subsidize the construction cost of property and equipment are amortized over the life of the related assets as a reduction of the associated depreciation expense. Movements of deferred government grants were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Balance at beginning of the year 22,435 15,792 8,501 1,303 Additions 500 — — — Recognized as a reduction of depreciation expense (7,143) (7,291) (2,327) (357) Balance at end of the year 15,792 8,501 6,174 946 ​

TREASURY STOCK

TREASURY STOCK	12 Months Ended
	Dec. 31, 2020
TREASURY STOCK
TREASURY STOCK	20. TREASURY STOCK For the years ended December 31, 2018, 2019 and 2020, the Company repurchased the number of nil, 242,830 and nil ADSs pursuant to the share repurchase plans.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME	12 Months Ended
	Dec. 31, 2020
ACCUMULATED OTHER COMPREHENSIVE INCOME
ACCUMULATED OTHER COMPREHENSIVE INCOME	21. ACCUMULATED OTHER COMPREHENSIVE INCOME The changes in accumulated other comprehensive income by component, net of tax of nil, were as follows: ​ ​ ​ ​ ​ ​ Foreign currency ​ ​ translation ​ RMB Balance as of January 1, 2018 (2,673) Current year other comprehensive income 88,652 Balance as of December 31, 2018 85,979 Current year other comprehensive loss (8,075) Balance as of December 31, 2019 77,904 Current year other comprehensive loss (133,439) Balance as of December 31, 2020 (55,535) Balance as of December 31, 2020, in US$ (8,511) ​

MAINLAND CHINA EMPLOYEE CONTRIB

MAINLAND CHINA EMPLOYEE CONTRIBUTION PLAN	12 Months Ended
	Dec. 31, 2020
MAINLAND CHINA EMPLOYEE CONTRIBUTION PLAN
MAINLAND CHINA EMPLOYEE CONTRIBUTION PLAN	22. MAINLAND CHINA EMPLOYEE CONTRIBUTION PLAN As stipulated by the regulations of the PRC, full-time employees of the Company in the PRC participate in a government-mandated multiemployer defined contribution plan organized by municipal and provincial governments. Under the plan, certain pension benefits, medical care, unemployment insurance, employee housing fund and other welfare benefits are provided to employees. The Company is required to make contributions to the plan based on certain percentages of employees’ salaries. The total expenses for the plan were RMB122,362, RMB121,266 and RMB77,982 (US$11,951) for the years ended December 31, 2018, 2019 and 2020, respectively.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2020
SHARE-BASED COMPENSATION
SHARE-BASED COMPENSATION	23. SHARE - Option granted to employees In order to provide additional incentives to employees and to promote the success of the Company’s business, the Company adopted a share incentive plan in 2010 (the “2010 Plan”). Under the 2010 Plan, the Company may grant options and RSUs to its employees, directors and consultants to purchase an aggregate of no more than 39,272,595 ordinary shares of the Company. The 2010 Plan was approved by the Board of Directors and shareholders of the Company on July 16, 2010. The 2010 Plan is administered by the Board of Directors or the Compensation Committee of the Board as set forth in the 2010 Plan (the “Plan Administrator”). All share options to be granted under the 2010 Plan have a contractual term of ten years and generally vest over 3 to 4 years in the grantee’s option agreement. In order to further promote the success and enhance the value, the Company adopted a share incentive plan in 2014 (the “2014 Plan”). Under the 2014 Plan, the Company may issue an aggregate of no more than 20,461,380 shares (“Maximum Number”) and such Maximum Number should be automatically increased by a number that is equal to 15% of the number of new shares issued by the Company from time to time. The maximum aggregate number of ordinary shares to be issued under 2014 Plan was subsequently amended to 39,606,817, as approved by the Board of Directors and shareholders of the Company on October 30, 2015. All share options, restricted shares and restricted share units to be granted under the 2014 Plan have a contractual term of ten years and generally vest over 3 to 4 years in the grantee’s option agreement. In order to continuously attract and retain talents, the Company adopted a share incentive plan in 2020 (the “2020 Plan”). Under the 2020 Plan, the Company is authorized to issue an aggregate of 46,560,708 Class A ordinary shares of the Company (equal to the sum of (i) 5% of the Company’s share capital as of the date hereof, calculated on an as-converted basis by taking into consideration all the convertible promissory notes issued and to be issued by the Company, and (ii) 7,562,532 Class A ordinary shares reserved under the “2010 Plan” and “2014 Plan” for future grants) will be reserved for future issuance. After adoption of the 2020 Plan, the Company will cease to grant any new awards under the 2010 Plan and 2014 Plan while the 2010 Plan and 2014 Plan and outstanding awards granted thereunder will remain effective and can be amended by the Company from time to time pursuant to the applicable terms thereto. The 2020 Plan was approved by the Board of Directors and shareholder of the Company on May 13, 2020. The Company granted 487,368, 464,120 and 314,842 RSUs in 2018, 2019 and 2020, respectively, with performance conditions whereby a predetermined number will vest upon the assignment of an annual performance review in accordance with predetermined performance targets for the grantees over a one The Company granted 2,188,226, 64,000 and 1,848,701 RSUs in 2018, 2019 and 2020, respectively, with performance conditions whereby a predetermined number will vest upon with the achievement of predetermined operation performance targets for the Company. As it is probable for the Company to estimate the operation performance for the Company, the Company recognized the related compensation expenses using the accelerated recognition method. The Company granted 547,056 , 23. SHARE BASED COMPENSATION (CONTINUED) Option granted to employees (continued) The compensation expenses related to remaining unvested share options shall be recognized over the remaining requisite service period or the performance review period. As of December 31, 2020, options to purchase 508,866 of ordinary shares were outstanding. The following table summarized the Company’s employee share option activity under the 2010 Plan: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ average ​ ​ ​ ​ ​ ​ average ​ remaining ​ Aggregate ​ ​ Number of ​ exercise ​ contractual ​ intrinsic ​ ​ options ​ price ​ term ​ value ​ ​ (US$) (Years) (US$) Outstanding, January 1, 2020 1,445,345 0.51 1.3 — Exercised (459,168) 0.69 ​ ​ Forfeited ​ (477,311) ​ 0.53 ​ ​ ​ ​ Outstanding, December 31, 2020 508,866 0.33 0.8 2,774 Vested and expected to vest at December 31, 2020 508,866 0.33 0.8 2,774 Exercisable as of December 31, 2020 508,866 0.33 0.8 2,774 ​ The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the fair value of the underlying stock at each reporting date, for those awards that have an exercise price below the estimated fair value of the Company’s shares. As of December 31, 2020, the Company had options outstanding to purchase an aggregate of 508,866 shares with an exercise price below the fair value of the Company’s shares, resulting in an aggregate intrinsic value of RMB18,100 (US$2,774). The aggregate fair value of the outstanding options at the grant date was determined to be RMB6,014 (US$922) as of December 31, 2020 and such amount is recognized as share-based compensation expenses using the straight-line method for all employee share options granted with graded vesting based on service conditions and the accelerated method for share options granted with graded vesting based on performance conditions. The total fair value of share options exercised during the years ended December 31, 2018, 2019 and 2020 was US$239, US$42 and US$594, respectively. The aggregate intrinsic value of options exercised during the years ended December 31, 2018, 2019 and 2020 was US$248, US$22, and US$2,336, respectively. As of December 31, 2020, the Company has recorded all the share-based compensation expenses in relation to outstanding share options. The following table summarized the Company’s RSUs activity under the 2014 and 2020 Plan: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Weighted ​ ​ ​ ​ ​ average ​ average ​ Aggregate ​ ​ Number of ​ grant date ​ remaining ​ intrinsic ​ ​ RSUs ​ fair value ​ contractual life ​ value ​ ​ (US$) (Years) (US$) Unvested, January 1, 2020 ​ 2,696,129 ​ 6.83 ​ 7.8 ​ ​ Granted 2,163,543 22.62 ​ ​ Vested (433,905) 8.91 ​ ​ Forfeited (333,310) 6.59 ​ ​ Unvested, December 31, 2020 4,092,457 14.95 8.2 141,967 ​ 23. SHARE BASED COMPENSATION (CONTINUED) Option granted to employees (continued) Share-based compensation expenses for RSUs are measured based on the closing fair market value of the Company’s ADS on the date of grant and the reporting date for liability classified RSUs, respectively. The aggregate fair value of the unvested RSUs as of December 31, 2020 was RMB926,335 (US$141,967), and such amount is recognized as share-based compensation expenses using the straight-line method for the RSUs with graded vesting based on service conditions and the accelerated method for the RSUs with graded vesting based on performance conditions, market conditions and share-settled bonuses. The weighted average grant date fair value of RSUs granted during the years ended December 31, 2018, 2019 and 2020 was US$6.39, US$7.67 and US$22.62, respectively. The total fair value of RSUs vested during the years ended December 31, 2018, 2019 and 2020 was US$9,422, US$6,185 and US$3,866, respectively. As of December 31, 2020, there was RMB219,998 (US$33,716) of unrecognized share-based compensation expenses related to RSUs which is expected to be recognized over a weighted average vesting period of 2.5 years. Total unrecognized share-based compensation expenses may be adjusted for future changes when actual forfeitures incurred. Total share-based compensation expenses relating to share options and RSUs granted to employees recognized for the years ended December 31, 2018, 2019 and 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Cost of revenues 2,668 1,884 15,251 2,337 Sales and marketing expenses 2,139 354 38,247 5,862 General and administrative expenses 53,346 40,501 82,672 12,670 Research and development expenses 1,385 1,177 634 97 ​ 59,538 43,916 136,804 20,966 ​

TAXATION

TAXATION	12 Months Ended
	Dec. 31, 2020
TAXATION
TAXATION	24. TAXATION Enterprise income tax (“EIT”) Cayman Islands The Company is incorporated in the Cayman Islands and conducts its primary business operations through the subsidiaries and VIEs in the PRC and Hong Kong. Under the current laws of the Cayman Islands, the Company is not subject to tax on income or capital gain arising in Cayman Islands. British Virgin Islands Subsidiaries in British Virgin Islands are not subject to tax on income or capital gains under the current laws of the British Virgin Islands. Additionally, upon payments of dividends by the Company to its shareholders, no British Virgin Islands withholding tax will be imposed. Hong Kong Subsidiaries in Hong Kong are subject to Hong Kong profits tax rate of 16.5% for the years ended December 31, 2018, 2019 and 2020. Additionally, upon payments of dividends by the Company to its shareholders, no HK withholding tax will be imposed. ​ 24. TAXATION (CONTINUED) Enterprise income tax (“EIT”) (continued) Taiwan DYX Taiwan branch is incorporated in Taiwan and is subject to Taiwan profits tax rate of 20%, 20% and 20% respectively for the years ended December 31, 2018, 2019 and 2020. The PRC The Company’s PRC subsidiaries are incorporated in the PRC and subject to the statutory rate of 25% on the taxable income in accordance with the Enterprise Income Tax Law (The “EIT Law”), which was effective since January 1, 2008, except for certain entities eligible for preferential tax rates. Dividends, interests, rent or royalties payable by the Company’s PRC subsidiaries, to non-PRC resident enterprises, and proceeds from any such non-resident enterprise investor ’s disposition of assets (after deducting the net value of such assets) shall be subject to 10% withholding tax, unless the respective non-PRC resident enterprise’s jurisdiction of incorporation has a tax treaty or arrangements with China that provides for a reduced withholding tax rate or an exemption from withholding tax. 21Vianet Beijing was qualified for a High and New Technology Enterprise (“HNTE”) since 2008 and is eligible for a 15% preferential tax rate. In October 2014, 21Vianet Beijing obtained a new certificate and reapplied the certificate in October 2017 and 2020, with a validity term of three years. In accordance with the PRC Income Tax Laws, an enterprise awarded with the HNTE certificate may enjoy a reduced EIT rate of 15%. For the years ended December 31, 2018, 2019 and 2020, the tax rate for 21Vianet Beijing was 15%, 15% and 15%, respectively. In April 2011, Xi’an Sub, a subsidiary located in Shaanxi Province, was qualified for a preferential tax rate of 15% and started to apply this rate from then on. The preferential tax rate is awarded to companies that are located in West Regions of China which operate in certain encouraged industries. For the years ended December 31, 2018, 2019 and 2020, the tax rate assessed for Xi’an Sub was 15%, 15% and 15%, respectively. In October 2015, SH Blue Cloud, a subsidiary located in Shanghai, was qualified for a HNTE and became eligible for 15% preferential tax rate. The certificate was reapplied in November 2018 with a validity term of three years. Accordingly, for the years ended December 31, 2018, 2019 and 2020, SH Blue Cloud enjoyed a preferential tax rate of 15%. In November 2016, SZ DYX, a subsidiary located in Guangdong Province, was qualified for a HNTE and became eligible for 15% preferential tax rate effective for three The New EIT Law also provides that enterprises established under the laws of foreign countries or regions and whose “place of effective management” is located within the PRC are considered PRC tax resident enterprises and subject to PRC income tax at the rate of 25% on worldwide income. The definition of “place of effective management” refers to an establishment that exercises, in substance, overall management and control over the production and business, personnel, accounting, properties, etc. of an enterprise. ​ 24. TAXATION (CONTINUED) Enterprise income tax (“EIT”) (continued) The PRC (continued) As of December 31, 2020, the administrative practice associated with interpreting and applying the concept of “place of effective management” is unclear. If the Company is deemed as a PRC tax resident, it will be subject to 25% PRC EIT under the New EIT Law on its worldwide income, meanwhile the dividend it receives from another PRC tax resident company will be exempted from 25% PRC income tax. The Company will continue to monitor changes in the interpretation or guidance of this law. Loss before income taxes consisted of: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2018 2019 2020 ​ RMB RMB RMB US$ Non-PRC (214,063) (178,762) (2,708,101) (415,033) PRC 51,738 2,953 137,178 21,023 ​ (162,325) (175,809) (2,570,923) (394,010) ​ Income tax expenses comprised of: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2018 2019 2020 ​ RMB RMB RMB US$ Current (44,187) (70,324) (131,844) (20,206) Deferred 19,776 64,887 22,508 3,450 ​ (24,411) (5,437) (109,336) (16,756) ​ The reconciliation of tax computed by applying the statutory income tax rate of 25% for the years ended December 31, 2018, 2019 and 2020 applicable to the PRC operations to income tax expenses were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2018 2019 2020 ​ RMB RMB RMB US$ Loss before income taxes (162,325) (175,809) (2,570,923) (394,010) Income tax benefits computed at applicable tax rates (25%) 40,581 43,952 642,731 98,503 Non-deductible expenses (2,834) (23,082) (4,117) (631) Research and development expenses 25,906 19,688 32,777 5,023 Preferential rate 11,701 20,213 26,554 4,070 Current and deferred tax rate differences 37,934 (8,699) (36,391) (5,577) International rate differences (63,525) (77,066) (711,962) (109,113) Tax exempted income — 754 1,087 167 PRC withholding tax ​ — ​ — ​ (10,263) ​ (1,573) Unrecognized tax benefits (expenses) 1,472 1,728 (58,449) (8,958) Change in valuation allowance (79,694) 25,423 6,465 991 Prior year provision to return true up 4,048 (8,348) 2,232 342 Income tax expenses (24,411) (5,437) (109,336) (16,756) ​ 24. TAXATION (CONTINUED) Deferred Tax The significant components of deferred taxes were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2019 2020 ​ RMB RMB US$ Deferred tax assets Non-current Allowance for doubtful debt 48,568 39,886 6,113 Impairment of long-lived assets ​ — ​ 13,467 ​ 2,064 Impairment of long-term investment ​ — ​ 2,150 ​ 330 Accrued expense 21,139 24,986 3,829 Tax losses 146,996 171,211 26,239 Property and equipment 20,567 22,631 3,468 Intangible assets 3,691 5,765 884 Finance lease 395,555 390,925 59,912 Deferred government grant 1,189 1,357 208 Operating lease 269,468 292,210 44,783 Loss picked up on equity method investments ​ 56,706 ​ 57,201 ​ 8,766 Valuation allowance (158,638) (170,104) (26,070) ​ ​ ​ ​ ​ ​ ​ Total deferred tax assets, net of valuation allowance 805,241 851,685 130,526 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities Non-current Intangible assets 104,217 186,258 28,545 Property and equipment 81,424 143,873 22,050 Capitalized interest expense 15,146 19,339 2,963 Finance lease ​ 326,407 ​ 313,102 ​ 47,985 Operating lease ​ 269,468 ​ 292,210 ​ 44,783 Investment in subsidiaries ​ — ​ 10,263 ​ 1,573 Gain picked up from equity method investments 1,785 252 39 ​ ​ ​ ​ ​ ​ ​ Total non-current deferred tax liabilities ​ 798,447 ​ 965,297 ​ 147,938 ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets (liabilities) ​ 6,794 ​ (113,612) ​ (17,412) Analysis as: ​ ​ ​ ​ ​ ​ Deferred tax assets ​ 209,366 ​ 185,481 ​ 28,426 Deferred tax liabilities ​ 202,572 ​ 299,093 ​ 45,838 ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets (liabilities) 6,794 (113,612) (17,412) ​ As of December 31, 2020, the Company has net tax operating losses from its PRC subsidiaries and its Consolidated VIEs, as per filed tax returns, of RMB710,815 (US$108,937), which will expire between 2021 to 2030. As of December 31, 2020, the undistributed earnings of the Company’s PRC subsidiaries the Company intends to permanently reinvested were RMB1,262,028 (US$193,414). In 2020, other than these indefinitely reinvested amount, the Company has other operation or distribution plan for the new VIE, SH Zhiyan. As of December 31, 2020, the related PRC withholding tax liability accrued was RMB10,263 (US$1,573). ​ 24. TAXATION (CONTINUED) Unrecognized Tax Benefits As of December 31, 2019 and 2020, the Company recorded unrecognized tax benefits of RMB2,443 and RMB68,696 (US$10,528), respectively. The unrecognized tax benefits and its related interest are primarily related to non-deductible expenses and accrued expenses. RMB58,916 of the total unrecognized tax benefits, ultimately recognized, will impact the effective tax rate. It is possible that the amount of uncertain tax benefits will change in the next 12 months, however, an estimate of the range of the possible outcomes cannot be made at this time. A roll-forward of unrecognized tax benefits principle was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2019 2020 ​ RMB RMB US$ Balance at beginning of year 4,509 1,722 264 Reversal based on tax positions related to prior years (3,266) (629) (96) Additions based on tax positions related to the current year 479 61,491 9,423 Balance at end of year 1,722 62,584 9,591 ​ For the years ended December 31, 2018, 2019 and 2020, the Company reversed (recorded) interest expense of RMB (2,761), RMB (1,447) and RMB5,391 (US$826), respectively. Accumulated interest expense recorded by the Company was RMB721 and RMB6,112 (US$937) as of December 31, 2019 and 2020, respectively. As of December 31, 2020, the tax years ended December 31, 2015 through 2020 for the PRC subsidiaries remain open for statutory examination by the PRC tax authorities.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	12 Months Ended
	Dec. 31, 2020
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS	25. RELATED PARTY TRANSACTIONS a) ​ Name of related parties Relationship with the Company Xiaomi Ventures Limited (“Xiaomi”), Xiaomi Communication Technology Co.,Ltd., and its subsidiary, Beijing Xiaomi Mobile Software Co., Ltd.,(collectively, “Xiaomi Group”) (2) ​ A company controlled by principal shareholder of the Company before December 30, 2020 King Venture Holdings Limited (“King Venture”) and Beijing Kingsoft Cloud Network Technology Co., Ltd. (“BJ Kingsoft”) (1) ​ A company controlled by principal shareholder of the Company before December 30, 2020 Beijing Cheetah Mobile Technology Co., Ltd.(“BJ Cheetah”) (1) ​ A company controlled by principal shareholder of the Company before December 30, 2020 Unisvnet Technology Co., Ltd. (“Unisvnet”) ​ A company controlled by controlling shareholder of the Company Beijing Tuspark Harmonious Investment Development Co., Ltd. (“Tuspark Harmonious”) ​ A company controlled by controlling shareholder of the Company Ziguang Financial Leasing Co., Ltd. (“Ziguang Finance Leasing”) ​ A company controlled by principal shareholder of the Company Qidi Bus (Beijing) Technology Co., Ltd. (“Qidi Tech”) ​ A company controlled by controlling shareholder of the Company Beijing Qidi Yefeng Investment Co., Ltd. (“Beijing Qidi Yefeng”) ​ A company controlled by controlling shareholder of the Company Beijing Huaqing Property Management Co., Ltd. (“Beijing Huaqing”) ​ A company controlled by controlling shareholder of the Company Shanghai Shibei Hi-Tech Co., Ltd. (“SH Shibei”) ​ Noncontrolling shareholder of a subsidiary Marble Stone SH Group Limited (“Marble SH”) (4) ​ A company controlled by minority shareholder of the Company Marble Stone Holdings Limited (“Marble Holdings”) (4) ​ A company controlled by minority shareholder of the Company Shanghai Puping Information Technology Co., Ltd. (“Shanghai Puping”) (4) ​ A company controlled by minority shareholder of the Company Shihua DC Investment Holdings 2 Limited (“Shihua Holdings 2”) ​ Equity investee of the Company in 2018 and wholly-owned subsidiary since August 20, 2019 (Note 4) Beijing Chengyishidai Network Engineering Technology Co., Ltd.(“CYSD”) (3) ​ Equity investee of the Company WiFire (Beijing) Technology Co., Ltd. (“WiFire BJ”) (3) ​ Equity investee of the Company Beijing Fastweb Network Technology Co., Ltd. (“BJ Fastweb”) (3) ​ Equity investee of the Company Shanghai Fawei Technology Co., Ltd. (“SH Fawei”) (3) ​ Equity investee of the Company Wuhan Fastweb Cloud Computing Co., Ltd. (“WH Fastweb”) (3) ​ Equity investee of the Company Beijing Bozhi Ruihai Network Technology Co., Ltd. (“BZRH”) (3) ​ Equity investee of the Company WiFire (Shanghai) Network Technology Co., Ltd. (“SH Guotong”) (3) ​ Equity investee of the Company Jingliang Interconnected Cloud Technology Co., Ltd. (“Jingliang Inter Cloud”) ​ Equity investee of the Company Beijing Taiji Data Tech Co., Ltd. (“Taiji”) ​ Equity investee of the Company in 2018, 2019 and wholly-owned subsidiary since January 31, 2020 Shihua DC Investment Management Limited (“Shihua Investment Management”) ​ Equity investee of the Company in 2018, 2019 and wholly-owned subsidiary since January 31, 2020 Shihua DC Investment Management Group Limited (“Shihua Investment Group”) ​ Equity investee of the Company in 2018, 2019 and wholly-owned subsidiary since January 31, 2020 Apurimac Partners Limited (“APL”) ​ A company controlled by an officer of the Company Asialeads Capital (Cayman) Limited ​ A company in which a director of the Company acts as an executive ​ * These are the related parties that have engaged in significant transactions with the Company for the years ended December 31, 2018, 2019 and 2020. 25. RELATED PARTY TRANSACTIONS (CONTINUED) a) (1) These companies are ultimately controlled by the same party. King Venture made a significant investment in the Company in 2015. These companies ceased to be related parties as the Company repurchased the shares from King Venture on December 30, 2020. (2) These companies are ultimately controlled by the same party. Xiaomi made a significant investment in the Company in 2015. These companies ceased to be related parties as the Company repurchased the shares from King Venture on December 30, 2020. (3) These entities were disposed by the Company in September 2017, included in WiFire Entities, and determined by the Company as related parties as of December 31, 2018, 2019 and 2020. (4) These entities are controlled by Waburg Pincus, a significant minority shareholder of the Company. 25. RELATED PARTY TRANSACTIONS (CONTINUED) b) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2018 2019 2020 ​ RMB RMB RMB US$ Services provided to: -Xiaomi Group 374,085 ​ 437,694 527,679 80,870 -Qidi Tech ​ — ​ 7,427 ​ 3,478 ​ 533 -Jingliang Inter Cloud ​ — ​ — ​ 880 ​ 135 -BJ Cheetah ​ 2,079 ​ 169 ​ 98 ​ 15 -BJ Kingsoft 6,281 ​ 3,475 43 7 -Taiji ​ 13,681 ​ 7,899 ​ — ​ — -WiFire BJ 16,490 ​ 1,934 — — -Unisvnet 1,011 ​ — — — -Others 4,493 ​ 1,494 305 47 ​ ​ ​ ​ ​ ​ ​ ​ ​ Services provided by: -CYSD ​ 18,667 ​ 38,918 ​ 38,918 ​ 5,964 -BJ Kingsoft ​ 13,204 ​ 3,492 ​ 16,867 ​ 2,585 -APL — — 8,124 1,245 -Jingliang Inter Cloud 3,477 8,829 4,956 760 -Beijing Huaqing ​ — ​ — ​ 4,389 ​ 673 -Taiji 7,095 19,942 — — -DCSS 5,238 — — — -BZRH 4,239 — — — -WiFire BJ ​ 4,066 ​ — ​ — ​ — -Others 6,396 5,866 796 122 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loan to: -Shanghai Puping ​ — ​ — ​ 62,531 ​ 9,583 -Taiji ​ — ​ 1,500 ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest income from loan to: -BJ Fastweb 700 700 — — ​ ​ ​ ​ ​ ​ ​ ​ ​ Lease deposit paid to: ​ ​ ​ -Ziguang Finance Leasing ​ 2,042 ​ 6,154 ​ 135 ​ 21 -Tuspark Harmonious 11,472 — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ Lease payment paid to: -Tuspark Harmonious ​ — ​ 68,832 ​ 43,703 ​ 6,698 -Ziguang Finance Leasing 4,897 17,156 30,776 4,717 -Beijing Qidi Yefeng ​ — ​ — ​ 4,516 ​ 692 ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash consideration for shares repurchase ​ ​ ​ ​ ​ ​ ​ ​ -King Venture ​ — ​ — ​ 130,472 ​ 19,996 ​ During the year ended December 31, 2020, the company entered into an agreement with Asialeads Capital (Cayman) Limited purchased the Company’s convertible promissory notes for total gross proceeds of US$50,000. ​ 25. RELATED PARTY TRANSACTIONS (CONTINUED) c) ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2019 2020 ​ RMB RMB US$ Amounts due from related parties: Current: -Shanghai Puping ​ — ​ 62,531 ​ 9,583 -SH Shibei ​ 9,800 ​ 9,800 ​ 1,502 -Ziguang Finance Leasing ​ — ​ 2,042 ​ 313 -Marble SH (2) ​ 100,106 ​ — ​ — -Shihua Investment Group (3) ​ 82,542 ​ — ​ — -Xiaomi Group 39,778 — — -Marble Holdings (2) ​ 29,736 ​ — ​ — -Shihua Investment Management (3) ​ 27,905 ​ — ​ — -Taiji 9,499 — — -Qidi Tech ​ 1,249 ​ — ​ — -Others 1,050 1,146 176 ​ 301,665 75,519 11,574 Non-current: -Tuspark Harmonious 11,863 11,863 1,818 -Ziguang Finance Leasing 8,195 6,289 964 -Beijing Qidi Yefeng ​ — ​ 1,124 ​ 172 -Others ​ 596 ​ 1,286 ​ 197 ​ 20,654 20,562 3,151 Amounts due to related parties: Current: -Ziguang Finance Leasing 27,160 31,681 4,855 -Tuspark Harmonious 24,917 13,557 2,078 -Beijing Qidi Yefeng ​ — ​ 4,410 ​ 676 -Shihua Investment Group (3) ​ 84,021 ​ — ​ — -Shihua Investment Management (3) ​ 22,484 ​ — ​ — -WiFire BJ (1) ​ 6,330 ​ — ​ — -BJ Kingsoft 1,073 — — -APL ​ — ​ 783 ​ 120 -Others 950 576 88 ​ 166,935 51,007 7,817 Non-current: -Tuspark Harmonious 698,511 715,992 109,731 -Ziguang Finance Leasing 47,388 22,247 3,409 -Beijing Qidi Yefeng ​ — ​ 9,507 ​ 1,457 ​ 745,899 747,746 114,597 ​ (1) In 2019, RMB20,367 of amounts due from/to WiFire Entities were offset according to the multi-party debt offset agreement signed in 2019. The remaining RMB52,142 of amounts due from WiFire Entities was fully impaired considering low collectability. (2) Amounts due from Marble SH and Marble Holdings represented the unpaid cash consideration to the Company for acquiring the 100% equity interest in certain of Shihua Holdings 2’s subsidiaries in 2019 (Note 4). (3) Amounts due from/to Shihua Investment Management and Shihua Invesetment Group were generated from the assets acquisition of Shihua Holdings 2 (Note 4).

RESTRICTED NET ASSETS

RESTRICTED NET ASSETS	12 Months Ended
	Dec. 31, 2020
RESTRICTED NET ASSETS
RESTRICTED NET ASSETS	26. RESTRICTED NET ASSETS The Company’s ability to pay dividends is primarily dependent on the Company receiving distributions of funds from its subsidiaries. Relevant PRC statutory laws and regulations permit payments of dividends by the Company’s PRC subsidiaries only out of their retained earnings, if any, as determined in accordance with PRC accounting standards and regulations. The results of operations reflected in the consolidated financial statements prepared in accordance with U.S. GAAP differ from those reflected in the statutory financial statements of the Company’s PRC subsidiaries. In accordance with the PRC Regulations on Enterprises with Foreign Investment and the articles of association of the Company’s PRC subsidiaries, a foreign-invested enterprise established in the PRC is required to provide certain statutory reserves, namely general reserve fund, the enterprise expansion fund and staff welfare and bonus fund which are appropriated from net profit as reported in the enterprise’s PRC statutory accounts. A foreign-invested enterprise is required to allocate at least 10% of its annual after-tax profit to the general reserve until such reserve has reached 50% of its respective registered capital based on the enterprise’s PRC statutory accounts. Appropriations to the enterprise expansion fund and staff welfare and bonus fund are at the discretion of the board of directors for all foreign-invested enterprises. The aforementioned reserves can only be used for specific purposes and are not distributable as cash dividends. 21Vianet China was established as a foreign-invested enterprise and, therefore, is subject to the above mandated restrictions on distributable profits. As of December 31, 2019, and 2020, the Company’s PRC subsidiaries had appropriated RMB60,469 and RMB74,462 (US$11,412), respectively, in its statutory reserves. As a result of these PRC laws and regulations subject to the limit discussed above that require annual appropriations of 10% of after-tax income to be set aside, prior to payment of dividends as general reserve fund, the Company’s PRC subsidiaries are restricted in their ability to transfer a portion of their net assets to the Company. Amounts restricted include paid-in capital, additional paid in capital and statutory reserve funds of the Company’s PRC subsidiaries and the equity of the Consolidated VIEs, as determined pursuant to PRC generally accepted accounting principles, totaling an aggregate of RMB9,885,573 (US$1,515,030) as of December 31, 2020.

LOSS PER SHARE

LOSS PER SHARE	12 Months Ended
	Dec. 31, 2020
LOSS PER SHARE
LOSS PER SHARE	27. LOSS PER SHARE Basic and diluted loss per share for each of the years presented were calculated as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ Net loss (186,736) (181,246) (2,680,259) (410,766) Net profit attributable to noncontrolling interest (18,329) (1,046) (29,088) (4,458) Net loss attributable to the Company (205,065) (182,292) (2,709,347) (415,224) Plus undeclared cumulative dividend on perpetual convertible preferred shares — — (22,806) (3,495) Deemed distribution to perpetual convertible preferred shareholders ​ — ​ — ​ (470,643) ​ (72,129) Adjusted net loss attributable to ordinary shareholders (205,065) (182,292) (3,202,796) (490,848) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: Weighted average number of shares outstanding—basic ​ 674,732,130 ​ 668,833,756 ​ 716,888,919 ​ 716,888,919 Weighted average number of shares outstanding—diluted ​ 674,732,130 ​ 668,833,756 ​ 716,888,919 ​ 716,888,919 Loss per share—Basic: Net loss (0.30) (0.27) (4.47) (0.69) ​ (0.30) (0.27) (4.47) (0.69) Loss per share—Diluted: ​ Net loss (0.30) (0.27) (4.47) (0.69) ​ (0.30) (0.27) (4.47) (0.69) ​ In 2018, 2019 and 2020, the Company issued nil, 6,700,002 and nil ordinary shares to its share depositary bank which will be used to settle stock option awards upon their exercise, respectively. No consideration was received by the Company for this issuance of ordinary shares. These ordinary shares are legally issued and outstanding but are treated as escrowed shares for accounting purposes and therefore, have been excluded from the computation of loss per share. Any ordinary shares not used in the settlement of stock option awards will be returned to the Company.

SHARE CAPITAL

SHARE CAPITAL	12 Months Ended
	Dec. 31, 2020
SHARE CAPITAL
SHARE CAPITAL	28. SHARE CAPITAL Holders of Class A Ordinary Shares, Class B Ordinary Shares and Class C Ordinary Shares are entitled to the same rights except for voting and conversion rights. In respect of matters requiring a shareholder’s vote, each Class A Ordinary Share is entitled to one vote right, each Class B Ordinary Share is entitled to ten votes, and each Class C Ordinary Share is entitled to one vote and certain veto rights. Each Class B Ordinary Share and Class For the years ended December 31, 2018 and 2019, 3,070,500 and 304,200 Class A ordinary shares were issued to settle the share options exercised and RSUs vested. For the year ended December 31, 2020, 104,304 Class A ordinary shares issued to settle RSUs vested in prior years were repurchased and cancelled. In October 2019, the Company issued 60,000 newly created Class C ordinary shares to Personal Group Limited, a British Virgin Islands company wholly owned by Mr. Sheng Chen, the executive chairman of our board of directors, at a price of US$1.35 per share, to execute business strategies over the long term under the leadership of the Company’s board and senior management. In August 2020, the Company completed a public offering in which the Company offered and sold 19,550,000 ADSs (or 117,300,000 Class A ordinary shares), including 2,550,000 ADSs (or 15,300,000 Class A ordinary shares) purchased by the underwriters by exercising their option. The Company raised a total of RMB2,680,421 (US$410,792) in proceeds from this public offering, net of underwriting discounts and commissions and other issuance costs. In 2020, Purchaser of the convertible promissory notes exercised the right to convert approximately 23.7% of the total principal amount issued to 23,710,140 newly issued Class A ordinary shares at the conversion price of US$12 per ADS.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2020
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS	29. FAIR VALUE MEASUREMENTS The Company applies ASC 820. ASC 820 defines fair value, establishes a framework for measuring fair value and expands disclosures about fair value measurements. ASC 820 requires disclosures to be provided on fair value measurement. ASC 820 establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1 — Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 — Include other inputs that are directly or indirectly observable in the marketplace. Level 3 — Unobservable inputs which are supported by little or no market activity. ASC 820 describes three main approaches to measuring the fair value of assets and liabilities: (1) market approach; (2) income approach; and (3) cost approach. The market approach uses prices and other relevant information generated from market transactions involving identical or comparable assets or liabilities. The income approach uses valuation techniques to convert future amounts to a single present value amount. The measurement is based on the value indicated by current market expectations about those future amounts. The cost approach is based on the amount that would currently be required to replace an asset. Cash equivalents, time deposits and bonds payable are classified within Level 1 because they are valued by using quoted market prices. ​ 29. FAIR VALUE MEASUREMENTS (CONTINUED) The contingent considerations for the acquired businesses, convertible promissory notes, liability classified RSU and long-term investments are classified within Level 3. The contingent considerations are based on the achievement of certain financial targets in accordance with the sales and purchase agreements for the various periods, as well as other non-financial measures. The fair value of liability classified RSU was estimated using the share price and exchange rate that the Company estimates to be settled in shares. The fair value of convertible promissory notes is measured using binomial tree pricing model that involves several parameters including the Company’s stock price, stock price volatility determined from the Company’s historical stock prices, the remaining maturity term and the discount rate. The Company measures equity investments elected to use the measurement alternative at fair value on a nonrecurring basis, in the cases of an impairment charge is recognized, fair value of an investment is remeasured in an acquisition/a disposal, and an orderly transaction for identical or similar investments of the same issuer was identified. Assets and liabilities measured at fair value on a recurring basis were summarized below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurement using: ​ ​ Quoted prices in ​ Significant other ​ ​ ​ ​ ​ ​ active markets for ​ observable ​ Unobservable ​ ​ ​ ​ identical assets ​ inputs ​ inputs ​ Fair value at ​ ​ (Level 1) ​ (Level 2) ​ (Level 3) ​ December 31, 2019 ​ RMB RMB RMB RMB Cash equivalents: - Time deposits 117,825 — — 117,825 Short-term investments: ​ ​ - Time deposits 363,856 — — 363,856 Long-term investments - Available-for-sale debt securities — — 1,713 1,713 Assets 481,681 — 1,713 483,394 ​ ​ ​ ​ ​ ​ ​ ​ ​ Short-term borrowings: ​ ​ ​ ​ ​ ​ ​ ​ - Current portion of bonds payable ​ 912,416 ​ — ​ — ​ 912,416 Long-term borrowings: - Bonds payable 2,089,114 — — 2,089,114 Other liabilities: - Liability classified RSU — — 2,109 2,109 Liabilities 3,001,530 — 2,109 3,003,639 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurement using: ​ ​ ​ ​ ​ ​ Quoted prices in ​ Significant other ​ ​ ​ ​ ​ ​ ​ ​ active markets for ​ observable ​ Unobservable ​ ​ ​ ​ ​ ​ identical assets ​ inputs ​ inputs ​ Fair value at ​ ​ (Level 1) ​ (Level 2) ​ (Level 3) ​ December 31, 2020 ​ RMB RMB RMB RMB US$ Cash equivalents: - Time deposits 645,879 — — 645,879 98,985 Short-term investments: - Time deposits 285,872 — — 285,872 43,812 Long-term investments: ​ ​ ​ ​ ​ - Available-for-sale debt securities — — 1,713 1,713 263 Assets 931,751 — 1,713 933,464 143,060 Short-term borrowings: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ - Current portion of bonds payable ​ 1,998,088 ​ — ​ — ​ 1,998,088 ​ 306,220 Convertible promissory notes ​ — ​ — ​ 3,014,057 ​ 3,014,057 ​ 461,924 Other liabilities: ​ - Liability classified RSU — — — — — Liabilities 1,998,088 — 3,014,057 5,012,145 768,144 ​ 29. FAIR VALUE MEASUREMENTS (CONTINUED) The following table presented a reconciliation of all liabilities measured at fair value on a recurring basis using significant unobservable inputs (level 3): ​ ​ ​ ​ ​ Liability classified ​ ​ RSU ​ ​ RMB Fair value at January 1, 2019 4,970 Reclassification to equity (2,861) Reversal ​ — Transfers in and/or out of Level 3 — Fair value at December 31, 2019 2,109 Reclassification to equity (2,109) Reversal — Transfers in and/or out of Level 3 — Fair value at December 31, 2020 — Fair value at December 31, 2020 (US$) — ​ ​ ​ ​ ​ ​ ​ Convertible promissory notes ​ ​ RMB ​ US$ Convertible promissory notes fair value (Note 18) 1,409,385 215,998 Foreign exchange loss (219,001) (33,564) Changes in the fair value 2,544,220 389,919 Reclassification to equity (720,547) (110,429) Transfers in and/or out of Level 3 — — Fair value at December 31, 2020 3,014,057 461,924 ​ Assets measured at fair value on a non-recurring basis The Company measures certain non-financial assets on a nonrecurring basis. The Company’s non-financial long-lived assets , such as intangible assets, goodwill and fixed assets, would be measured at fair value only if they were determined to be impaired on an other-than-temporary basis. The fair values of non-financial long-lived assets were measured under income approach, based on the Company’s best estimation which primarily includes significant unobservable inputs (level 3) such as future cash flows and discount rate.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2020
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	30. COMMITMENTS AND CONTINGENCIES Capital commitments As of December 31, 2020, the Company has the following commitments to purchase certain computer and network equipment and construction-in-progress: ​ ​ ​ ​ ​ ​ ​ RMB US$ For the year ending December 31, ​ ​ ​ ​ 2021 ​ 1,678,273 ​ 257,207 2022 and thereafter — — ​ 1,678,273 257,207 ​ Bandwidth and cabinet capacity purchase commitments As of December 31, 2020, the Company has outstanding purchase commitments in relation to bandwidth and cabinet capacity consisting of the following: ​ ​ ​ ​ ​ ​ ​ RMB US$ For the year ending December 31, ​ ​ ​ ​ 2021 706,715 108,309 2022 149,331 22,886 2023 6,458 990 2024 2,189 335 2025 and thereafter 6,512 998 ​ 871,205 133,518 ​ Income Taxes As of December 31, 2020, the Company has recognized an accrual of RMB68,696 (US$10,528) for unrecognized tax benefits and its interest (Note 24). The final outcome of the tax uncertainty is dependent upon various matters including tax examinations, interpretation of tax laws or expiration of status of limitation. However, due to the uncertainties associated with the status of examinations, including the protocols of finalizing audits by the relevant tax authorities, there is a high degree of uncertainty regarding the future cash outflows associated with these tax uncertainties. Securities Litigation In 2014, the Company and certain of its officers and directors were named as defendants in two putative securities class actions filed in U.S. federal district courts in Texas, the complaints in both actions alleged that certain of the Company’s financial statements and other public disclosures contained misstatements or omissions and asset claims under the U.S. securities laws. In 2016, the Company filed a motion to dismiss the complaint and in 2017, the magistrate judge issued a report and recommendation to deny the Company’s motion to dismiss. On April 9, 2018, the lead plaintiff of the putative class action filed an unopposed motion for preliminary approval of settlement for both of the aforementioned class actions, requesting that, among others, the Court preliminarily approve a settlement agreement that the parties reached to settle the case for RMB58,808. On November 9, 2018, the Court approved the settlement and issued final judgment, ending the case. The Company has paid the settlement amount as of December 31, 2018. ​ 30. COMMITMENTS AND CONTINGENCIES (CONTINUED) Operating litigation In March 2019, a third-party supplier filed a lawsuit against the Company, alleging that the Company had not fully fulfilled its obligations under a network infrastructure cooperation agreement entered into in 2013. ​ On October 30, 2020, the court announced the first judgement settlement and the settlement came into force from November 18, 2020. The Company assessed that the settlement is probable and recorded an estimated loss of RMB1,628 (US$250) within accrued expenses and other payables in the consolidated balance sheet as of December 31, 2020. In the ordinary course of business, the Company may from time to time be involved in legal proceedings and litigations. As of December 31, 2020, the Company did not consider an unfavorable outcome in any material respects in the outstanding legal proceedings and litigations to be probable.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2020
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	31. SUBSEQUENT EVENTS In January 2021, the Company has issued a zero-coupon rate convertible senior notes for a total aggregate principal amount of US$600,000. The convertible notes will mature in five years from the date of issuance if not converted. On March 1, 2021, 150,000 Series A perpetual convertible preferred shares has been converted into 54,570,816 Class A Ordinary Shares. In April 2021, the Company repurchased from Tuspark Innovation Venture Ltd., (“Tuspark”) 48,634,493 Class B ordinary shares for an aggregate purchase price of approximately US$260 million. The repurchase price will be at US$5.346 per ordinary share, or US$32.076 per ADS. The director appointed by Tuspark has resigned from the board of directors of the Company. Immediately following the consummation of the transaction, all of the remaining Class B ordinary shares held by Tuspark have been converted into the same number of Class A ordinary shares of the Company. Tuspark has also agreed to sell and transfer additional ordinary shares to Beacon Capital Group Inc., a company affiliated with Mr. Josh Sheng Chen, at the same price. If this additional share transfer is consummated, Tuspark will retain a small shareholding of less than 5% in the Company.

PARENT COMPANY ONLY CONDENSED F

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION	12 Months Ended
	Dec. 31, 2020
PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION
PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION	32. PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION Condensed balance sheets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ Notes ​ 2019 ​ 2020 ​ ​ RMB RMB US$ ASSETS Current assets Cash and cash equivalents ​ ​ 243,989 62,116 9,520 Short-term investments ​ ​ 138,848 — — Prepaid expenses and other current assets ​ ​ 105,597 97,391 14,925 Amounts due from subsidiaries (b) 6,128,595 9,320,580 1,428,441 Total current assets ​ ​ 6,617,029 9,480,087 1,452,886 ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current assets ​ ​ Investments in subsidiaries ​ ​ 1,446,563 2,169,222 332,448 Total non-current assets ​ ​ 1,446,563 2,169,222 332,448 Total assets ​ ​ 8,063,592 11,649,309 1,785,334 LIABILITIES AND SHAREHOLDERS’ EQUITY ​ ​ ​ Current liabilities: ​ ​ ​ Accrued expenses and other payables ​ ​ 57,612 49,648 7,609 Account payables ​ ​ 56 52 8 Interest payable ​ ​ 58,525 37,353 5,725 Current portion of bonds payable ​ ​ ​ 911,147 ​ 1,943,619 ​ 297,873 Amount due to related parties ​ — 783 120 Amounts due to subsidiaries (b) 22,471 38,863 5,955 Total current liabilities ​ ​ 1,049,811 2,070,318 317,290 ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current liabilities ​ ​ Bonds payable (c) 2,060,708 — — Convertible promissory notes ​ ​ ​ — ​ 3,014,057 ​ 461,924 Total non-current liabilities ​ ​ 2,060,708 3,014,057 461,924 Total liabilities ​ ​ 3,110,519 5,084,375 779,214 Shareholders’ equity: ​ ​ ​ ​ Class A Ordinary shares (par value of US$0.00001 per share; 1,200,000,000 and 1,199,790,000 shares authorized; 505,253,850 and 672,024,600 shares issued outstanding ​ ​ 34 44 7 Class B Ordinary shares (par value of US$0.00001 per share; 300,000,000 and 300,000,000 shares authorized; 174,649,638 and 145,875,113 shares issued outstanding ​ ​ 12 12 2 Class C Ordinary shares (par value of US$0.00001 per share; 60,000 and 60,000 shares authorized; 60,000 and 60,000 shares issued outstanding ​ ​ ​ — ​ — ​ — Series A perpetual convertible preferred shares (par value of US$0.00001 per share; nil and 150,000 shares issued and outstanding ​ ​ ​ — ​ 1,047,468 ​ 160,531 Additional paid-in capital ​ ​ 9,202,567 13,083,119 2,005,076 Accumulated other comprehensive loss (income) ​ ​ 77,904 (55,535) (8,511) Accumulated deficit ​ ​ (3,977,921) (7,160,651) (1,097,418) Treasury stock ​ ​ (349,523) (349,523) (53,567) Total shareholders’ equity ​ ​ 4,953,073 6,564,934 1,006,120 Total liabilities and shareholders’ equity ​ ​ 8,063,592 11,649,309 1,785,334 ​ 32. PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION (CONTINUED) Condensed statements of operations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Operating Expenses General and administrative expenses (65,949) (44,490) (94,175) (14,433) Changes in the fair value of contingent purchase consideration payables 13,905 — — — Operating loss (52,044) (44,490) (94,175) (14,433) Other loss (262,186) (274,572) (168,656) (25,846) Changes in the fair value of convertible promissory notes ​ — ​ — ​ (2,544,220) ​ (389,919) Share of profits from subsidiaries and Consolidated VIEs 109,165 136,770 97,704 14,974 Net loss attributable to 21Vianet Group, Inc. (205,065) (182,292) (2,709,347) (415,224) Income tax expense — — — — Net loss (205,065) (182,292) (2,709,347) (415,224) ​ Condensed statements of comprehensive loss ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Net loss (205,065) (182,292) (2,709,347) (415,224) Other comprehensive income (loss), net of tax of nil: ​ ​ Foreign currency translation adjustments, net of tax of nil 88,652 (8,075) (133,439) (20,450) Other comprehensive income (loss), net of tax of nil: 88,652 (8,075) (133,439) (20,450) Comprehensive loss (116,413) (190,367) (2,842,786) (435,674) Comprehensive loss attributable to 21Vianet Group, Inc. (116,413) (190,367) (2,842,786) (435,674) ​ Condensed statements of cash flows ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Net cash used in operating activities (166,068) (142,989) (743,944) (114,014) Net cash used in investing activities (203,651) (1,011,257) (3,036,370) (465,344) Net cash generated from financing activities 43,145 807,765 3,598,441 551,485 Net decrease in cash and cash equivalents and restricted cash (326,574) (346,481) (181,873) (27,873) Cash and cash equivalents and restricted cash at beginning of the year 917,044 590,470 243,989 37,393 Cash and cash equivalents and restricted cash at end of the year 590,470 243,989 62,116 9,520 ​ ​ 32. PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION (CONTINUED) (a) Basis of presentation In the Company-only financial statements, the Company’s investment in subsidiaries is stated at cost plus equity in undistributed earnings of subsidiaries since inception. The Company records its investment in its subsidiary under the equity method of accounting as prescribed in ASC 323-10, Investment-Equity Method and Joint Ventures The subsidiaries did not pay any dividends to the Company for the years presented. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted and as such, these Company-only financial statements should be read in conjunction with the Company’s consolidated financial statements. (a) Related party transactions The Company had the following related party balances as of December 31, 2019 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Amounts due from subsidiaries - 21Vianet HK 5,855,452 7,043,586 1,079,477 - WiFire Open Network Group Ltd. ​ 147,326 ​ 2,157,285 ​ 330,618 - HongKong Fastweb Holdings Co., Ltd. 67,088 62,780 9,621 - 21V Mobile 58,018 56,265 8,623 - WiFire Group 698 652 100 - Others 13 12 2 ​ 6,128,595 9,320,580 1,428,441 Amounts due to subsidiaries - 21Vianet Beijing 19,449 35,783 5,484 - Others 3,022 3,080 471 ​ 22,471 38,863 5,955 ​

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2020
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Basis of presentation	(a) Basis of presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”).
Principles of consolidation	(b) Principles of consolidation The consolidated financial statements include the financial statements of the Company, its subsidiaries and the Consolidated VIEs for which the Company or a subsidiary of the Company is the primary beneficiary. All significant inter-company transactions and balances between the Company, its subsidiaries and the Consolidated VIEs are eliminated upon consolidation. Results of acquired subsidiaries and its Consolidated VIEs are consolidated from the date on which control is transferred to the Company.
Use of estimates	(c) Use of estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the period. Significant estimates and assumptions reflected in the Company’s financial statements include, but are not limited to, determining the valuation allowance for deferred tax assets, determining the fair value of convertible promissory notes and assessing the initial valuation of the assets acquired and liabilities assumed in acquisitions. Changes in facts and circumstances may result in revised estimates. Given the global economic climate and unforeseen effects from COVID-19 pandemic, the process of estimation has become more challenging. Actual results could differ from those estimates, and as such, differences may be material to the consolidated financial statements.
Foreign currency	(d) Foreign currency The functional currency of the Company and its overseas subsidiaries is the United States dollar (“US$”), whereas the functional currency of the Company’s PRC subsidiaries and its Consolidated VIEs is the Chinese Renminbi (“RMB”) as determined based on the criteria of ASC Topic 830, Foreign Currency Matters The financial statements of the Company and its overseas subsidiaries are translated from the functional currency to the reporting currency, RMB. Transactions denominated in foreign currencies are re-measured into the functional currency at the exchange rates prevailing on the transaction dates. Monetary assets and liabilities denominated in foreign currencies are re-measured at the exchange rates prevailing at the balance sheet date. Non-monetary items that are measured in terms of historical costs in foreign currency are re-measured using the exchange rates at the dates of the initial transactions. Exchange gains and losses are included in the consolidated statements of operations. The Company uses the average exchange rate for the year and the exchange rate at the balance sheet date to translate the operating results and financial position, respectively. Translation differences are recorded in accumulated other comprehensive income (loss) within the statements of comprehensive loss.
Convenience translation	(e) Convenience translation Amounts in US$ are presented for the convenience of the reader and are translated at the noon buying rate of US$1.00 to RMB6.5250 on December 31, 2020, the last business day in fiscal year 2020, representing the noon buying rate set forth in the H.10 statistical release of the U.S. Federal Reserve Board. No representation is made that the RMB amounts could have been, or could be converted, realized or settled into US$ at such rate or at any other rate. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
Cash and cash equivalents	(f) Cash and cash equivalents Cash and cash equivalents consist of cash on hand and demand deposits placed with banks which are unrestricted as to withdrawal and use and have original maturities less than three months. All highly liquid investments with a stated maturity of 90 days or less from the date of purchase are classified as cash equivalents.
Restricted cash	(g) Restricted cash Restricted cash mainly represents amounts held by a few banks in escrow as security for credit facilities, the guarantee of compliance with the network and service requirements of the radio spectrum license awarded by the Hong Kong Telecommunication Authority, the deposits for finance lease, the deposits for a lawsuit with a third party, the deposits held in escrow for the advances received from end customers subscribing Office 365 and Windows Azure services (the disbursement of which shall be agreed by both Microsoft (China) Co., Ltd. (“Microsoft”) and the Company), the deposits for business operation, the deposits for loans.
Short-term investments	(h) Short-term investments All highly liquid investments with original maturities of greater than three months but less than twelve months, are classified as short-term investments. Interest income is included in earnings.
Accounts receivable and allowance for doubtful debt	(i) Accounts receivable and allowance for doubtful debt Prior to adopting ASC 326, Financial Instruments-Credit Losses Receivables On January 1, 2020, the Company adopted ASC326 using modified-retrospective transition approach. Following the adoption of this guidance, a cumulative-effect adjustment in accumulated deficit of RMB2,740 was recognized as of January 1, 2020. For the year ended December 31, 2020, the Company recorded credit losses of RMB2,393 (US$367). Pursuant to ASC 326, an allowance for credit losses for financial assets, including accounts receivable, carried at amortized cost to present the net amount expected to be collected as of the balance sheet date. Such allowance is based on credit losses expected to arise over the life of the asset’s contractual term, which includes consideration of prepayments. Assets are written off when the Company determines that such financial assets are deemed uncollectible and are recognized as a deduction from the allowance for credit losses. Expected recoveries of amounts previously written off, not to exceed the aggregate of the amount previously written off, are included in determining the necessary reserve at the balance sheet date. The Company pools financial assets based on similar risk characteristics to estimate expected credit losses. The Company estimates expected credit losses on financial assets individually when those assets do not share similar risk characteristics. The Company closely monitors its accounts receivable including timely account reconciliations, detailed reviews of past due accounts, updated credit limits, and monthly analysis of the adequacy of their reserve for credit losses. The Company utilizes a loss rate approach to determine lifetime expected credit losses for its financial assets. This method is used for calculating an estimate of losses based primarily on the Company’s historical loss experience. In determining loss rates, the Company evaluates information related to historical losses, adjusted for current conditions and further adjusted for the period of time that the Company can reasonably forecast. The Company has concluded that it can reasonably support a forecast period for the contractual life of its financial assets. Qualitative and quantitative adjustments related to current conditions and the reasonable and supportable forecast period consider the following: the customer or vendor ’s creditworthiness, changes in the policy and procedures to establish customer credit limits, changes in the payment terms of receivables, existence and effect of any concentration of credit and changes in the level of such concentrations, and the effects of other external forces such as the current and forecasted direction of the economic and business environment.
Property and equipment	(j) Property and equipment Property and equipment are stated at cost less accumulated depreciation and any recorded impairment. Property and equipment acquired in a business combination are recognized initially at fair value at the data of acquisition. Property and equipment are depreciated using the straight-line method over the estimated useful lives of the assets, as follows: ​ ​ ​ ​ Category Estimated useful life Property 25-46 years Leasehold improvements Over the shorter of lease term or the estimated useful lives of the assets Optical fibers 10-20 years Computer and network equipment 1-10 years Office equipment 2-8 years Motor vehicles 2-8 years ​ Repair and maintenance costs are charged to expense as incurred, whereas the costs of betterments that extend the useful life of property and equipment are capitalized as additions to the related assets. Retirements, sale and disposals of assets are recorded by removing the cost and accumulated depreciation with any resulting gain or loss reflected in the consolidated statements of operations. Property and equipment that are purchased or constructed which require a period of time before the assets are ready for their intended use are accounted for as construction-in-progress. Construction-in-progress is recorded at acquisition cost, including installation costs. Construction-in-progress is transferred to specific property and equipment accounts and commences depreciation when these assets are ready for their intended use.
Intangible assets	(k) Intangible assets Intangible assets are carried at cost less accumulated amortization and any recorded impairment. Intangible assets acquired in a business combination are recognized initially at fair value at the date of acquisition. Intangible assets with finite useful lives are amortized using a straight-line method. These amortization methods reflect the estimated pattern in which the economic benefits of the respective intangible assets are to be consumed. The Company has capitalized certain internal use software development costs in accordance with ASC Subtopic 350-40, Intangibles-Goodwill and Other: Internal-Use Software Intangible assets have weighted average useful lives from the date of purchase/ acquisition as follows: ​ ​ ​ ​ Purchased software 5.1 years Radio spectrum license 15 years Operating permits* ​ 29.3 years Contract backlog* 4.9 years Customer relationships* 8.8 years Licenses* 15 years Supplier relationships* 10 years Trade Names* 20 years Platform software* 5 years Non-complete agreements* 5 years Internal use software 3.8 years Customer contract* ​ 6.5 years ​ * Acquired in the acquisitions of subsidiaries. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (l) Leases Effective January 1, 2019, the Company adopted ASC Topic 842, Lease The Company has elected the package of practical expedients, which allows the Company not to reassess (1) whether any expired or existing contracts as of the adoption date are or contain a lease, (2) lease classification for any expired or existing leases as of the adoption date and (3) initial direct costs for any expired or existing leases as of the adoption date. The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. Lastly, the Company elected the short-term lease exemption for all contracts with lease term of 12 months or less. At the commencement date of a lease, the Company determines the classification of the lease based on the relevant factors present and records a right-of-use (“ROU”) asset and lease liability for operating lease, and records property and equipment and finance lease liability for finance lease. ROU assets and property and equipment acquired through lease represent the right to use an underlying asset for the lease term, and operating lease liabilities and finance lease liabilities represent the obligation to make lease payments arising from the lease. ROU assets and lease liabilities are calculated as the present value of the lease payments not yet paid. If the rate implicit in the Company’s leases is not readily available, the Company uses an incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. This incremental borrowing rate reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. ROU assets include any lease prepayments and are reduced by lease incentives. Operating lease expense for lease payments is recognized on a straight-line basis over the lease term. Lease terms are based on the non-cancelable term of the lease and may contain options to extend the lease when it is reasonably certain that the Company will exercise that option. Leases with an initial lease term of 12 months or less are not recorded on the consolidated balance sheets. Lease expense for these leases is recognized on a straight-line basis over the lease term.
Leases	​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
Land use rights	(m) Land use right The land use rights represent the operating lease prepayments for the rights to use the land in the PRC under ASC 842. Amortization of the prepayments is provided on a straight-line basis over the terms of the respective land use rights certificates.
Long-term investments	(n) Long-term investments The Company’s long-term investments primarily consist of equity investments without readily determinable fair value, equity method investments. Pursuant to ASC Topic 321, Investments—Equity Securities Fair Value Measurements and Disclosures For equity investments measured at fair value with changes in fair value recorded in earnings, the Company does not assess whether those securities are impaired. For those equity investments that the Company elects to use the measurement alternative, the Company makes a qualitative assessment of whether the investment is impaired at each reporting date. If a qualitative assessment indicates that the investment is impaired, the entity has to estimate the investment’s fair value in accordance with the principles of ASC 820. If the fair value is less than the investment’s carrying value, the entity has to recognize an impairment loss in net loss equal to the difference between the carrying value and fair value. Investments in equity investees represent investments in entities in which the Company can exercise significant influence but does not own a majority equity interest or control are accounted for using the equity method of accounting in accordance with ASC Subtopic 323-10, Investments-Equity Method and Joint Ventures: Overall
Goodwill	(o) Goodwill Goodwill represents the excess of the purchase price over the amounts assigned to the fair value of the assets acquired and the liabilities assumed of an acquired business. In accordance with ASC Topic 350, Goodwill and Other Intangible Assets In accordance with ASC 350, the Company assigned and assessed goodwill for impairment at the reporting unit level. A reporting unit is an operating segment or one level below the operating segment. As of December 31, 2018, 2019 and 2020, there is only hosting and related services and the Company as a whole is one reporting unit. Pursuant to ASC 350, in 2019 and 2020, the Company performed a qualitative assessment for hosting and related services and completed its annual impairment test for goodwill that has arisen out of its acquisitions. The Company evaluated all relevant factors including, but not limited to, macroeconomic conditions, industry and market conditions, financial performance, and the share price of the Company. The Company weighed all factors in their entirety and concluded that it was not more-likely-than-not the fair value was less than the carrying amount of the reporting unit, and further impairment testing on goodwill was unnecessary. No impairment loss of goodwill in hosting and related services was recognized for the years ended December 31, 2018, 2019 and 2020. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
Impairment of long-lived assets	(p) Impairment of long-lived assets The Company evaluates long-lived assets, such as fixed assets and purchased or internally developed intangible assets with finite lives for impairment whenever events or changes in circumstances indicate the carrying value of an asset may not be recoverable in accordance with ASC Topic 360, Property, Plant and Equipment . When such events occur, the Company assesses the recoverability of the asset group based on the undiscounted future cash flows the asset group is expected to generate and recognizes an impairment loss when estimated undiscounted future cash flows expected to result from the use of the asset group plus net proceeds expected from disposition of the asset group, if any, is less than the carrying value of the asset group. If the Company identifies an impairment, the Company reduces the carrying amount of the asset group to its estimated fair value based on a discounted cash flow approach or, when available and appropriate, to comparable market values and the impairment loss, if any, is recognized in the consolidated statements of operations. As of December 31, 2020, due to continuing losses, the Company recorded the long-lived assets impairment amounting to RMB81,619 (US$12,509) for one of its asset groups, resulting from excess of the carrying amount of the asset group over the fair value of the asset group. The Company determined the fair value of the asset group using the income approach based on the discounted cash flows associated with the asset group. The discounted cash flows were based on a six-year projection for the asset group, which is consistent with the remaining useful life of its principal asset. The discount rate of 13% was derived and used in the valuations which reflect the market assessment of the risks specific to the Company and its industry and is based on its weighted average cost of capital. No impairment was recognized in other asset groups as there was no impairment indicator identified. The impairment loss reduced the carrying amount of the long-lived assets of the group on a pro-rata basis using the relative carrying amount of those assets except that the loss allocated to an individual long-lived asset of the group shall not reduce the carrying amount of that asset below its fair value whenever that fair value is determinable without undue cost and effort. The Company recorded impairment charges associated with its long-lived assets and acquired intangibles as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Impairment of equipment — — 35,793 5,486 Impairment of intangible assets — — 38,654 5,924 Impairment of other non-current assets — — 7,172 1,099
Fair value of financial instruments	(q) Fair value of financial instruments The Company’s financial instruments include cash and cash equivalents, restricted cash, short-term investments, accounts receivable and payable, other receivables and payables, bonds payable, short-term and long-term borrowings, available-for-sale investments, liability classified restricted share units (“RSU”) and convertible promissory notes. Other than the bonds payable, long-term borrowings and convertible promissory notes, the carrying values of these financial instruments approximate their fair values due to their short-term maturities. The carrying amounts of bonds payable and long-term borrowings approximate their fair values since they bear interest rates which approximate market interest rates. The Company carries the bonds payable at face value less unamortized debt discount and issuance cost on its consolidated balance sheets and measures the fair value for disclosure purposes only. The Company elected the fair value option of convertible promissory notes when it initially recognized as financial liability as the fair value better represents the value of the underlying liabilities. The contingent purchase considerations in both cash and shares and share-settled bonus are initially measured at fair value on the acquisition dates of the acquired businesses and the date of grant, respectively, and subsequently remeasured at the end of each reporting period with an adjustment for fair value recorded to the current period income/(expense). Convertible promissory notes are measured at fair value in accordance with ASC 825, Financial Instruments
Revenue recognition	(r) Revenue recognition The Company provides hosting and related services including hosting of customers’ servers and networking equipment, connecting customers’ servers with internet backbones (“Hosting service”), virtual private network services providing encrypted secured connection to public internet (“VPN service”) and other value-added services and public cloud service through strategic partnership with Microsoft. On January 1, 2018, the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers Revenue Recognition Under ASC 606, an entity recognizes revenue as the Company satisfies a performance obligation when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. Once a contract is determined to be within the scope of ASC 606 at contract inception, the Company reviews the contract to determine which performance obligations it must deliver and which of these performance obligations are distinct. The Company recognizes revenue based on the amount of the transaction price that is allocated to each performance obligation when that performance obligation is satisfied or as it is satisfied. The Company is a principal and records revenue on a gross basis when the Company is primarily responsible for fulfilling the service, has discretion in establishing pricing and controls the promised service before transferring that service to customers. Otherwise, the Company records revenue at the net amounts as commissions. 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (r) Revenue recognition (continued) The Company’s revenue recognition policies effective on the adoption date of ASC 606 are as follows: Hosting services are services that the Company dedicates data center space to house customers’ servers and networking equipment and provides tailored server administration services including operating system support and assistance with updates, server monitoring, server backup and restoration, server security evaluation, firewall services, and disaster recovery. The Company also provides interconnectivity services to connect customers with each other, internet backbones in China and other networks through Border Gateway Protocol, or BGP, network, or single-line, dual-line or multiple-line networks. Hosting services are typically provided to customers for a fixed amount over the contract service period and the related revenues are recognized on a straight-line basis over the term of the contract. For certain contracts where considerations are based on the usage of the Hosting services, the related revenues are recognized based on the consumption at the predetermined rate as the services are rendered throughout the contact term. The Company is a principal and records revenue for Hosting service on a gross basis. VPN services are services that the Company extends customers’ private networks by setting up secure and dedicated connections through the public internet. VPN services are provided to customers for a fixed amount over the contract service period and revenue are recognized on a straight-line basis over the term of the contract. The Company is a principal and records revenue for VPN service on a gross basis. The Company partners with Microsoft to provide Cloud services that allow enterprise and individual customers to run their applications over the internet using the IT infrastructure. Cloud services are generally charged by the Company to the end customers for a fixed amount or based on the actual usage of the cloud resources at predetermined rates over the subscription period, which in general is one year. The Company fulfils its performance obligation of facilitating Microsoft to provide the Cloud services to the end customers by providing, but not limited to, contract processing management, billing, payment collection, maintenance, help desk supports and certain IT infrastructure services. These are considered as a series of distinct services that are substantially the same and have the same pattern of transfer to the customer; therefore, they are accounted for as a single performance obligation that is satisfied over time. The corresponding consideration that the Company is entitled to is recognized as revenue using a time-based method since this best depicts the pattern of the control transfer. Revenue from Cloud services consists of monthly incentive revenues received from Microsoft upon completion of certain conditions and gross billing amount received from end customers net of considerations remitted by the Company to Microsoft. When the contract is modified to add distinct services to the single performance obligation for additional fees, such changes are accounted for prospectively as a termination of the old contract and the creation of a new contract. For certain arrangements, customers are required to pay the Company before the services are delivered. When either party to a revenue contract has performed, the Company recognizes a contract asset or a contract liability in the consolidated balance sheets, depending on the relationship between the Company’s performance and the customer’s payment. Contract liabilities were mainly related to fee received for Hosting services to be provided over the contract period, which were presented as deferred revenue on the consolidated balance sheets. Deferred revenue represented the Company’s obligation to transfer the goods or services to a customer for which the Company has received consideration (or an amount of consideration is due) from the customer. As of December 31, 2019 and 2020, the Company has deferred revenue amounting up to RMB57,625 and RMB63,245 (US$9,693), respectively. Revenue recognized from opening deferred revenue balance was RMB46,730 (US$7,162) for the year ended December 31, 2020. The Company’s certain Hosting service contains lease and non-lease components. The Company elected to adopt the practical expedient which allows lessors to combine lease and non-lease components and account for them as one component if 1) the timing and pattern of transfer of the lease component and non-lease component is the same; 2) the lease component should be classified as an operating lease if it were accounted for separately. The combined component is accounted for in accordance with the current lease accounting guidance (“ASC 842”) if the lease component is predominant, and in accordance with the ASC 606 if the non-lease component is predominant. The Company has determined that the non-lease component is the predominant component in Hosting service. Therefore, the Company has accounted for the combined component in accordance with ASC 606. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) (r) Revenue recognition (continued) The Company does not disclose the value of unsatisfied performance obligations as the Company’s revenue contracts are (i) contracts with an original expected length of one year or less or (ii) contracts for which the Company recognizes revenue at the amount to which it has the right to invoice for services performed.
Cost of revenues	(s) Cost of revenues Cost of revenues consists primarily of telecommunication costs, depreciation of the Company’s long-lived assets, amortization of acquired intangible assets, maintenance, data center rental expenses directly attributable to the provision of the IDC services, payroll and other related costs of operations.
Advertising expenditures	(t) Advertising expenditures Advertising expenditures are expensed as incurred and are included in sales and marketing expenses, which amounted to RMB7,968, RMB6,095 and RMB7,779 (US$1,192) for the years ended December 31, 2018, 2019 and 2020, respectively.
Research and development expenses	(u) Research and development expenses Research and development expenses consist primarily of payroll and related personnel costs for routine upgrades and related enhancements of the Company’s services and network. Research and development expenses are expensed as incurred except for costs to develop internal-use software or add significant upgrades and enhancements resulting in additional functionality to internal-use software that meet the capitalization criteria in accordance with ASC Subtopic 350-40, Intangibles-Goodwill and Other, Internal-Use Software
Government grants	(v) Government grants Government grants are provided by the relevant PRC municipal government authorities to subsidize the cost of certain research and development projects. The amount of such government grants is determined solely at the discretion of the relevant government authorities and there is no assurance that the Company will continue to receive these government grants in the future. Government grants are recognized when it is probable that the Company will comply with the conditions attached to them, and the grants are received. When the grant relates to an expense item, it is recognized in the consolidated statement of operations over the period necessary to match the grant on a systematic basis to the costs that it is intended to compensate, as a reduction of the related operating expense. When the grant relates to an asset, it is recognized as deferred government grants and released to the consolidated statement of operations in equal amounts over the expected useful life of the related asset, when operational, as a reduction of the related depreciation expense. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
Capitalized interest	(w) Capitalized interest Interest costs are capitalized if they are incurred during the acquisition, construction or production of a qualifying asset and such costs could have been avoided if expenditures for these assets have not been made. As a result of total interest costs capitalized during the period, the interest expense for the years ended December 31, 2018, 2019 and 2020, was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Interest expense and amortization cost of bonds payable 150,098 223,832 223,785 34,297 Interest expense on convertible promissory notes ​ — ​ — ​ 18,880 ​ 2,893 Interest expense on bank and other borrowings 19,395 14,212 39,424 6,042 Interest expense on finance leases 79,935 120,185 130,196 19,953 Total interest costs 249,428 358,229 412,285 63,185 Less: Total interest costs capitalized (13,362) (12,274) (31,676) (4,854) Interest expense, net 236,066 345,955 380,609 58,331
Income taxes	(x) Income taxes The Company accounts for income taxes using the liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and tax bases of assets and liabilities using enacted tax rates that will be in effect in the period in which the differences are expected to reverse. The carrying amount of deferred tax assets is reviewed on an entity-by-entity basis and is reduced by a valuation allowance to the extent that it is more-likely-than-not that the benefits of the deferred tax assets will not be realized in future years. The valuation allowance is determined based on the weight of positive and negative evidences including future reversals of existing taxable temporary differences, the adequacy of future taxable income exclusive of reversing temporary differences, and verifiable tax planning. The estimated future taxable income involves significant assumptions of forecasted revenue growth that take into consideration of the Company’s historical financial results, its plan of expanding operating capacity as well as current industry trends. The effect on deferred taxes of a change in tax rates is recognized in income in the period that includes the enactment date of the change in tax rate. All deferred income tax assets and liabilities are classified as non-current on the consolidated balance sheets. The Company applies ASC Topic 740, Accounting for Income Taxes The Company has elected to classify interest and penalties related to unrecognized tax benefits, if and when required, as part of “income tax expenses” in the consolidated statements of operations. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
Share-based compensation	(y) Share-based compensation Share options and Restricted Share Units (“RSUs”) granted to employees are accounted for under ASC Topic 718, Compensation—Stock Compensation The Company has elected to recognize compensation expenses using the straight-line method for share-based awards granted with service conditions that have a graded vesting schedule. For share-based awards granted with performance conditions, the Company recognizes compensation expenses using the accelerated method. The Company commences recognition of the related compensation expenses if it is probable that the defined performance condition will be met. To the extent that the Company determines that it is probable that a different number of share-based awards will vest depending on the outcome of the performance condition, the cumulative effect of the change in estimate is recognized in the period of change. For share-based awards with market conditions, the probability to achieve market conditions is reflected in the grant date fair value. The Company recognized the related compensation expenses when the requisite service is rendered using the accelerate method. On November 26, 2016, the Board approved a new incentive program to certain individuals with a new bonus scheme which will be settled by issuing a variable number of shares with a fair value equal to fixed dollar amount on the settlement date. The Company remeasures the fair value of such liability at each reporting period end through earnings until the actual settlement date, which is the date when the number of underlying shares were fixed and recorded the compensation cost over the remaining vesting term. A cancellation of the terms or conditions of an equity award under original award in exchange for a new award should be treated as modification. The compensation costs associated with the modified awards are recognized if either the original vesting conditions or the new vesting conditions have been achieved. Total recognized compensation cost for the awards is at least equal to the fair value of the original awards at the grant date unless at the date of the modification the performance or service conditions of the original awards are not expected to be satisfied. The incremental compensation cost is measured as the excess of the fair value of the replacement awards over the fair value of original awards at the modification date. Therefore, in relation to the modified awards, the Company recognizes share-based compensation over the vesting periods of the new awards, which comprises (i) the amortization of the incremental portion of share-based compensation over the remaining vesting term, and (ii) any unrecognized compensation cost of original awards, using either the original term or the new term, whichever results in higher expenses for each reporting period. For a modification of a market condition, the incremental portion of share-based compensation and unrecognized compensation cost of original award are recognized over new vesting period. For modification of a liability award that remains a liability after modification, the liability award continues to be remeasured at fair value at each reporting date. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
Loss per share	(z) Loss per share In accordance with ASC Topic 260, Earnings per Share
Share repurchase program	(aa) Share repurchase program Pursuant to the Board of Directors’ resolutions on December 2, 2019, the Company’s management is authorized to repurchase, in one or more tranches, up to an aggregate of US$20,000 of its own outstanding shares (including shares represented by ADSs) (each such transaction a “Repurchase”) over a period of 13 months ending on December 31, 2020. The Company accounted for the repurchased shares as Treasury Stock at cost in accordance to ASC Subtopic 505-30, Treasury Stock For the years ended December 31, 2018, 2019 and 2020, the Company repurchased nil, 242,830 and nil ADSs for a consideration of nil, RMB11,840 and nil, respectively.
Comprehensive loss	(bb) Comprehensive loss Comprehensive loss is defined as the decrease in equity of the Company during a period from transactions and other events and circumstances excluding transactions resulting from investments by owners and distributions to owners. Accumulated other comprehensive income of the Company includes only foreign currency translation adjustments related to the Company and its overseas subsidiaries, whose functional currency is US$. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
Segment reporting	(cc) Segment reporting In accordance with ASC Topic 280 , Segment Reporting (“ASC 280”), the Company had one reportable segment since the Company’s chief executive officer, who has been identified as the Company’s chief operating decision-maker (“CODM”) formerly relied on the results of operations of hosting and related services when making decisions on allocating resources and assessing performance of the Company, the Company has only one hosting and related services and the CODM reviews the operation result of the Company as a whole. Hosting and related services business focuses primarily on colocation, interconnectivity, cloud, VPN, hybrid IT and other value-added services. As of December 31, 2018, 2019 and 2020, the Company only had one reporting segment. Because substantially all of the Company’s long-lived assets and revenues are located in and derived from the PRC, geographical segments are not presented.
Employee benefits	(dd) Employee benefits The full-time employees of the Company’s PRC subsidiaries are entitled to staff welfare benefits including medical care, housing fund, pension benefits and unemployment insurance, which are governmental mandated defined contribution plans. These entities are required to accrue for these benefits based on certain percentages of the employees’ respective salaries, subject to certain ceilings, in accordance with the relevant PRC regulations, and make cash contributions to the state-sponsored plans out of the amounts accrued.
Comparatives	(ee) Comparatives Certain items reported in the prior year’s consolidated financial statements have been reclassified to conform with the current year’s presentation.
Recent accounting pronouncements	(ff) Recent accounting pronouncements In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform In August 2020, the FASB issued ASU No. 2020-06, Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity

ORGANIZATION (Tables)

ORGANIZATION (Tables)	12 Months Ended
	Dec. 31, 2020
ORGANIZATION
Schedule of significant subsidiaries of the Company, VIEs and subsidiaries of VIEs	(a) As of December 31, 2020, the significant subsidiaries of the Company and consolidated variable interest entities are as follows: ​ Entity Date of Place of Percentage Principal activities ​ ​ ​ Direct ​ Variable Interest Entities (the “VIEs”): ​ ​ ​ ​ Beijing Yiyun Network Technology Co., Ltd. (“21Vianet Technology”) (1) / (2) ​ October 22, 2002 ​ PRC ​ — ​ Provision of internet data center services Beijing iJoy Information Technology Co., Ltd. (“BJ iJoy”) (1) / (2) ​ April 30, 2013 ​ PRC ​ — ​ Provision of internet data center, content delivery network services WiFire Network Technology (Beijing) Co., Ltd. (“WiFire Network”) (1) / (2) ​ April 1, 2014 ​ PRC ​ — ​ Provision of telecommunication services Shanghai Zhiyan Yunwei Technology Co.,Ltd. (“SH Zhiyan”) (1) / (2) ​ December 12, 2020 ​ PRC ​ — ​ Provision of telecommunication services ​ ​ ​ ​ ​ ​ ​ ​ ​ Held directly by 21Vianet Technology: ​ ​ ​ ​ Beijing 21Vianet Broad Band Data Center Co., Ltd. (“21Vianet Beijing”) (1) / (2) ​ March 15, 2006 ​ PRC ​ — ​ Provision of internet data center services ​ ​ ​ ​ ​ ​ ​ ​ ​ Held directly by 21Vianet Beijing: ​ ​ ​ ​ 21Vianet (Xi’an) Information Outsourcing Industry Park Services Co., Ltd. (“Xi’an Sub”) (1) / (2) ​ June 23, 2008 ​ PRC ​ — ​ Provision of internet data center services Langfang Xunchi Computer Data Processing Co., Ltd. (“LF Xunchi”) (1) / (2) ​ December 19, 2011 ​ PRC ​ — ​ Dormant company Beijing Yilong Xinda Technology Co., Ltd. (“Yilong Xinda”) (1) / (2) ​ August 6, 2010 ​ PRC ​ — ​ Provision of internet data center services Beijing Yichengtaihe Investment Co., Ltd. (“BJ Yichengtaihe”) (1) / (2) ​ September 30, 2014 ​ PRC ​ — ​ Provision of internet data center services Guangzhou Lianyun Big Data Co. Ltd. (“GZ Lianyun”) (1) / (2) ​ April 14, 2016 ​ PRC ​ — ​ Provision of internet data center services Beijing Xianghu Yunlian Technology Co., Ltd. (“Xianghu Yunlian”) (1) / (2) ​ November 7, 2018 ​ PRC ​ — ​ Provision of internet data center services Shanghai Hujiang Songlian Technology Co., Ltd. (“Hujiang Songlian”) (1) / (2) ​ December 17, 2018 ​ PRC ​ — ​ Provision of internet data center services Beijing Shuhai Hulian Technology Co., Ltd. (“BJ Shuhai”) (1) / (2) ​ January 2, 2019 ​ PRC ​ — ​ Provision of internet data center services Nantong Chenghong Cloud Computing Co., Ltd. (“NT Chenghong”) (1) / (2) ​ December 24, 2019 ​ PRC ​ — ​ Provision of internet data center services Shanghai Shuzhong Investment Management Co., Ltd. (“SH Shuzhong”) (1)/(2)/(5) ​ June 30, 2020 ​ PRC ​ — ​ Provision of internet data center services Sanhe Shulifang Information Technology Co., Ltd. (“Shulifang”) (1)/(2)/(6) ​ July 21, 2020 ​ PRC ​ — ​ Provision of internet data center services Langfang Huahai Internet Technology Co., Ltd. (“LF Huahai”) (1)/(2)/(7) ​ September 11, 2020 ​ PRC ​ — ​ Provision of internet data center services ​ Entity Date of Place of Percentage Principal activities ​ ​ ​ ​ Held directly by SH Zhiyan: ​ ​ ​ ​ Shanghai Blue Cloud Technology Co., Ltd. (“SH Blue Cloud”) (1) / (2) ​ March 21, 2013 ​ PRC ​ — Provision of Office 365 and Windows Azure platform services ​ ​ ​ ​ ​ ​ ​ ​ ​ Held directly by DYX and LF Xunchi: ​ ​ ​ ​ ​ ​ ​ ​ Shenzhen Diyixian Telecommunication Co., Ltd. (“SZ DYX”) (1) ​ August 10, 2014 ​ PRC ​ 100 % Provision of virtual private network services ​ (1) Collectively, the “PRC Subsidiaries”. (2) Collectively, the “Consolidated VIEs”. (3) On August 10, 2014, the Company and its subsidiary, LF Xunchi, acquired 100% equity interest of Dermot BVI and its subsidiaries (collectively referred to as “Dermot Entities”). (4) On August 20, 2019, the Company through its subsidiary, DRP Investment, became the sole shareholder in Shihua Holding 2 and its subsidiaries (Note 4). (5) On June 30, 2020, the Company through its subsidiary, Shanghai Shilian Technology Co., Ltd (“SH Shilian”), acquired 100% equity interest of SH Shuzhong (Note 4). (6) On July 21, 2020, the Company through its subsidiary, SH Shilian, acquired 100% equity interest of Shulifang (Note 4). (7) On September 11, 2020, the Company through its subsidiaries, SH Shilian and 21Vianet Venus International Investment Limited (“21Vianet Venus”), acquired 100% equity interest of LF Huahai (Note 4). (8) On November 17, 2020, the Company through its subsidiary, 21Vianet Saturn International Investment Limited (“21Vianet Saturn”) and Beijing Zhongshun Yongfeng Investment Consulting Co.,Ltd. (“YF WFOE”), acquired 100% equity interest of BJ JHC and BJ ST (Note 4).
Schedule of consolidated VIE before eliminating intercompany balances	The following tables represent the financial information of the Consolidated VIEs as of December 31, 2019 and 2020 and for the years ended December 31, 2018, 2019 and 2020 before eliminating the intercompany balances and transactions between the Consolidated VIEs and other entities within the Company: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ ASSETS ​ ​ ​ ​ ​ ​ Current assets: Cash and cash equivalents 591,503 737,556 113,035 Restricted cash 260,961 260,450 39,916 Accounts receivable (net of allowance for doubtful debt of RMB66,416 and RMB67,632 (US$10,365) as of December 31, 2019 and 2020, respectively) 513,440 664,610 101,856 Prepaid expenses and other current assets 1,371,564 1,622,662 248,684 Amounts due from related parties 57,982 12,968 1,987 Total current assets 2,795,450 3,298,246 505,478 Non-current assets: ​ ​ Property and equipment, net 3,580,341 5,170,878 792,472 Intangible assets, net 151,722 342,288 52,458 Land use rights, net 58,588 46,719 7,160 Operating lease right-of-use assets, net ​ 1,144,846 ​ 1,134,073 ​ 173,804 Goodwill 302,647 308,110 47,220 Restricted cash 66,119 27,719 4,248 Deferred tax assets, net 180,959 168,181 25,775 Amounts due from related parties 20,654 20,562 3,151 Other non-current assets 262,685 435,144 66,689 Long-term investments, net 189,571 172,593 26,451 Total non-current assets 5,958,132 7,826,267 1,199,428 Total assets 8,753,582 11,124,513 1,704,906 Current liabilities: ​ ​ Short-term bank borrowings 232,323 34,000 5,211 Accounts payable and notes payable 211,710 182,669 27,995 Accrued expenses and other payables 622,160 981,961 150,492 Advance from customers 1,068,692 1,041,594 159,631 Deferred revenue 52,088 58,066 8,899 Income tax payable 8,175 12,743 1,953 Amounts due to inter-companies (1) 2,786,838 4,248,422 651,099 Amounts due to related parties 56,977 50,193 7,692 Current portion of finance lease liabilities 220,363 362,760 55,595 Current portion of long-term borrowings 32,500 165,328 25,338 Current portion of deferred government grant 2,595 2,074 318 Current portion of operating lease liabilities ​ 410,422 ​ 427,114 ​ 65,458 Total current liabilities 5,704,843 7,566,924 1,159,681 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Non-current liabilities: ​ ​ ​ ​ ​ ​ Amounts due to inter-companies (1) 1,020,972 1,020,972 156,471 Amounts due to related parties 745,899 747,746 114,597 Long-term borrowings 79,500 570,135 87,377 Non-current portion of finance lease liabilities 549,669 299,399 45,885 Unrecognized tax benefits 1,991 68,317 10,470 Deferred tax liabilities 82,725 155,281 23,798 Non-current portion of deferred government grant 5,906 4,100 628 Non-current portion of operating lease liabilities ​ 529,546 ​ 497,268 ​ 76,210 Total non-current liabilities 3,016,208 3,363,218 515,436 Total liabilities 8,721,051 10,930,142 1,675,117 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Net revenues 2,532,854 2,858,176 3,885,141 595,424 Net profit 52,986 111,592 73,748 11,302 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Net cash generated from operating activities 693,620 495,308 748,418 114,700 Net cash generated from (used in) investing activities 132,522 (1,247,764) (1,943,358) (297,833) Net cash (used in) generated from financing activities (423,467) 885,286 1,302,082 199,553 Net increase in cash and cash equivalents and restricted cash 402,705 132,830 107,142 16,420 ​ (1) Amounts due to inter-companies consist of intercompany payables to the other companies within the Company for the purchase of telecommunication resources and property and equipment on behalf of the Consolidated VIEs.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2020
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Schedule of property and equipment are depreciated using the straight-line method over the estimated useful lives of the assets	​ ​ ​ ​ Category Estimated useful life Property 25-46 years Leasehold improvements Over the shorter of lease term or the estimated useful lives of the assets Optical fibers 10-20 years Computer and network equipment 1-10 years Office equipment 2-8 years Motor vehicles 2-8 years ​
Schedule of weighted average useful lives of intangible assets	​ ​ ​ ​ Purchased software 5.1 years Radio spectrum license 15 years Operating permits* ​ 29.3 years Contract backlog* 4.9 years Customer relationships* 8.8 years Licenses* 15 years Supplier relationships* 10 years Trade Names* 20 years Platform software* 5 years Non-complete agreements* 5 years Internal use software 3.8 years Customer contract* ​ 6.5 years ​ * Acquired in the acquisitions of subsidiaries. ​ 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
Schedule of impairment charges associated with long-lived assets and acquired intangibles	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Impairment of equipment — — 35,793 5,486 Impairment of intangible assets — — 38,654 5,924 Impairment of other non-current assets — — 7,172 1,099
Schedule of total interest expenses capitalized during the period, the interest expenses	As a result of total interest costs capitalized during the period, the interest expense for the years ended December 31, 2018, 2019 and 2020, was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Interest expense and amortization cost of bonds payable 150,098 223,832 223,785 34,297 Interest expense on convertible promissory notes ​ — ​ — ​ 18,880 ​ 2,893 Interest expense on bank and other borrowings 19,395 14,212 39,424 6,042 Interest expense on finance leases 79,935 120,185 130,196 19,953 Total interest costs 249,428 358,229 412,285 63,185 Less: Total interest costs capitalized (13,362) (12,274) (31,676) (4,854) Interest expense, net 236,066 345,955 380,609 58,331

ACQUISITION AND DISPOSAL OF S_2

ACQUISITION AND DISPOSAL OF SUBSIDIARIES (Tables)	12 Months Ended
	Dec. 31, 2020
Jiangheyun
Business Acquisition [Line Items]
Schedule of net identifiable assets of acquiree	​ ​ ​ ​ ​ ​ ​ RMB US$ Net assets acquired: ​ ​ Property and equipment, net 279,556 42,843 Operating permits (Note 9) 110,418 16,922 Customer contract (Note 9) 33,208 5,089 Operating lease right-of-use assets, net 112,398 17,226 Deferred tax assets 3,150 483 Other non-current assets 4,428 678 Cash and cash equivalents 30,319 4,647 Other current assets 8,833 1,354 Other current liabilities (90,805) (13,916) Operating lease liabilities (120,120) (18,409) Finance lease liabilities (84,082) (12,886) Deferred tax liabilities (55,288) (8,473) Total consideration in cash 232,015 35,558
SH Shuzhong
Business Acquisition [Line Items]
Schedule of net identifiable assets of acquiree	​ ​ ​ ​ ​ ​ ​ RMB US$ Property and equipment, net 348,475 53,406 Operating lease right-of-use assets, net 81,034 12,419 Customer contract (Note 9) 33,500 5,134 Purchased software 23 4 Deferred tax assets 14,848 2,275 Other non-current assets 1,685 258 Other current assets 44,774 6,862 Total assets acquired 524,339 80,358 Other current liabilities (406,932) (62,365) Operating lease liabilities (45,034) (6,902) Deferred tax liabilities (41,169) (6,309) Total liabilities assumed (493,135) (75,576) Net assets acquired 31,204 4,782 Purchase consideration 36,667 5,619 Goodwill 5,463 837
Shulifang
Business Acquisition [Line Items]
Schedule of net identifiable assets of acquiree	​ ​ ​ ​ ​ ​ ​ RMB US$ Net assets acquired: ​ ​ Operating permits (Note 9) 45,134 6,917 Operating lease right-of-use assets, net 15,206 2,330 Other non-current assets 15,409 2,362 Cash and cash equivalents 53 8 Other current assets 601 91 Operating lease liabilities (15,206) (2,330) Other current liabilities (16,913) (2,592) Deferred tax liabilities (11,284) (1,729) Total consideration in cash 33,000 5,057
LF Huahai
Business Acquisition [Line Items]
Schedule of net identifiable assets of acquiree	​ ​ ​ ​ ​ ​ ​ RMB US$ Net assets acquired: ​ ​ Operating permits (Note 9) 119,352 18,291 Operating lease right-of-use assets, net 183,174 28,073 Other non-current assets 27,524 4,218 Cash and cash equivalents 173 27 Other current assets 4,088 627 Other current liabilities (35,600) (5,456) Operating lease liabilities (183,873) (28,180) Deferred tax liabilities (29,838) (4,573) Total consideration in cash 85,000 13,027
Beijing Shuhai Data Technology Co., Ltd ("BJ Shuhai")
Business Acquisition [Line Items]
Schedule of net identifiable assets of acquiree	​ ​ ​ ​ ​ RMB Net assets acquired: Operating permits (Note 9) 100,380 Cash and cash equivalents 59 Other current assets 9,625 Right-of-use assets 129,937 Other current liabilities (16,714) Lease liabilities (129,937) Deferred tax liabilities (25,095) Total consideration in cash 68,255
Shihua DC Investment Holdings 2 Limited ("Shihua Holdings 2")
Business Acquisition [Line Items]
Schedule of net identifiable assets of acquiree	​ ​ ​ ​ ​ RMB Net assets acquired: Property and land use right 150,880 Construction-in-progress 465 Cash and cash equivalents 67,563 Other current assets 1,333,329 Other current liabilities (1,203,894) Deferred tax liabilities (33,096) Total consideration* 315,247 ​ * Consideration transferred is the carrying amount of the previously held 49% of equity interest. 4. ACQUISITION AND DISPOSAL OF SUBSIDIARIES (CONTINUED) Acquisition in 2019 (continued)
Nantong Chenghong Cloud Computing Co., Ltd. ("NT Chenghong")
Business Acquisition [Line Items]
Schedule of net identifiable assets of acquiree	​ ​ ​ ​ ​ RMB Net assets acquired: Construction-in-progress 158,471 Equipment 13 Cash and cash equivalents 129 Other current assets 11,840 Other current liabilities (88,830) Deferred tax liabilities (1,623) Total consideration in cash 80,000 ​

ACCOUNTS AND NOTES RECEIVABLE_2

ACCOUNTS AND NOTES RECEIVABLE, NET (Tables)	12 Months Ended
	Dec. 31, 2020
ACCOUNTS AND NOTES RECEIVABLE, NET
Schedule of accounts and notes receivable and the allowance for doubtful debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Accounts receivable 722,840 913,902 140,062 Notes receivable 2,146 2,252 345 Allowance for doubtful debt (67,828) (68,921) (10,563) ​ 657,158 847,233 129,844
Schedule of analysis of the allowance for doubtful debt	As of December 31, 2019 and 2020, all accounts and notes receivable were due from third party customers. An analysis of the allowance for doubtful debt was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Balance at beginning of the year 70,970 67,828 10,395 Cumulative adjustment for changes in accounting policy ​ — ​ 2,740 ​ 420 Additional provision charged to expense 485 2,393 367 Write-off of accounts receivable (3,627) (4,040) (619) Balance at the end of the year 67,828 68,921 10,563

SHORT-TERM INVESTMENTS (Tables)

SHORT-TERM INVESTMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
SHORT-TERM INVESTMENTS
Schedule of short-term investments	Short-term investments consisted of the following as of December 31, 2019 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Time deposits 363,856 285,872 43,812 ​

PREPAID EXPENSES AND OTHER CU_2

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Tables)	12 Months Ended
	Dec. 31, 2020
PREPAID EXPENSES AND OTHER CURRENT ASSETS
Schedule of prepaid expenses and other current assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Prepaid expenses 878,155 884,156 135,503 Tax recoverables ​ 570,913 ​ 879,237 ​ 134,749 Deposits 17,391 31,774 4,870 Loan to third parties 73,557 19,107 2,928 Interest receivables 14,359 1,484 227 Staff advances 1,866 968 148 Others 61,908 49,458 7,580 ​ 1,618,149 1,866,184 286,005

PROPERTY AND EQUIPMENT, NET (Ta

PROPERTY AND EQUIPMENT, NET (Tables)	12 Months Ended
	Dec. 31, 2020
PROPERTY AND EQUIPMENT, NET
Schedule of property and equipment, including those held under finance leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ At cost: ​ ​ ​ ​ ​ ​ Property 899,609 1,511,429 231,637 Leasehold improvements 1,458,749 2,609,828 399,974 Computer and network equipment 3,539,709 4,899,577 750,893 Optical fibers 142,723 142,723 21,873 Office equipment 22,102 26,845 4,114 Motor vehicles 2,308 2,668 409 ​ 6,065,200 9,193,070 1,408,900 Less: Accumulated depreciation (2,514,800) (3,285,138) (503,469) Impairment ​ — ​ (35,793) ​ (5,486) ​ 3,550,400 5,872,139 899,945 Construction-in-progress 1,893,165 2,234,286 342,419 ​ 5,443,565 8,106,425 1,242,364
Schedule of depreciation expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Cost of revenues 520,791 644,108 850,746 130,382 Sales and marketing expenses 986 2,107 2,399 368 General and administrative expenses 28,727 30,110 29,711 4,553 Research and development expenses 15,987 20,203 25,531 3,913 ​ 566,491 696,528 908,387 139,216
Schedule of carrying amounts of the Company's property and equipment held under finance leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Property 365,353 921,970 141,298 Computer and network equipment 639,311 1,019,588 156,259 Optical fibers 142,723 137,924 21,138 ​ 1,147,387 2,079,482 318,695 Less: Accumulated depreciation (408,196) (661,796) (101,425) ​ 739,191 1,417,686 217,270 Construction-in-progress 659,014 92,545 14,183 ​ 1,398,205 1,510,231 231,453 ​
Schedule of carrying amounts of property and equipment pledged by the Company to secure banking borrowings	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Property 137,585 264,784 40,580 Leasehold improvements ​ 66,162 ​ 90,947 ​ 13,938 Computer and network equipment ​ — ​ 40,871 ​ 6,264 Construction-in-progress — 238,771 36,593

INTANGIBLE ASSETS, NET (Tables)

INTANGIBLE ASSETS, NET (Tables)	12 Months Ended
	Dec. 31, 2020
INTANGIBLE ASSETS, NET
Schedule of intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Radio ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Internal ​ ​ ​ ​ Purchased ​ spectrum ​ Operating ​ Contract ​ Customer ​ ​ ​ Supplier ​ Trade ​ Customer ​ Non-compete ​ use ​ ​ ​ ​ software ​ license ​ Permits ​ backlog ​ relationships ​ Licenses ​ relationships ​ names ​ contract ​ agreements ​ software ​ Total ​ RMB RMB RMB RMB RMB RMB RMB RMB RMB RMB RMB RMB Intangible assets, net January 1, 2019 47,254 72,908 — 5,162 112,961 3,883 17,070 90,591 — 44 5,440 355,313 Additions 11,128 — 100,380 — — — — — — — 13,189 124,697 Foreign currency translation difference 413 1,200 — — — — — — — — — 1,613 Amortization expense (16,068) (8,985) (3,136) (5,162) (24,921) (385) (3,074) (5,813) — (44) (3,440) (71,028) Intangible assets, net December 31, 2019 42,727 65,123 97,244 — 88,040 3,498 13,996 84,778 — — 15,189 410,595 Additions 12,893 ​ — 274,904 — — — — — 66,708 — 8,684 363,189 Foreign currency translation difference (32) (4,213) — — — — — — — — — (4,245) Amortization expense (13,689) (8,403) (5,189) — (24,854) (385) (3,074) (5,813) (3,602) — (7,681) (72,690) Impairment ​ — ​ (38,654) ​ — ​ — ​ — ​ — ​ — ​ — ​ — ​ — ​ — ​ (38,654) Intangible assets, net December 31, 2020 41,899 13,853 366,959 — 63,186 3,113 10,922 78,965 63,106 — 16,192 658,195 Intangible assets, net December 31, 2020 (US$) 6,421 2,123 56,239 — 9,684 477 1,674 12,102 9,671 — 2,482 100,873 ​
Schedule of annual estimated amortization expenses of intangible assets	​ ​ ​ ​ ​ ​ ​ RMB US$ 2021 78,149 11,977 2022 63,039 9,661 2023 41,574 6,371 2024 31,923 4,892 2025 27,424 4,203 ​ 242,109 37,104

LAND USE RIGHTS, NET (Tables)

LAND USE RIGHTS, NET (Tables)	12 Months Ended
	Dec. 31, 2020
LAND USE RIGHTS, NET
Land use rights	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Cost 249,804 278,138 42,627 Accumulated amortization (16,650) (22,765) (3,489) Land use rights, net 233,154 255,373 39,138 ​
Carrying value of land use rights pledged by company to secure banking borrowings	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Land use rights 15,989 141,000 21,609

GOODWILL (Tables)

GOODWILL (Tables)	12 Months Ended
	Dec. 31, 2020
GOODWILL
Schedule of changes in the carrying amount of goodwill	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Balance as of January 1 989,530 989,530 151,652 Additions ​ — ​ 5,463 ​ 837 Balance as of December 31 989,530 994,993 152,489 ​

LONG-TERM INVESTMENTS, NET (Tab

LONG-TERM INVESTMENTS, NET (Tables)	12 Months Ended
	Dec. 31, 2020
LONG-TERM INVESTMENTS, NET
Schedule of long-term investments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Equity investments without readily determinable fair values 43,824 17,137 2,626 Equity method investments 124,116 116,667 17,880 Available-for-sale debt investments 1,713 1,713 263 ​ 169,653 135,517 20,769 ​
Schedule of equity method investments	Equity method investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Increase (decrease) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ during ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the year ended ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2018 ​ December 31, 2019 ​ As of December 31, 2019 ​ ​ ​ ​ Share ​ Investments ​ ​ ​ Share ​ Distribution/derecognize ​ ​ ​ Share ​ Investments ​ ​ Cost of ​ equity ​ in equity ​ Cost of ​ equity gain ​ of share ​ Cost of ​ equity gain ​ in equity ​ investments gain (loss) investee investments (loss) equity (gain) loss investments (loss) investee ​ RMB RMB ​ RMB RMB RMB ​ RMB RMB RMB ​ RMB Yizhuang Fund 101,000 25,681 ​ 126,681 — ​ 1,671 ​ (20,200) ​ 101,000 ​ 7,152 ​ 108,152 Shihua DC Holdings 366,623 (33,658) ​ 332,965 (337,555) ​ (17,718) ​ 22,308 ​ 29,068 ​ (29,068) ​ — Jingliang Inter Cloud ​ 6,000 (34) ​ 5,966 — ​ (1,894) ​ — ​ 6,000 ​ (1,928) ​ 4,072 Jingliang Century Cloud ​ 4,000 — ​ 4,000 — ​ — ​ — ​ 4,000 ​ — ​ 4,000 Huaye Cloud ​ 23,333 (6,319) ​ 17,014 (23,333) ​ (11,534) ​ 17,853 ​ — ​ — ​ — ZJK Energy ​ 5,907 (2,157) ​ 3,750 — ​ 212 ​ — ​ 5,907 ​ (1,945) ​ 3,962 WiFire Entities 15,000 (15,000) ​ — 5,000 ​ (5,000) ​ — ​ 20,000 ​ (20,000) ​ — Qidi Chengxin ​ — ​ — ​ — ​ 3,930 ​ — ​ — ​ 3,930 ​ — ​ 3,930 ​ 521,863 (31,487) ​ 490,376 (351,958) ​ (34,263) ​ 19,961 ​ 169,905 ​ (45,789) ​ 124,116 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Increase (decrease) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ during ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the year ended ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2019 ​ December 31, 2020 ​ As of December 31, 2020 ​ ​ ​ ​ Share ​ Investments ​ ​ ​ Share ​ Distribution/derecognize ​ ​ ​ Share ​ Investments ​ Investments ​ ​ Cost of ​ equity ​ in equity ​ Cost of ​ equity gain ​ of share ​ Cost of ​ equity gain ​ in equity ​ in equity ​ investments gain (loss) investee investments (loss) equity (gain) loss investments (loss) investee investee ​ RMB RMB ​ RMB ​ RMB ​ RMB ​ RMB ​ RMB ​ RMB ​ RMB ​ US$ Yizhuang Fund 101,000 ​ 7,152 ​ 108,152 ​ — ​ 12,254 ​ (17,723) ​ 101,000 ​ 1,683 ​ 102,683 ​ 15,737 Shihua DC Holdings 29,068 ​ (29,068) ​ — ​ (29,068) ​ — ​ 29,068 ​ — ​ — ​ — ​ — Jingliang Inter Cloud 6,000 ​ (1,928) ​ 4,072 ​ — ​ (903) ​ — ​ 6,000 ​ (2,831) ​ 3,169 ​ 486 Jingliang Century Cloud 4,000 ​ — ​ 4,000 ​ — ​ — ​ — ​ 4,000 ​ — ​ 4,000 ​ 613 ZJK Energy 5,907 ​ (1,945) ​ 3,962 ​ — ​ (803) ​ — ​ 5,907 ​ (2,748) ​ 3,159 ​ 484 WiFire Entities 20,000 ​ (20,000) ​ — ​ — ​ — ​ — ​ 20,000 ​ (20,000) ​ — ​ — Qidi Chengxin ​ 3,930 ​ — ​ 3,930 ​ — ​ (274) ​ — ​ 3,930 ​ (274) ​ 3,656 ​ 560 ​ 169,905 ​ (45,789) ​ 124,116 ​ (29,068) ​ 10,274 ​ 11,345 ​ 140,837 ​ (24,170) ​ 116,667 ​ 17,880

BORROWINGS (Tables)

BORROWINGS (Tables)	12 Months Ended
	Dec. 31, 2020
BORROWINGS
Schedule of borrowings and thier securities	Borrowings were as follows as of the respective balance sheet dates: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Short-term bank borrowings 234,500 34,000 5,211 Long-term bank borrowings, current portion 32,500 68,500 10,498 Other long-term borrowings, current portion ​ — ​ 111,828 ​ 17,138 ​ 267,000 214,328 32,847 Long-term bank borrowings, non-current portion 79,500 605,119 92,738 Other long-term borrowings, non-current portion ​ — ​ 281,877 ​ 43,200 Total borrowings 346,500 1,101,324 168,785 ​ Borrowings as of December 31, 2019 and 2020 were secured by the following: ​ December 31, 2019 ​ ​ ​ ​ Short-term bank borrowings Secured by (RMB) 34,500 ​ Unsecured borrowings. ​ ​ ​ 200,000 ​ Secured by restricted cash of RMB215,816. 234,500 ​ ​ ​ ​ ​ Long-term bank borrowings (including current portion) Secured by (RMB) 112,000 Secured by a subsidiary’s fixed assets and land-use right with net book value of RMB203,747 and RMB15,989, respectively (Note 8/Note 10). 112,000 ​ ​ ​ 13. BORROWINGS (CONTINUED) December 31, 2020 ​ ​ ​ Short-term bank borrowings Secured by (RMB) 34,000 ​ Unsecured borrowings. ​ ​ ​ 34,000 ​ ​ ​ ​ ​ Long-term borrowings (including current portion) Secured by (RMB) 404,781 Secured by subsidiary’s property and equipment and land-use right with net book value of RMB505,004 (US$77,395) and RMB40,034 (US$6,135), respectively (Note 8/Note 10). 271,861 ​ Secured by a subsidiary’s property and equipment and land-use right with net book value of RMB130,369 (US$19,980) and RMB100,966 (US$15,474), respectively (Note 8/Note 10), and a subsidiary’s stock. 190,682 ​ Unsecured borrowing. 100,000 ​ Secured by a subsidiary’s stock and the restricted cash of RMB104,400 (US$16,000). 100,000 Secured by a subsidiary’s stock. 1,067,324 ​ ​

ACCRUED EXPENSES AND OTHER PA_2

ACCRUED EXPENSES AND OTHER PAYABLES (Tables)	12 Months Ended
	Dec. 31, 2020
ACCRUED EXPENSES AND OTHER PAYABLES
Schedule of components of accrued expenses and other payables	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Payables for purchase of property, equipment and software 554,693 1,148,742 176,052 Payroll and welfare payables 179,195 204,732 31,377 Amounts due to the original shareholders for acquired entities * — 66,466 10,186 Payables for acquisitions 47,805 47,805 7,326 Accrued service fees 52,746 47,572 7,291 Payables for office supplies and utilities 24,562 38,485 5,898 Interest payables 58,961 37,799 5,793 Value-added tax and other taxes payable 14,523 10,473 1,605 Others 46,450 29,489 4,520 ​ 978,935 1,631,563 250,048 ​ * This represented the balance of unpaid cash consideration and the payables in other current liabilities due to original shareholders related to the acquisition of SH Shuzhong and LF Huahai (Note 4).

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2020
LEASES
Schedule of weighted-average remaining lease term and weighted-average discount rate	​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2019 2020 Weighted average remaining lease term: ​ ​ ​ ​ ​ Operating lease 9.4 years 12.2 years ​ Finance lease 15.3 years 14.6 years ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate: ​ Operating lease 6.09 % 6.56 % Finance lease 8.43 % 8.63 %
Schedule of total lease cost	​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2019 2020 Weighted average remaining lease term: ​ ​ ​ ​ ​ Operating lease 9.4 years 12.2 years ​ Finance lease 15.3 years 14.6 years ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate: ​ Operating lease 6.09 % 6.56 % Finance lease 8.43 % 8.63 %
Schedule of supplemental cash flow information related to leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ ​ Operating cash payments for operating leases 193,174 477,189 73,132 Financing cash payments for finance leases 333,614 376,232 57,660
Schedule of future lease payments under operating leases and finance leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Leases ​ Finance Leases ​ RMB US$ RMB US$ 2021 415,892 ​ 63,738 ​ 542,268 83,106 2022 221,680 ​ 33,974 ​ 293,643 45,003 2023 146,115 ​ 22,393 ​ 195,320 29,934 2024 103,891 ​ 15,922 ​ 124,389 19,063 2025 ​ 70,494 ​ 10,804 ​ 95,054 ​ 14,568 2026 and thereafter 1,115,382 ​ 170,940 ​ 1,678,170 257,191 Total future lease payments 2,073,454 ​ 317,771 ​ 2,928,844 448,865 Less: Imputed interest (728,543) ​ (111,654) ​ (1,286,619) (197,183) Present value of future lease payments * 1,344,911 ​ 206,117 ​ 1,642,225 251,682 ​ * Present value of future operating lease payments consisted of current portion of operating lease liabilities, non-current portion of operating lease liabilities and operating lease liabilities in amounts due to related parties, amounting to RMB452,272 (US$69,314), RMB645,499 (US$98,927) and RMB247,140 (US$37,876) for the year ended December 31, 2020, respectively.

BONDS PAYABLE (Tables)

BONDS PAYABLE (Tables)	12 Months Ended
	Dec. 31, 2020
BONDS PAYABLE
Schedule of repayments of the principal amounts of the Company's long-term borrowings, including the bonds payable, bank and other borrowings	​ ​ ​ ​ ​ ​ ​ RMB US$ For the years ending December 31, ​ ​ ​ ​ 2021 2,158,266 ​ 330,769 2022 222,796 ​ 34,145 2023 152,544 ​ 23,378 2024 189,988 ​ 29,117 2025 ​ 125,244 ​ 19,194 2026 and thereafter 222,119 ​ 34,041

DEFERRED GOVERNMENT GRANTS (Tab

DEFERRED GOVERNMENT GRANTS (Tables)	12 Months Ended
	Dec. 31, 2020
DEFERRED GOVERNMENT GRANTS
Schedule of movements of deferred government grants	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Balance at beginning of the year 22,435 15,792 8,501 1,303 Additions 500 — — — Recognized as a reduction of depreciation expense (7,143) (7,291) (2,327) (357) Balance at end of the year 15,792 8,501 6,174 946

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (Tables)	12 Months Ended
	Dec. 31, 2020
ACCUMULATED OTHER COMPREHENSIVE INCOME
Schedule of changes in accumulated other comprehensive income by component, net of tax of nil	​ ​ ​ ​ ​ ​ Foreign currency ​ ​ translation ​ RMB Balance as of January 1, 2018 (2,673) Current year other comprehensive income 88,652 Balance as of December 31, 2018 85,979 Current year other comprehensive loss (8,075) Balance as of December 31, 2019 77,904 Current year other comprehensive loss (133,439) Balance as of December 31, 2020 (55,535) Balance as of December 31, 2020, in US$ (8,511)

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2020
SHARE-BASED COMPENSATION
Schedule of employee share option activity under the 2010 Plan	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ average ​ ​ ​ ​ ​ ​ average ​ remaining ​ Aggregate ​ ​ Number of ​ exercise ​ contractual ​ intrinsic ​ ​ options ​ price ​ term ​ value ​ ​ (US$) (Years) (US$) Outstanding, January 1, 2020 1,445,345 0.51 1.3 — Exercised (459,168) 0.69 ​ ​ Forfeited ​ (477,311) ​ 0.53 ​ ​ ​ ​ Outstanding, December 31, 2020 508,866 0.33 0.8 2,774 Vested and expected to vest at December 31, 2020 508,866 0.33 0.8 2,774 Exercisable as of December 31, 2020 508,866 0.33 0.8 2,774 ​
Schedule of RSUs activity under the 2014 Plan	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Weighted ​ ​ ​ ​ ​ average ​ average ​ Aggregate ​ ​ Number of ​ grant date ​ remaining ​ intrinsic ​ ​ RSUs ​ fair value ​ contractual life ​ value ​ ​ (US$) (Years) (US$) Unvested, January 1, 2020 ​ 2,696,129 ​ 6.83 ​ 7.8 ​ ​ Granted 2,163,543 22.62 ​ ​ Vested (433,905) 8.91 ​ ​ Forfeited (333,310) 6.59 ​ ​ Unvested, December 31, 2020 4,092,457 14.95 8.2 141,967
Schedule of total share-based compensation expenses relating to share options and RSUs granted to employees	Total share-based compensation expenses relating to share options and RSUs granted to employees recognized for the years ended December 31, 2018, 2019 and 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Cost of revenues 2,668 1,884 15,251 2,337 Sales and marketing expenses 2,139 354 38,247 5,862 General and administrative expenses 53,346 40,501 82,672 12,670 Research and development expenses 1,385 1,177 634 97 ​ 59,538 43,916 136,804 20,966

TAXATION (Tables)

TAXATION (Tables)	12 Months Ended
	Dec. 31, 2020
TAXATION
Schedule of loss before income taxes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2018 2019 2020 ​ RMB RMB RMB US$ Non-PRC (214,063) (178,762) (2,708,101) (415,033) PRC 51,738 2,953 137,178 21,023 ​ (162,325) (175,809) (2,570,923) (394,010) ​
Schedule of income tax expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2018 2019 2020 ​ RMB RMB RMB US$ Current (44,187) (70,324) (131,844) (20,206) Deferred 19,776 64,887 22,508 3,450 ​ (24,411) (5,437) (109,336) (16,756) ​
Schedule of reconciliation of tax computed by applying the statutory income tax rate	The reconciliation of tax computed by applying the statutory income tax rate of 25% for the years ended December 31, 2018, 2019 and 2020 applicable to the PRC operations to income tax expenses were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2018 2019 2020 ​ RMB RMB RMB US$ Loss before income taxes (162,325) (175,809) (2,570,923) (394,010) Income tax benefits computed at applicable tax rates (25%) 40,581 43,952 642,731 98,503 Non-deductible expenses (2,834) (23,082) (4,117) (631) Research and development expenses 25,906 19,688 32,777 5,023 Preferential rate 11,701 20,213 26,554 4,070 Current and deferred tax rate differences 37,934 (8,699) (36,391) (5,577) International rate differences (63,525) (77,066) (711,962) (109,113) Tax exempted income — 754 1,087 167 PRC withholding tax ​ — ​ — ​ (10,263) ​ (1,573) Unrecognized tax benefits (expenses) 1,472 1,728 (58,449) (8,958) Change in valuation allowance (79,694) 25,423 6,465 991 Prior year provision to return true up 4,048 (8,348) 2,232 342 Income tax expenses (24,411) (5,437) (109,336) (16,756)
Schedule of significant components of deferred taxes	​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2019 2020 ​ RMB RMB US$ Deferred tax assets Non-current Allowance for doubtful debt 48,568 39,886 6,113 Impairment of long-lived assets ​ — ​ 13,467 ​ 2,064 Impairment of long-term investment ​ — ​ 2,150 ​ 330 Accrued expense 21,139 24,986 3,829 Tax losses 146,996 171,211 26,239 Property and equipment 20,567 22,631 3,468 Intangible assets 3,691 5,765 884 Finance lease 395,555 390,925 59,912 Deferred government grant 1,189 1,357 208 Operating lease 269,468 292,210 44,783 Loss picked up on equity method investments ​ 56,706 ​ 57,201 ​ 8,766 Valuation allowance (158,638) (170,104) (26,070) ​ ​ ​ ​ ​ ​ ​ Total deferred tax assets, net of valuation allowance 805,241 851,685 130,526 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities Non-current Intangible assets 104,217 186,258 28,545 Property and equipment 81,424 143,873 22,050 Capitalized interest expense 15,146 19,339 2,963 Finance lease ​ 326,407 ​ 313,102 ​ 47,985 Operating lease ​ 269,468 ​ 292,210 ​ 44,783 Investment in subsidiaries ​ — ​ 10,263 ​ 1,573 Gain picked up from equity method investments 1,785 252 39 ​ ​ ​ ​ ​ ​ ​ Total non-current deferred tax liabilities ​ 798,447 ​ 965,297 ​ 147,938 ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets (liabilities) ​ 6,794 ​ (113,612) ​ (17,412) Analysis as: ​ ​ ​ ​ ​ ​ Deferred tax assets ​ 209,366 ​ 185,481 ​ 28,426 Deferred tax liabilities ​ 202,572 ​ 299,093 ​ 45,838 ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets (liabilities) 6,794 (113,612) (17,412) ​
Schedule of roll-forward of unrecognized tax benefits	​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2019 2020 ​ RMB RMB US$ Balance at beginning of year 4,509 1,722 264 Reversal based on tax positions related to prior years (3,266) (629) (96) Additions based on tax positions related to the current year 479 61,491 9,423 Balance at end of year 1,722 62,584 9,591 ​

RELATED PARTY TRANSACTIONS (Tab

RELATED PARTY TRANSACTIONS (Tables)	12 Months Ended
	Dec. 31, 2020
RELATED PARTY TRANSACTIONS
Schedule of significant related party transactions	Other than disclosed elsewhere, the Company had the following significant related party transactions for the years ended December 31, 2018, 2019 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ 2018 2019 2020 ​ RMB RMB RMB US$ Services provided to: -Xiaomi Group 374,085 ​ 437,694 527,679 80,870 -Qidi Tech ​ — ​ 7,427 ​ 3,478 ​ 533 -Jingliang Inter Cloud ​ — ​ — ​ 880 ​ 135 -BJ Cheetah ​ 2,079 ​ 169 ​ 98 ​ 15 -BJ Kingsoft 6,281 ​ 3,475 43 7 -Taiji ​ 13,681 ​ 7,899 ​ — ​ — -WiFire BJ 16,490 ​ 1,934 — — -Unisvnet 1,011 ​ — — — -Others 4,493 ​ 1,494 305 47 ​ ​ ​ ​ ​ ​ ​ ​ ​ Services provided by: -CYSD ​ 18,667 ​ 38,918 ​ 38,918 ​ 5,964 -BJ Kingsoft ​ 13,204 ​ 3,492 ​ 16,867 ​ 2,585 -APL — — 8,124 1,245 -Jingliang Inter Cloud 3,477 8,829 4,956 760 -Beijing Huaqing ​ — ​ — ​ 4,389 ​ 673 -Taiji 7,095 19,942 — — -DCSS 5,238 — — — -BZRH 4,239 — — — -WiFire BJ ​ 4,066 ​ — ​ — ​ — -Others 6,396 5,866 796 122 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loan to: -Shanghai Puping ​ — ​ — ​ 62,531 ​ 9,583 -Taiji ​ — ​ 1,500 ​ — ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest income from loan to: -BJ Fastweb 700 700 — — ​ ​ ​ ​ ​ ​ ​ ​ ​ Lease deposit paid to: ​ ​ ​ -Ziguang Finance Leasing ​ 2,042 ​ 6,154 ​ 135 ​ 21 -Tuspark Harmonious 11,472 — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ Lease payment paid to: -Tuspark Harmonious ​ — ​ 68,832 ​ 43,703 ​ 6,698 -Ziguang Finance Leasing 4,897 17,156 30,776 4,717 -Beijing Qidi Yefeng ​ — ​ — ​ 4,516 ​ 692 ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash consideration for shares repurchase ​ ​ ​ ​ ​ ​ ​ ​ -King Venture ​ — ​ — ​ 130,472 ​ 19,996
Schedule of related party balances	​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2019 2020 ​ RMB RMB US$ Amounts due from related parties: Current: -Shanghai Puping ​ — ​ 62,531 ​ 9,583 -SH Shibei ​ 9,800 ​ 9,800 ​ 1,502 -Ziguang Finance Leasing ​ — ​ 2,042 ​ 313 -Marble SH (2) ​ 100,106 ​ — ​ — -Shihua Investment Group (3) ​ 82,542 ​ — ​ — -Xiaomi Group 39,778 — — -Marble Holdings (2) ​ 29,736 ​ — ​ — -Shihua Investment Management (3) ​ 27,905 ​ — ​ — -Taiji 9,499 — — -Qidi Tech ​ 1,249 ​ — ​ — -Others 1,050 1,146 176 ​ 301,665 75,519 11,574 Non-current: -Tuspark Harmonious 11,863 11,863 1,818 -Ziguang Finance Leasing 8,195 6,289 964 -Beijing Qidi Yefeng ​ — ​ 1,124 ​ 172 -Others ​ 596 ​ 1,286 ​ 197 ​ 20,654 20,562 3,151 Amounts due to related parties: Current: -Ziguang Finance Leasing 27,160 31,681 4,855 -Tuspark Harmonious 24,917 13,557 2,078 -Beijing Qidi Yefeng ​ — ​ 4,410 ​ 676 -Shihua Investment Group (3) ​ 84,021 ​ — ​ — -Shihua Investment Management (3) ​ 22,484 ​ — ​ — -WiFire BJ (1) ​ 6,330 ​ — ​ — -BJ Kingsoft 1,073 — — -APL ​ — ​ 783 ​ 120 -Others 950 576 88 ​ 166,935 51,007 7,817 Non-current: -Tuspark Harmonious 698,511 715,992 109,731 -Ziguang Finance Leasing 47,388 22,247 3,409 -Beijing Qidi Yefeng ​ — ​ 9,507 ​ 1,457 ​ 745,899 747,746 114,597 ​ (1) In 2019, RMB20,367 of amounts due from/to WiFire Entities were offset according to the multi-party debt offset agreement signed in 2019. The remaining RMB52,142 of amounts due from WiFire Entities was fully impaired considering low collectability. (2) Amounts due from Marble SH and Marble Holdings represented the unpaid cash consideration to the Company for acquiring the 100% equity interest in certain of Shihua Holdings 2’s subsidiaries in 2019 (Note 4). (3) Amounts due from/to Shihua Investment Management and Shihua Invesetment Group were generated from the assets acquisition of Shihua Holdings 2 (Note 4).

LOSS PER SHARE (Tables)

LOSS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2020
LOSS PER SHARE
Schedule of basic and diluted loss per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ Net loss (186,736) (181,246) (2,680,259) (410,766) Net profit attributable to noncontrolling interest (18,329) (1,046) (29,088) (4,458) Net loss attributable to the Company (205,065) (182,292) (2,709,347) (415,224) Plus undeclared cumulative dividend on perpetual convertible preferred shares — — (22,806) (3,495) Deemed distribution to perpetual convertible preferred shareholders ​ — ​ — ​ (470,643) ​ (72,129) Adjusted net loss attributable to ordinary shareholders (205,065) (182,292) (3,202,796) (490,848) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: Weighted average number of shares outstanding—basic ​ 674,732,130 ​ 668,833,756 ​ 716,888,919 ​ 716,888,919 Weighted average number of shares outstanding—diluted ​ 674,732,130 ​ 668,833,756 ​ 716,888,919 ​ 716,888,919 Loss per share—Basic: Net loss (0.30) (0.27) (4.47) (0.69) ​ (0.30) (0.27) (4.47) (0.69) Loss per share—Diluted: ​ Net loss (0.30) (0.27) (4.47) (0.69) ​ (0.30) (0.27) (4.47) (0.69) ​

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
FAIR VALUE MEASUREMENTS
Summary of assets and liabilities measured at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurement using: ​ ​ Quoted prices in ​ Significant other ​ ​ ​ ​ ​ ​ active markets for ​ observable ​ Unobservable ​ ​ ​ ​ identical assets ​ inputs ​ inputs ​ Fair value at ​ ​ (Level 1) ​ (Level 2) ​ (Level 3) ​ December 31, 2019 ​ RMB RMB RMB RMB Cash equivalents: - Time deposits 117,825 — — 117,825 Short-term investments: ​ ​ - Time deposits 363,856 — — 363,856 Long-term investments - Available-for-sale debt securities — — 1,713 1,713 Assets 481,681 — 1,713 483,394 ​ ​ ​ ​ ​ ​ ​ ​ ​ Short-term borrowings: ​ ​ ​ ​ ​ ​ ​ ​ - Current portion of bonds payable ​ 912,416 ​ — ​ — ​ 912,416 Long-term borrowings: - Bonds payable 2,089,114 — — 2,089,114 Other liabilities: - Liability classified RSU — — 2,109 2,109 Liabilities 3,001,530 — 2,109 3,003,639 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value measurement using: ​ ​ ​ ​ ​ ​ Quoted prices in ​ Significant other ​ ​ ​ ​ ​ ​ ​ ​ active markets for ​ observable ​ Unobservable ​ ​ ​ ​ ​ ​ identical assets ​ inputs ​ inputs ​ Fair value at ​ ​ (Level 1) ​ (Level 2) ​ (Level 3) ​ December 31, 2020 ​ RMB RMB RMB RMB US$ Cash equivalents: - Time deposits 645,879 — — 645,879 98,985 Short-term investments: - Time deposits 285,872 — — 285,872 43,812 Long-term investments: ​ ​ ​ ​ ​ - Available-for-sale debt securities — — 1,713 1,713 263 Assets 931,751 — 1,713 933,464 143,060 Short-term borrowings: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ - Current portion of bonds payable ​ 1,998,088 ​ — ​ — ​ 1,998,088 ​ 306,220 Convertible promissory notes ​ — ​ — ​ 3,014,057 ​ 3,014,057 ​ 461,924 Other liabilities: ​ - Liability classified RSU — — — — — Liabilities 1,998,088 — 3,014,057 5,012,145 768,144
Summary of reconciliation of all liabilities measured at fair value on a recurring basis using significant unobservable inputs (level 3)	​ ​ ​ ​ ​ Liability classified ​ ​ RSU ​ ​ RMB Fair value at January 1, 2019 4,970 Reclassification to equity (2,861) Reversal ​ — Transfers in and/or out of Level 3 — Fair value at December 31, 2019 2,109 Reclassification to equity (2,109) Reversal — Transfers in and/or out of Level 3 — Fair value at December 31, 2020 — Fair value at December 31, 2020 (US$) — ​ ​ ​ ​ ​ ​ ​ Convertible promissory notes ​ ​ RMB ​ US$ Convertible promissory notes fair value (Note 18) 1,409,385 215,998 Foreign exchange loss (219,001) (33,564) Changes in the fair value 2,544,220 389,919 Reclassification to equity (720,547) (110,429) Transfers in and/or out of Level 3 — — Fair value at December 31, 2020 3,014,057 461,924

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2020
Schedule of commitments to purchase certain computer and network equipment and construction-in-progress
Purchase Commitments	As of December 31, 2020, the Company has the following commitments to purchase certain computer and network equipment and construction-in-progress: ​ ​ ​ ​ ​ ​ ​ RMB US$ For the year ending December 31, ​ ​ ​ ​ 2021 ​ 1,678,273 ​ 257,207 2022 and thereafter — — ​ 1,678,273 257,207
Schedule of outstanding purchase commitments in relation to bandwidth and cabinet capacity
Purchase Commitments	As of December 31, 2020, the Company has outstanding purchase commitments in relation to bandwidth and cabinet capacity consisting of the following: ​ ​ ​ ​ ​ ​ ​ RMB US$ For the year ending December 31, ​ ​ ​ ​ 2021 706,715 108,309 2022 149,331 22,886 2023 6,458 990 2024 2,189 335 2025 and thereafter 6,512 998 ​ 871,205 133,518

PARENT COMPANY ONLY CONDENSED_2

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2020
Related Party Transaction [Line Items]
Condensed Balance Sheets	Condensed balance sheets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ Notes ​ 2019 ​ 2020 ​ ​ RMB RMB US$ ASSETS Current assets Cash and cash equivalents ​ ​ 243,989 62,116 9,520 Short-term investments ​ ​ 138,848 — — Prepaid expenses and other current assets ​ ​ 105,597 97,391 14,925 Amounts due from subsidiaries (b) 6,128,595 9,320,580 1,428,441 Total current assets ​ ​ 6,617,029 9,480,087 1,452,886 ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current assets ​ ​ Investments in subsidiaries ​ ​ 1,446,563 2,169,222 332,448 Total non-current assets ​ ​ 1,446,563 2,169,222 332,448 Total assets ​ ​ 8,063,592 11,649,309 1,785,334 LIABILITIES AND SHAREHOLDERS’ EQUITY ​ ​ ​ Current liabilities: ​ ​ ​ Accrued expenses and other payables ​ ​ 57,612 49,648 7,609 Account payables ​ ​ 56 52 8 Interest payable ​ ​ 58,525 37,353 5,725 Current portion of bonds payable ​ ​ ​ 911,147 ​ 1,943,619 ​ 297,873 Amount due to related parties ​ — 783 120 Amounts due to subsidiaries (b) 22,471 38,863 5,955 Total current liabilities ​ ​ 1,049,811 2,070,318 317,290 ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current liabilities ​ ​ Bonds payable (c) 2,060,708 — — Convertible promissory notes ​ ​ ​ — ​ 3,014,057 ​ 461,924 Total non-current liabilities ​ ​ 2,060,708 3,014,057 461,924 Total liabilities ​ ​ 3,110,519 5,084,375 779,214 Shareholders’ equity: ​ ​ ​ ​ Class A Ordinary shares (par value of US$0.00001 per share; 1,200,000,000 and 1,199,790,000 shares authorized; 505,253,850 and 672,024,600 shares issued outstanding ​ ​ 34 44 7 Class B Ordinary shares (par value of US$0.00001 per share; 300,000,000 and 300,000,000 shares authorized; 174,649,638 and 145,875,113 shares issued outstanding ​ ​ 12 12 2 Class C Ordinary shares (par value of US$0.00001 per share; 60,000 and 60,000 shares authorized; 60,000 and 60,000 shares issued outstanding ​ ​ ​ — ​ — ​ — Series A perpetual convertible preferred shares (par value of US$0.00001 per share; nil and 150,000 shares issued and outstanding ​ ​ ​ — ​ 1,047,468 ​ 160,531 Additional paid-in capital ​ ​ 9,202,567 13,083,119 2,005,076 Accumulated other comprehensive loss (income) ​ ​ 77,904 (55,535) (8,511) Accumulated deficit ​ ​ (3,977,921) (7,160,651) (1,097,418) Treasury stock ​ ​ (349,523) (349,523) (53,567) Total shareholders’ equity ​ ​ 4,953,073 6,564,934 1,006,120 Total liabilities and shareholders’ equity ​ ​ 8,063,592 11,649,309 1,785,334
Condensed Statements of Operations	Condensed statements of operations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Operating Expenses General and administrative expenses (65,949) (44,490) (94,175) (14,433) Changes in the fair value of contingent purchase consideration payables 13,905 — — — Operating loss (52,044) (44,490) (94,175) (14,433) Other loss (262,186) (274,572) (168,656) (25,846) Changes in the fair value of convertible promissory notes ​ — ​ — ​ (2,544,220) ​ (389,919) Share of profits from subsidiaries and Consolidated VIEs 109,165 136,770 97,704 14,974 Net loss attributable to 21Vianet Group, Inc. (205,065) (182,292) (2,709,347) (415,224) Income tax expense — — — — Net loss (205,065) (182,292) (2,709,347) (415,224)
Condensed Statements of Comprehensive Loss	Condensed statements of comprehensive loss ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Net loss (205,065) (182,292) (2,709,347) (415,224) Other comprehensive income (loss), net of tax of nil: ​ ​ Foreign currency translation adjustments, net of tax of nil 88,652 (8,075) (133,439) (20,450) Other comprehensive income (loss), net of tax of nil: 88,652 (8,075) (133,439) (20,450) Comprehensive loss (116,413) (190,367) (2,842,786) (435,674) Comprehensive loss attributable to 21Vianet Group, Inc. (116,413) (190,367) (2,842,786) (435,674)
Condensed Statements of Cash Flows	Condensed statements of cash flows ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the years ended December 31, ​ ​ 2018 ​ 2019 ​ 2020 ​ RMB RMB RMB US$ Net cash used in operating activities (166,068) (142,989) (743,944) (114,014) Net cash used in investing activities (203,651) (1,011,257) (3,036,370) (465,344) Net cash generated from financing activities 43,145 807,765 3,598,441 551,485 Net decrease in cash and cash equivalents and restricted cash (326,574) (346,481) (181,873) (27,873) Cash and cash equivalents and restricted cash at beginning of the year 917,044 590,470 243,989 37,393 Cash and cash equivalents and restricted cash at end of the year 590,470 243,989 62,116 9,520
Parent Company
Related Party Transaction [Line Items]
Schedule of significant related party transactions	The Company had the following related party balances as of December 31, 2019 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2019 ​ 2020 ​ RMB RMB US$ Amounts due from subsidiaries - 21Vianet HK 5,855,452 7,043,586 1,079,477 - WiFire Open Network Group Ltd. ​ 147,326 ​ 2,157,285 ​ 330,618 - HongKong Fastweb Holdings Co., Ltd. 67,088 62,780 9,621 - 21V Mobile 58,018 56,265 8,623 - WiFire Group 698 652 100 - Others 13 12 2 ​ 6,128,595 9,320,580 1,428,441 Amounts due to subsidiaries - 21Vianet Beijing 19,449 35,783 5,484 - Others 3,022 3,080 471 ​ 22,471 38,863 5,955

ORGANIZATION - Significant subs

ORGANIZATION - Significant subsidiaries of the Company and consolidated variable interest entities (Details)	12 Months Ended
	Dec. 31, 2020
21ViaNet Group Limited ("21Vianet HK") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
21Vianet Data Center Co., Ltd. ("21Vianet China") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
21Vianet (Foshan) Technology Co., Ltd. ("FS Technology") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
21Vianet Anhui Suzhou Technology Co., Ltd.("SZ Technology") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
21Vianet Hangzhou Information Technology Co.,Ltd. ("HZ Technology") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
iJoy Holding Limited ("iJoy BVI") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
21Vianet Mobile Limited ("21V Mobile") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
WiFire Group Inc. ("WiFire Group") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Joytone Infotech Co., Ltd. ("SZ Zhuoaiyi") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
21Vianet Ventures Limited (Ventures) | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Abitcool (China) Broadband Inc. ("aBitCool DG") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Diyixian.com Limited ("Diyixian.com") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
21Vianet Zhuhai Financial Leasing Limited | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
21Vianet DRP Investment Holdings Limited [Member] | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Shihua DC Investment Holdings Limited. | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	51.00%
21Vianet (Xi'an) Technology Co., Ltd. ("Xi'an Tech") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	51.00%
Foshan Zhuoyi Intelligence Date Co., Ltd. ("FS Zhuoyi") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	51.00%
Beijing Hongyuan Network Technology Co., Ltd [Member] | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	51.00%
Dermot Holding Limited [Member] | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Shihua DC Investment Holdings 2 Limited ("Shihua Holdings 2") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Shanghai Waigaoqiao Free Trade Zone Hongming Logistics Co., Ltd. ("Hongming Logistics") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Shanghai Edge Connect Technology Co., Ltd. ("SH Edge Connect") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Beijing Jianghe Cloud Technology Co.,Ltd. ("BJ JHC") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Beijing Shuntou Green Energy Data Technology Co.,Ltd. ("BJ ST") | Subsidiaries
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%
Shenzhen Diyixian Telecommunication Co., Ltd [Member] | Variable Interest Entity, Primary Beneficiary
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of direct ownership by the Company	100.00%

ORGANIZATION - Significant su_2

ORGANIZATION - Significant subsidiaries of the Company and consolidated variable interest entities (Parenthetical) (Details)	Nov. 17, 2020	Sep. 11, 2020	Jul. 21, 2020	Jun. 30, 2020	Jun. 24, 2020	Aug. 10, 2014
Dermot Entities
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of equity interests acquired						100.00%
SH Shuzhong
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of equity interests acquired				100.00%
Shulifang
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of equity interests acquired			100.00%		100.00%
LF Huahai
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of equity interests acquired		100.00%
BJ JHC
Significant subsidiaries of the Company, VIEs and subsidiaries of VIEs
Percentage of equity interests acquired	100.00%

ORGANIZATION - Additional Infor

ORGANIZATION - Additional Information (Details) $ in Thousands	Aug. 20, 2019	Dec. 19, 2016CNY (¥)	Jan. 31, 2011CNY (¥)	Aug. 31, 2019	Mar. 31, 2017item	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2018	Mar. 14, 2017
Organization
Assets pledged as collateral						¥ 134,415,000	$ 20,600
Consolidated VIE's assets pledged as collateral						0
Consolidated VIE's liabilities pledged as collateral						¥ 0
Internet Data Center Services
Organization
Equity interest percentage by parent					51.00%				51.00%
Number of internet data centers | item					4
Warburg Pincus
Organization
Equity interest percentage by parent					49.00%				49.00%
Equity interest percentage					49.00%			49.00%
Shihua DC Investment Holdings 2 Limited ("Shihua Holdings 2") | Warburg Pincus
Organization
Percentage of equity interest transferred	100.00%			100.00%
Option Agreement
Organization
Exclusive option price		¥ 1
Agreement agreement between 21Vianet China and the 21Vianet Technology, term		10 years				10 years
Agreement agreement between 21Vianet China and the 21Vianet Technology, expiration date		Dec. 18, 2026				Dec. 18, 2016
Technical Consulting and Service Agreement
Organization
Agreement agreement between 21Vianet China and the 21Vianet Technology, term		10 years				10 years
Agreement agreement between 21Vianet China and the 21Vianet Technology, expiration date		Dec. 18, 2026				Dec. 18, 2016
Service fee per hour						¥ 1,000
Loan Agreement | Shareholders | Loan one
Organization
Loan facility provided to related parties			¥ 7,000,000
Loan Agreement | Shareholders | Loan Two
Organization
Loan facility provided to related parties			¥ 3,000,000

ORGANIZATION - Financial inform

ORGANIZATION - Financial information of the consolidated VIEs (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Current assets:
Cash and cash equivalents	¥ 2,710,349		¥ 1,808,483	¥ 2,358,556	$ 415,379
Restricted cash	270,450		478,873	265,214	41,448
Prepaid expenses and other current assets	1,866,184		1,618,149		286,005
Amounts due from related parties	75,519		301,665		11,574
Total current assets	6,055,607		5,228,184		928,062
Non-current assets:
Property and equipment, net	8,106,425		5,443,565		1,242,364
Intangible assets, net	658,195		410,595	355,313	100,873
Land use rights, net	255,373		233,154		39,138
Operating lease right-of-use assets, net	1,325,526		1,221,616		203,146
Goodwill	994,993		989,530	989,530	152,489	$ 151,652
Restricted cash	135,638		69,821	37,251	20,787
Deferred tax assets, net	185,481		209,366		28,426
Amounts due from related parties	20,562		20,654		3,151
Other non-current assets	1,500,438		277,568		229,952
Long-term investments, net	135,517		169,653		20,769
Total non-current assets	13,318,148		9,045,522		2,041,095
Total assets	19,373,755		14,273,706		2,969,157
Current liabilities:
Short-term bank borrowings	34,000		234,500		5,211
Accounts payable and notes payable	289,387		303,128		44,350
Accrued expenses and other payables	1,631,563		978,935		250,048
Advance from customers	1,041,594		1,068,692		159,631
Deferred revenue	63,245		57,625		9,693
Income tax payable	29,028		48,032		4,449
Amounts due to related parties	51,007		166,935		7,817
Current portion of finance lease liabilities	403,843		227,115		61,892
Current portion of long-term borrowings	68,500		32,500		10,498
Current portion of deferred government grant	2,074		2,595		318
Current portion of operating lease liabilities	452,272		437,817		69,314
Total current liabilities	6,121,960		4,469,021		938,232
Non-current liabilities:
Amounts due to related parties-non current	747,746		745,899		114,597
Non-current portion of finance lease liabilities	688,128		896,927		105,460
Unrecognized tax benefits	68,696		2,443		10,528
Deferred tax liabilities	299,093		202,572		45,838
Non-current portion of deferred government grant	4,100		5,906		628
Non-current portion of operating lease liabilities	645,499		579,102		98,927
Total non-current liabilities	6,354,315		4,573,057		973,840
Total liabilities	12,476,275		9,042,078		1,912,072
Net profit	(2,680,259)	$ (410,766)	(181,246)	(186,736)
Net cash generated from operating activities	714,243	109,464	802,922	704,966
Net cash generated from (used in) investing activities	(3,889,174)	(596,043)	(1,611,983)	(304,846)
Net cash (used in) generated from financing activities	4,163,255	638,046	461,557	(19,901)
Variable Interest Entity, Primary Beneficiary
Current assets:
Cash and cash equivalents	737,556		591,503		113,035
Restricted cash	260,450		260,961		39,916
Accounts receivable (net of allowance for doubtful debt of RMB66,416 and RMB67,632 (US$10,365) as of December 31, 2019 and 2020, respectively)	664,610		513,440		101,856
Prepaid expenses and other current assets	1,622,662		1,371,564		248,684
Amounts due from related parties	12,968		57,982		1,987
Total current assets	3,298,246		2,795,450		505,478
Non-current assets:
Property and equipment, net	5,170,878		3,580,341		792,472
Intangible assets, net	342,288		151,722		52,458
Land use rights, net	46,719		58,588		7,160
Operating lease right-of-use assets, net	1,134,073		1,144,846		173,804
Goodwill	308,110		302,647		47,220
Restricted cash	27,719		66,119		4,248
Deferred tax assets, net	168,181		180,959		25,775
Amounts due from related parties	20,562		20,654		3,151
Other non-current assets	435,144		262,685		66,689
Long-term investments, net	172,593		189,571		26,451
Total non-current assets	7,826,267		5,958,132		1,199,428
Total assets	11,124,513		8,753,582		1,704,906
Current liabilities:
Short-term bank borrowings	34,000		232,323		5,211
Accounts payable and notes payable	182,669		211,710		27,995
Accrued expenses and other payables	981,961		622,160		150,492
Advance from customers	1,041,594		1,068,692		159,631
Deferred revenue	58,066		52,088		8,899
Income tax payable	12,743		8,175		1,953
Amounts due to inter-companies	4,248,422		2,786,838		651,099
Amounts due to related parties	50,193		56,977		7,692
Current portion of finance lease liabilities	362,760		220,363		55,595
Current portion of long-term borrowings	165,328		32,500		25,338
Current portion of deferred government grant	2,074		2,595		318
Current portion of operating lease liabilities	427,114		410,422		65,458
Total current liabilities	7,566,924		5,704,843		1,159,681
Non-current liabilities:
Amounts due to inter-companies	1,020,972		1,020,972		156,471
Amounts due to related parties-non current	747,746		745,899		114,597
Long-term borrowings	570,135		79,500		87,377
Non-current portion of finance lease liabilities	299,399		549,669		45,885
Unrecognized tax benefits	68,317		1,991		10,470
Deferred tax liabilities	155,281		82,725		23,798
Non-current portion of deferred government grant	4,100		5,906		628
Non-current portion of operating lease liabilities	497,268		529,546		76,210
Total non-current liabilities	3,363,218		3,016,208		515,436
Total liabilities	10,930,142		8,721,051		$ 1,675,117
Revenues	3,885,141	595,424	2,858,176	2,532,854
Net profit	73,748	11,302	111,592	52,986
Net cash generated from operating activities	748,418	114,700	495,308	693,620
Net cash generated from (used in) investing activities	(1,943,358)	(297,833)	(1,247,764)	132,522
Net cash (used in) generated from financing activities	1,302,082	199,553	885,286	(423,467)
Net increase in cash and cash equivalents and restricted cash	¥ 107,142	$ 16,420	¥ 132,830	¥ 402,705

ORGANIZATION - Financial info_2

ORGANIZATION - Financial information of the consolidated VIEs (Parenthetical) (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity
Accounts receivable, allowance for doubtful accounts	¥ 67,632	$ 10,365	¥ 66,416

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Estimated useful lives of property and equipment (Details)	12 Months Ended
	Dec. 31, 2020
Property | Minimum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	25 years
Property | Maximum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	46 years
Optical Fibers | Minimum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	10 years
Optical Fibers | Maximum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	20 years
Computer and network equipment | Minimum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	1 year
Computer and network equipment | Maximum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	10 years
Office equipment | Minimum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	2 years
Office equipment | Maximum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	8 years
Motor vehicles | Minimum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	2 years
Motor vehicles | Maximum
PROPERTY AND EQUIPMENT, NET
Property and equipment, estimated useful life (in years)	8 years

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Weighted average useful lives of intangible assets (Details)	12 Months Ended
	Dec. 31, 2020
Purchased software
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	5 years 1 month 6 days
Radio Spectrum License
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	15 years
Operating permits
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	29 years 3 months 18 days
Contract Backlog
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	4 years 10 months 24 days
Customer Relationships
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	8 years 9 months 18 days
Licenses
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	15 years
Supplier Relationships
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	10 years
Trade Names
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	20 years
Platform Software
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	5 years
Non-compete agreement
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	5 years
Internal-use Software
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	3 years 9 months 18 days
Customer contract
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	6 years 6 months

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impairment charges associated with its long-lived assets and acquired intangibles (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Long-lived assets impairment	¥ 81,619	$ 12,509
Discount rate	13.00%	13.00%
Impairment of equipment	¥ 35,793	$ 5,486
Impairment of intangible assets	38,654	5,924
Impairment of other non-current assets	7,172	1,099
Other Asset Impairment Charges	¥ 7,172	$ 1,099

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Interest expenses (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Interest expense and amortization cost of bonds payable	¥ 223,785	$ 34,297	¥ 223,832	¥ 150,098
Interest expense on convertible promissory notes	18,880	2,893
Interest expense on bank and other borrowings	39,424	6,042	14,212	19,395
Interest expense on finance leases	130,196	19,953	120,185	79,935
Total interest costs	412,285	63,185	358,229	249,428
Less: Total interest costs capitalized	(31,676)	(4,854)	(12,274)	(13,362)
Interest expenses, net	¥ 380,609	$ 58,331	¥ 345,955	¥ 236,066

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details) ¥ in Thousands, $ in Thousands	Dec. 02, 2019USD ($)	Jan. 01, 2019	Dec. 31, 2020CNY (¥)segmentshares	Dec. 31, 2020USD ($)segmentshares	Dec. 31, 2019CNY (¥)segmentshares	Dec. 31, 2018CNY (¥)segmentshares	Dec. 31, 2020USD ($)	Jan. 01, 2020CNY (¥)
Significant accounting policies
Accumulated deficit			¥ (7,235,113)		¥ (4,038,390)		$ (1,108,830)
Recorded credit loss			2,393	$ 367	1,557	¥ (598)
Internal use software development costs, Amount capitalized			¥ 8,684		¥ 13,189	¥ 6,093	1,331
Lease, Practical Expedients, Package		true
Percentage of interest in limited partnerships applies the equity method of accounting			3.00%	3.00%
Number of reporting units | segment			1	1	1	1
Deferred revenue			¥ 63,245		¥ 57,625		$ 9,693
Revenue recognized			46,730	$ 7,162
Advertising expense			¥ 7,779	$ 1,192	¥ 6,095	¥ 7,968
Share repurchase plan, shares repurchased (in shares) | shares			0	0	242,830	0
Share Repurchase Plan, share value					¥ 11,840
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update (ASU) 2016-13
Significant accounting policies
Accumulated deficit								¥ 2,740
American Depository Shares
Significant accounting policies
Share Repurchase Plan, period	13 months
Share repurchase plan, shares repurchased (in shares) | shares			0	0	242,830	0
Share Repurchase Plan, share value			¥ 0		¥ 11,840	¥ 0
Maximum
Significant accounting policies
Official exchange rate of foreign currency remeasured (RMB per one U.S. dollar)			6.5250				6.5250
Maximum | American Depository Shares
Significant accounting policies
Share Repurchase Plan, value | $	$ 20,000

CONCENTRATION OF RISKS (Details

CONCENTRATION OF RISKS (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)itemcustomer	Dec. 31, 2019CNY (¥)customeritem	Dec. 31, 2018customeritem	Dec. 31, 2020USD ($)item	Dec. 31, 2019USD ($)item
CONCENTRATION OF RISKS
Depreciation (appreciation) of RMB against US$	(6.50%)	1.60%	5.00%
Customer Concentration Risk
CONCENTRATION OF RISKS
Number of customers who contributed more than 3% of Company's revenue | customer	0	0	0
Cabinet and Bandwidth Supply
CONCENTRATION OF RISKS
Number of suppliers | item	5	5	5	5	5
Cabinet and Bandwidth Supply | Supplier Concentration Risk
CONCENTRATION OF RISKS
Concentration of risk, percentage	39.00%	21.00%	19.00%
Bandwidth and Cabinet Resources | Customer Concentration Risk
CONCENTRATION OF RISKS
Concentration of risk, percentage	3.00%	4.00%	4.00%
Bandwidth and Cabinet Resources | Customer Concentration Risk | Largest single customer | Maximum
CONCENTRATION OF RISKS
Concentration of risk, percentage	10.00%	8.00%	9.00%
PRC | Credit Concentration Risk
CONCENTRATION OF RISKS
Cash and cash equivalents, restricted cash and short-term investments, held at major institutions	¥ 1,419,855	¥ 1,171,075		$ 217,602
Outside the PRC | Credit Concentration Risk
CONCENTRATION OF RISKS
Cash and cash equivalents, restricted cash and short-term investments, held at major institutions	¥ 1,982,454			$ 303,824	$ 222,638

ACQUISITION AND DISPOSAL OF S_3

ACQUISITION AND DISPOSAL OF SUBSIDIARIES (Details) ¥ in Thousands, $ in Thousands	Nov. 17, 2020CNY (¥)	Nov. 17, 2020USD ($)	Sep. 11, 2020CNY (¥)	Sep. 11, 2020USD ($)	Jun. 24, 2020CNY (¥)	Jun. 24, 2020USD ($)	Dec. 24, 2019CNY (¥)	Aug. 20, 2019CNY (¥)	Jun. 30, 2020CNY (¥)	Jun. 30, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Nov. 17, 2020USD ($)	Sep. 11, 2020USD ($)	Jun. 30, 2020USD ($)	Jun. 24, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018CNY (¥)
Net assets acquired:
Goodwill											¥ 989,530	¥ 994,993	$ 152,489					$ 151,652	¥ 989,530
BJ JHC
Net assets acquired:
Property and equipment, net	¥ 279,556													$ 42,843
Operating lease right-of-use assets, net	112,398													17,226
Deferred tax assets	3,150													483
Other non-current assets	4,428													678
Cash and cash equivalents	30,319													4,647
Other current assets	8,833													1,354
Other current liabilities	(90,805)													(13,916)
Operating lease liabilities	(120,120)													(18,409)
Finance lease liabilities	(84,082)													(12,886)
Deferred tax liabilities	(55,288)													(8,473)
Total purchase consideration in cash	232,015	$ 35,558
BJ JHC | Operating permits
Net assets acquired:
Intangible assets	110,418													16,922
BJ JHC | Customer contract
Net assets acquired:
Intangible assets	¥ 33,208													$ 5,089
SH Shuzhong
Net assets acquired:
Property and equipment, net									¥ 348,475							$ 53,406
Operating lease right-of-use assets, net									81,034							12,419
Deferred tax assets									14,848							2,275
Other current assets									44,774							6,862
Other current liabilities									(406,932)							(62,365)
Operating lease liabilities									(45,034)							(6,902)
Deferred tax liabilities									(41,169)							(6,309)
Total assets acquired									524,339							80,358
Total liabilities assumed									(493,135)							(75,576)
Net assets acquired									31,204							4,782
Total purchase consideration in cash									36,667	$ 5,619
Goodwill									5,463							837
SH Shuzhong | Customer contract
Net assets acquired:
Intangible assets									33,500							5,134
Other non-current assets									1,685							258
SH Shuzhong | Purchased software
Net assets acquired:
Intangible assets									¥ 23							$ 4
Shulifang
Net assets acquired:
Operating lease right-of-use assets, net					¥ 15,206												$ 2,330
Other non-current assets					15,409												2,362
Cash and cash equivalents					53												8
Other current assets					601												91
Deferred tax liabilities					(11,284)												(1,729)
Lease liabilities					(15,206)												(2,330)
Non-current payables					(16,913)												(2,592)
Total purchase consideration in cash					33,000	$ 5,057
Shulifang | Operating permits
Net assets acquired:
Intangible assets					¥ 45,134												$ 6,917
LF Huahai
Net assets acquired:
Operating lease right-of-use assets, net			¥ 183,174												$ 28,073
Other non-current assets			27,524												4,218
Cash and cash equivalents			173												27
Other current assets			4,088												627
Other current liabilities			(35,600)												(5,456)
Deferred tax liabilities			(29,838)												(4,573)
Lease liabilities			(183,873)												(28,180)
Total purchase consideration in cash			85,000	$ 13,027
LF Huahai | Operating permits
Net assets acquired:
Intangible assets			¥ 119,352												$ 18,291
Beijing Shuhai Data Technology Co., Ltd ("BJ Shuhai")
Net assets acquired:
Intangible assets											100,380
Operating lease right-of-use assets, net											129,937
Cash and cash equivalents											59
Other current assets											9,625
Other current liabilities											(16,714)
Deferred tax liabilities											(25,095)
Lease liabilities											(129,937)
Total purchase consideration in cash											¥ 68,255
Shihua DC Investment Holdings 2 Limited ("Shihua Holdings 2")
Net assets acquired:
Construction-in-progress								¥ 465
Cash and cash equivalents								67,563
Other current assets								1,333,329
Other current liabilities								(1,203,894)
Deferred tax liabilities								(33,096)
Fixed assets								150,880
Total purchase consideration in cash								¥ 315,247
Nantong Chenghong Cloud Computing Co., Ltd. ("NT Chenghong")
Net assets acquired:
Property and equipment, net							¥ 13
Construction-in-progress							158,471
Cash and cash equivalents							129
Other current assets							11,840
Other current liabilities							(88,830)
Deferred tax liabilities							(1,623)
Total purchase consideration in cash							¥ 80,000

ACQUISITION AND DISPOSAL OF S_4

ACQUISITION AND DISPOSAL OF SUBSIDIARIES - Additional Information (Details) ¥ in Thousands, $ in Thousands	Nov. 17, 2020CNY (¥)	Nov. 17, 2020USD ($)	Oct. 28, 2020CNY (¥)	Oct. 28, 2020USD ($)	Sep. 11, 2020CNY (¥)	Sep. 11, 2020USD ($)	Jun. 30, 2020CNY (¥)	Jun. 30, 2020USD ($)	Jun. 24, 2020CNY (¥)	Jun. 24, 2020USD ($)	Dec. 24, 2019CNY (¥)	Aug. 20, 2019	Jan. 02, 2019CNY (¥)	Aug. 31, 2019	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)	Dec. 31, 2020USD ($)	Nov. 17, 2020USD ($)	Jul. 21, 2020	Mar. 31, 2017
Business Acquisition [Line Items]
Cash consideration															¥ 1,302,601	$ 199,633	¥ 82,536	¥ 13,000
BJ JHC
Business Acquisition [Line Items]
Equity interests acquired (as a percent)	100.00%																			100.00%
Cash consideration	¥ 432,015	$ 66,209
Contingent consideration asset															200,000				$ 30,651
Contingent consideration liability	¥ 200,000																			$ 30,651
Prepayments amounting to acquire potential equity interest															844,309	129,396
SH Shuzhong
Business Acquisition [Line Items]
Equity interests acquired (as a percent)							100.00%	100.00%
Cash consideration							¥ 36,667	$ 5,619
Revenue of acquiree since the acquisition date included in the consolidated statement of operations															41,928	6,426
Net profit of acquiree since the acquisition date included in the consolidated statement of operations															¥ 5,579	$ 855
Shulifang
Business Acquisition [Line Items]
Equity interests acquired (as a percent)									100.00%												100.00%
Cash consideration									¥ 43,000	$ 6,590
Contingent consideration liability									¥ 10,000										$ 1,533
LF Huahai
Business Acquisition [Line Items]
Equity interests acquired (as a percent)					100.00%	100.00%
Cash consideration			¥ 25,500	$ 3,908	¥ 59,500	$ 9,119
SH Shilian
Business Acquisition [Line Items]
Equity interests acquired (as a percent)					69.93%	69.93%
21Vianet Saturn
Business Acquisition [Line Items]
Equity interests acquired (as a percent)			30.07%	30.07%
Beijing Shuhai Data Technology Co., Ltd ("BJ Shuhai")
Business Acquisition [Line Items]
Equity interests acquired (as a percent)													100.00%
Cash consideration													¥ 98,255
Contingent consideration liability																	¥ 30,000
Shihua DC Investment Holdings 2 Limited ("Shihua Holdings 2")
Business Acquisition [Line Items]
Equity interest (as a percentage)												49.00%										49.00%
Nantong Chenghong Cloud Computing Co., Ltd. ("NT Chenghong")
Business Acquisition [Line Items]
Equity interests acquired (as a percent)											100.00%
Cash consideration											¥ 80,000
Warburg Pincus | Shihua DC Investment Holdings 2 Limited ("Shihua Holdings 2")
Business Acquisition [Line Items]
Equity interest (as a percentage)																						51.00%
Percentage of equity interest transferred												100.00%		100.00%

ACCOUNTS AND NOTES RECEIVABLE_3

ACCOUNTS AND NOTES RECEIVABLE, NET - Accounts and notes receivable and the allowance for doubtful debt (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2019USD ($)	Dec. 31, 2018CNY (¥)
ACCOUNTS AND NOTES RECEIVABLE, NET
Accounts receivable	¥ 913,902	$ 140,062	¥ 722,840
Notes receivable	2,252	345	2,146
Allowance for doubtful debt	(68,921)	(10,563)	(67,828)	$ (10,395)	¥ (70,970)
Accounts and notes receivable, net	¥ 847,233	$ 129,844	¥ 657,158

ACCOUNTS AND NOTES RECEIVABLE_4

ACCOUNTS AND NOTES RECEIVABLE, NET - Accounts and notes receivable due (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Balance at beginning of the year	¥ 67,828	$ 10,395	¥ 70,970
Additional provision charged to expense	2,393	367	485
Write-off of accounts receivable	(4,040)	(619)	(3,627)
Balance at end of the year	68,921	10,563	¥ 67,828
Cumulative Effect, Period of Adoption, Adjustment [Member]
Balance at end of the year	¥ 2,740	$ 420

SHORT-TERM INVESTMENTS - Short-

SHORT-TERM INVESTMENTS - Short-term investments consisted (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Short-term investments
SHORT-TERM INVESTMENTS
Time deposits	¥ 285,872	$ 43,812	¥ 363,856

SHORT-TERM INVESTMENTS - Additi

SHORT-TERM INVESTMENTS - Additional Information (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
Short-term investments
SHORT-TERM INVESTMENTS
Investments, interest income	¥ 5,712	$ 875	¥ 8,687	¥ 7,303

PREPAID EXPENSES AND OTHER CU_3

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
PREPAID EXPENSES AND OTHER CURRENT ASSETS
Prepaid expenses	¥ 884,156	$ 135,503	¥ 878,155
Tax recoverables	879,237	134,749	570,913
Deposits	31,774	4,870	17,391
Loan to third parties	19,107	2,928	73,557
Interest receivables	1,484	227	14,359
Staff advances	968	148	1,866
Others	49,458	7,580	61,908
Prepaid expenses and other current assets	¥ 1,866,184	$ 286,005	¥ 1,618,149

PROPERTY AND EQUIPMENT, NET - P

PROPERTY AND EQUIPMENT, NET - Property and equipment, held under capital leases (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
PROPERTY AND EQUIPMENT, NET
Property and equipment, gross	¥ 9,193,070	$ 1,408,900	¥ 6,065,200
Less: Accumulated depreciation	(3,285,138)	(503,469)	(2,514,800)
Impairment	(35,793)	(5,486)
Property plant and equipment net excluding construction in progress	5,872,139	899,945	3,550,400
Construction-in-progress	2,234,286	342,419	1,893,165
Property and equipment, net	8,106,425	1,242,364	5,443,565
Property
PROPERTY AND EQUIPMENT, NET
Property and equipment, gross	1,511,429	231,637	899,609
Leasehold improvements
PROPERTY AND EQUIPMENT, NET
Property and equipment, gross	2,609,828	399,974	1,458,749
Computer and network equipment
PROPERTY AND EQUIPMENT, NET
Property and equipment, gross	4,899,577	750,893	3,539,709
Optical Fibers
PROPERTY AND EQUIPMENT, NET
Property and equipment, gross	142,723	21,873	142,723
Office equipment
PROPERTY AND EQUIPMENT, NET
Property and equipment, gross	26,845	4,114	22,102
Motor vehicles
PROPERTY AND EQUIPMENT, NET
Property and equipment, gross	¥ 2,668	$ 409	¥ 2,308

PROPERTY AND EQUIPMENT, NET - D

PROPERTY AND EQUIPMENT, NET - Depreciation expense (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
PROPERTY AND EQUIPMENT, NET
Depreciation expense	¥ 908,387	$ 139,216	¥ 696,528	¥ 566,491
Cost of Revenues
PROPERTY AND EQUIPMENT, NET
Depreciation expense	850,746	130,382	644,108	520,791
Selling and Marketing Expense
PROPERTY AND EQUIPMENT, NET
Depreciation expense	2,399	368	2,107	986
General and Administrative Expense
PROPERTY AND EQUIPMENT, NET
Depreciation expense	29,711	4,553	30,110	28,727
Research and Development Expense
PROPERTY AND EQUIPMENT, NET
Depreciation expense	¥ 25,531	$ 3,913	¥ 20,203	¥ 15,987

PROPERTY AND EQUIPMENT, NET - C

PROPERTY AND EQUIPMENT, NET - Carrying amounts of property and equipment held under capital leases (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Lessee, Lease, Description [Line Items]
Property and equipment held under finance leases, gross	¥ 2,079,482	$ 318,695	¥ 1,147,387
Less: Accumulated depreciation	(661,796)	(101,425)	(408,196)
Property and equipment held under finance leases net excluding construction in progress	1,417,686	217,270	739,191
Construction-in-progress	2,234,286	342,419	1,893,165
Property and equipment held under finance leases, net	1,510,231	231,453	1,398,205
Property
Lessee, Lease, Description [Line Items]
Property and equipment held under finance leases, gross	921,970	141,298	365,353
Computer and network equipment
Lessee, Lease, Description [Line Items]
Property and equipment held under finance leases, gross	1,019,588	156,259	639,311
Optical Fibers
Lessee, Lease, Description [Line Items]
Property and equipment held under finance leases, gross	137,924	21,138	142,723
Construction-in-progress
Lessee, Lease, Description [Line Items]
Construction-in-progress	¥ 92,545	$ 14,183	¥ 659,014

PROPERTY AND EQUIPMENT, NET -_2

PROPERTY AND EQUIPMENT, NET - Property and equipment pledged to secure banking borrowings (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
PROPERTY AND EQUIPMENT, NET
Assets pledged as collateral	¥ 134,415	$ 20,600
Property
PROPERTY AND EQUIPMENT, NET
Assets pledged as collateral	264,784	40,580	¥ 137,585
Leasehold improvements
PROPERTY AND EQUIPMENT, NET
Assets pledged as collateral	90,947	13,938	¥ 66,162
Computer and network equipment
PROPERTY AND EQUIPMENT, NET
Assets pledged as collateral	40,871	6,264
Construction-in-progress
PROPERTY AND EQUIPMENT, NET
Assets pledged as collateral	¥ 238,771	$ 36,593

PROPERTY AND EQUIPMENT, NET - A

PROPERTY AND EQUIPMENT, NET - Additional Information (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
PROPERTY AND EQUIPMENT, NET
Depreciation expense	¥ 908,387	$ 139,216	¥ 696,528	¥ 566,491
Property, computer and network equipment and optical fiber
PROPERTY AND EQUIPMENT, NET
Depreciation expense	¥ 255,458	$ 39,151	¥ 216,664	¥ 170,264

INTANGIBLE ASSETS, NET - Intang

INTANGIBLE ASSETS, NET - Intangible assets (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
Weighted average useful lives of intangible assets
Beginning balance	¥ 410,595		¥ 355,313
Additions	363,189		124,697
Foreign currency translation difference	(4,245)		1,613
Amortization expense	(72,690)	$ (11,140)	(71,028)	¥ (68,115)
Impairment	(38,654)	(5,924)
Ending balance	658,195	100,873	410,595	355,313
Purchased software
Weighted average useful lives of intangible assets
Beginning balance	42,727		47,254
Additions	12,893		11,128
Foreign currency translation difference	(32)		413
Amortization expense	(13,689)		(16,068)
Ending balance	41,899	6,421	42,727	47,254
Radio Spectrum License
Weighted average useful lives of intangible assets
Beginning balance	65,123		72,908
Foreign currency translation difference	(4,213)		1,200
Amortization expense	(8,403)		(8,985)
Impairment	(38,654)
Ending balance	13,853	2,123	65,123	72,908
Operating permits
Weighted average useful lives of intangible assets
Beginning balance	97,244
Additions	274,904		100,380
Amortization expense	(5,189)		(3,136)
Ending balance	366,959	56,239	97,244
Contract Backlog
Weighted average useful lives of intangible assets
Beginning balance			5,162
Amortization expense			(5,162)
Ending balance		0		5,162
Customer Relationships
Weighted average useful lives of intangible assets
Beginning balance	88,040		112,961
Amortization expense	(24,854)		(24,921)
Ending balance	63,186	9,684	88,040	112,961
Licenses
Weighted average useful lives of intangible assets
Beginning balance	3,498		3,883
Amortization expense	(385)		(385)
Ending balance	3,113	477	3,498	3,883
Supplier Relationships
Weighted average useful lives of intangible assets
Beginning balance	13,996		17,070
Amortization expense	(3,074)		(3,074)
Ending balance	10,922	1,674	13,996	17,070
Trade Names
Weighted average useful lives of intangible assets
Beginning balance	84,778		90,591
Amortization expense	(5,813)		(5,813)
Ending balance	78,965	12,102	84,778	90,591
Customer Contract
Weighted average useful lives of intangible assets
Additions	66,708
Amortization expense	(3,602)
Ending balance	63,106	9,671
Non - Complete Agreement
Weighted average useful lives of intangible assets
Beginning balance			44
Amortization expense			(44)
Ending balance		0		44
Internal-use Software
Weighted average useful lives of intangible assets
Beginning balance	15,189		5,440
Additions	8,684		13,189
Amortization expense	(7,681)		(3,440)
Ending balance	¥ 16,192	$ 2,482	¥ 15,189	¥ 5,440

INTANGIBLE ASSETS, NET - Amorti

INTANGIBLE ASSETS, NET - Amortization expenses (Details) - Dec. 31, 2020 ¥ in Thousands, $ in Thousands	CNY (¥)	USD ($)
INTANGIBLE ASSETS, NET
2021	¥ 78,149	$ 11,977
2022	63,039	9,661
2023	41,574	6,371
2024	31,923	4,892
2025	27,424	4,203
Annual estimated amortization expenses for intangible assets	¥ 242,109	$ 37,104

INTANGIBLE ASSETS, NET - Additi

INTANGIBLE ASSETS, NET - Additional Information (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
Weighted average useful lives of intangible assets
Intangible assets, amortization expenses	¥ 72,690	$ 11,140	¥ 71,028	¥ 68,115
Minimum
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	1 year	1 year
Maximum
Weighted average useful lives of intangible assets
Estimated useful life of intangible assets	36 years	36 years

LAND USE RIGHTS, NET - Land use

LAND USE RIGHTS, NET - Land use rights amortized (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
LAND USE RIGHTS, NET
Cost	¥ 278,138	$ 42,627	¥ 249,804
Accumulated amortization	(22,765)	(3,489)	(16,650)
Land use rights, net	¥ 255,373	$ 39,138	¥ 233,154

LAND USE RIGHTS, NET - Land u_2

LAND USE RIGHTS, NET - Land use rights pledged (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
LAND USE RIGHTS, NET
Land use rights	¥ 141,000	$ 21,609	¥ 15,989

GOODWILL - Carrying amount (Det

GOODWILL - Carrying amount (Details) - 12 months ended Dec. 31, 2020 ¥ in Thousands, $ in Thousands	CNY (¥)	USD ($)
GOODWILL
Beginning Balance	¥ 989,530	$ 151,652
Additions	5,463	837
Ending Balance	¥ 994,993	$ 152,489

GOODWILL - Additional Informati

GOODWILL - Additional Information (Details) - CNY (¥) ¥ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Hosting and Related Services
Changes in the carrying amount of goodwill
Impairment losses of goodwill	¥ 0	¥ 0	¥ 0

LONG-TERM INVESTMENTS, NET - Lo

LONG-TERM INVESTMENTS, NET - Long term investments (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
LONG-TERM INVESTMENTS, NET
Equity investments without readily determinable fair values	¥ 17,137	$ 2,626	¥ 43,824
Equity method investments	116,667	17,880	124,116
Available-for-sale debt investments	1,713	263	1,713
Long term investments	¥ 135,517	$ 20,769	¥ 169,653

LONG-TERM INVESTMENTS, NET - Eq

LONG-TERM INVESTMENTS, NET - Equity Method Investments (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2019USD ($)	Dec. 31, 2018CNY (¥)
LONG-TERM INVESTMENTS
Cost investment	¥ 140,837		¥ 169,905		¥ 521,863
Share equity gain (loss)	(24,170)		(45,789)		(31,487)
Investment in an equity investee	116,667	$ 17,880	124,116	$ 124,116	490,376
Cost of investments incurred during the period	(29,068)		(351,958)
Share equity gain (loss) incurred during the period	10,274		(34,263)
Derecognize of share equity loss			19,961
Derecognize of share equity (gain) loss	11,345
Yizhuang Venture Investment Fund
LONG-TERM INVESTMENTS
Cost investment	101,000		101,000		101,000
Share equity gain (loss)	1,683		7,152		25,681
Investment in an equity investee	102,683	15,737	108,152	108,152	126,681
Share equity gain (loss) incurred during the period	12,254		1,671
Derecognize of share equity loss			(20,200)
Derecognize of share equity (gain) loss	(17,723)
Shihua DC Investment Holdings Limited
LONG-TERM INVESTMENTS
Cost investment			29,068		366,623
Share equity gain (loss)			(29,068)		(33,658)
Investment in an equity investee					332,965
Cost of investments incurred during the period	(29,068)		(337,555)
Share equity gain (loss) incurred during the period			(17,718)
Derecognize of share equity loss			22,308
Derecognize of share equity (gain) loss	29,068
Jingliang Inter Cloud
LONG-TERM INVESTMENTS
Cost investment	6,000		6,000		6,000
Share equity gain (loss)	(2,831)		(1,928)		(34)
Investment in an equity investee	3,169	486	4,072	4,072	5,966
Share equity gain (loss) incurred during the period	(903)		(1,894)
Jingliang Century Cloud
LONG-TERM INVESTMENTS
Cost investment	4,000		4,000		4,000
Investment in an equity investee	4,000	613	4,000	4,000	4,000
Huaye Cloud
LONG-TERM INVESTMENTS
Cost investment					23,333
Share equity gain (loss)					(6,319)
Investment in an equity investee					17,014
Cost of investments incurred during the period			(23,333)
Share equity gain (loss) incurred during the period			(11,534)
Derecognize of share equity loss			17,853
ZJK Energy
LONG-TERM INVESTMENTS
Cost investment	5,907		5,907		5,907
Share equity gain (loss)	(2,748)		(1,945)		(2,157)
Investment in an equity investee	3,159	484	3,962	3,962	3,750
Share equity gain (loss) incurred during the period	(803)		212
WiFire Group ("WiFire Group")
LONG-TERM INVESTMENTS
Cost investment	20,000		20,000		15,000
Share equity gain (loss)	(20,000)		(20,000)		¥ (15,000)
Cost of investments incurred during the period			5,000
Share equity gain (loss) incurred during the period			(5,000)
Chengdu Qidi Chengxin Education Limit ("Qidi Chengxin")
LONG-TERM INVESTMENTS
Cost investment	3,930		3,930
Share equity gain (loss)	(274)
Investment in an equity investee	3,656	$ 560	3,930	$ 3,930
Cost of investments incurred during the period			¥ 3,930
Share equity gain (loss) incurred during the period	¥ (274)

LONG-TERM INVESTMENTS, NET - Ad

LONG-TERM INVESTMENTS, NET - Additional Information (Details) ¥ in Thousands, $ in Thousands	1 Months Ended							12 Months Ended
	Dec. 31, 2019CNY (¥)	Nov. 30, 2019CNY (¥)	Mar. 31, 2018CNY (¥)	Jan. 31, 2018CNY (¥)	Sep. 30, 2017	Mar. 31, 2017CNY (¥)	Apr. 30, 2012CNY (¥)	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)	Dec. 31, 2020USD ($)
Schedule of Equity Method Investments [Line Items]
Impairment of investment								¥ 13,030	$ 1,997
Distribution received								17,723	2,716	¥ 20,200
Increase (Decrease) in Cost of Investments in Equity Method Investments								(29,068)		(351,958)
Disposal gain										17,853	¥ 16,509
Equity method investment loss								10,869	1,666	(50,553)	(186,642)
Equity method investment	¥ 124,116							116,667		124,116		$ 17,880
WiFire Group ("WiFire Group")
Schedule of Equity Method Investments [Line Items]
Equity interest, percentage					33.33%
Capital injected										5,000
Percentage of ownership disposed					66.67%
Equity method investment								0
Equity Investments Without Readily Determinable Fair Value
Schedule of Equity Method Investments [Line Items]
Equity investments without readily determinable fair values								13,500	2,069	13,122
Dividend income of non-marketable investments								607	93	461	406
Gain from disposal of non-marketable investments								257	39	5,536	20,496
Impairment of investment								¥ 13,030	1,997	¥ 0	¥ 0
Yizhuang Venture Investment Fund
Schedule of Equity Method Investments [Line Items]
Equity interest, percentage	27.694%							27.694%		27.694%	27.694%	27.694%
Distribution received								¥ 17,723	$ 2,716	¥ 20,200
Capital injected							¥ 101,000
Equity method investment loss										7,152
Shihua DC Investment Holdings Limited
Schedule of Equity Method Investments [Line Items]
Increase (Decrease) in Cost of Investments in Equity Method Investments								¥ (29,068)		(337,555)
Accumulative share equity loss derecognized	¥ 22,308									22,308
Shihua Investment Management [Member]
Schedule of Equity Method Investments [Line Items]
Equity interest, percentage						49.00%
Capital injected						¥ 13,537					¥ 15,531
Share equity loss recognized	¥ 16,290									¥ 16,290
Chengdu Qidi Chengxin Education Limit ("Qidi Chengxin")
Schedule of Equity Method Investments [Line Items]
Equity interest, percentage	59.00%									59.00%
Capital injected	¥ 3,930
Increase (Decrease) in Cost of Investments in Equity Method Investments										¥ 3,930
Shihua DC Investment Holdings 2 Limited ("Shihua Holdings 2")
Schedule of Equity Method Investments [Line Items]
Equity interest, percentage						49.00%
Capital injected						¥ 133,639					¥ 203,916
Jingliang Inter Cloud
Schedule of Equity Method Investments [Line Items]
Equity interest, percentage				60.00%
Capital injected				¥ 6,000
Jingliang Century Cloud
Schedule of Equity Method Investments [Line Items]
Equity interest, percentage				40.00%
Capital injected				¥ 4,000
Huaye Cloud
Schedule of Equity Method Investments [Line Items]
Equity interest, percentage			50.00%
Capital injected			¥ 23,333
Increase (Decrease) in Cost of Investments in Equity Method Investments										¥ (23,333)
Disposal gain		¥ 17,853
Total cash consideration on disposal of equity interests		23,333
Investment loss		¥ 17,853

BORROWINGS - Borrowings (Detail

BORROWINGS - Borrowings (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
BORROWINGS
Short-term bank borrowings	¥ 34,000	$ 5,211	¥ 234,500
Long-term bank borrowings, current portion	68,500	10,498	32,500
Other long-term borrowings, current portion	111,828	17,138
Borrowings, current portion, Total	214,328	32,847	267,000
Long-term bank borrowings, non-current portion	605,119	92,738	79,500
Other long-term borrowings, non-current portion	281,877	43,200
Total borrowings	¥ 1,101,324	$ 168,785	¥ 346,500

BORROWINGS - Unused loan facili

BORROWINGS - Unused loan facilities (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Debt Instrument
Short-term borrowings	¥ 34,000	$ 5,211	¥ 234,500
Long-term borrowings (including current portion)	1,067,324		112,000
Unsecured Borrowing
Debt Instrument
Short-term borrowings	34,000		34,500
Long-term borrowings (including current portion)	190,682
Secured by a Subsidiary's Fixed Assets and Land Use Right | Long Term Bank Borrowings
Debt Instrument
Long-term borrowings (including current portion)			112,000
Secured by restricted cash | Short-term bank borrowings 1
Debt Instrument
Short-term borrowings			¥ 200,000
Secured by subsidiary's property and equipment and land-use right | Long Term Bank Borrowings
Debt Instrument
Long-term borrowings (including current portion)	404,781
Secured by subsidiary's property and equipment and land-use right and a subsidiary stock | Long Term Bank Borrowings
Debt Instrument
Long-term borrowings (including current portion)	271,861
Secured by a subsidiary's stock and the restricted cash | Long Term Bank Borrowings
Debt Instrument
Long-term borrowings (including current portion)	100,000
Secured by a subsidiary's stock | Long Term Bank Borrowings
Debt Instrument
Long-term borrowings (including current portion)	¥ 100,000

BORROWINGS - Unused loan faci_2

BORROWINGS - Unused loan facilities (Parenthetical) (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2019USD ($)
Debt Instrument
Assets pledged as collateral	¥ 134,415	$ 20,600
Short-term bank borrowings 1 | Secured by restricted cash
Debt Instrument
Restricted cash			¥ 215,816
Long Term Bank Borrowings | Secured by a Subsidiary's Fixed Assets and Land Use Right | Fixed assets
Debt Instrument
Assets pledged as collateral			203,747
Long Term Bank Borrowings | Secured by a Subsidiary's Fixed Assets and Land Use Right | Land Use Rights [Member]
Debt Instrument
Assets pledged as collateral			15,989
Long Term Bank Borrowings | Secured by subsidiary's property and equipment and land-use right | Property and equipment
Debt Instrument
Assets pledged as collateral	505,004	77,395
Long Term Bank Borrowings | Secured by subsidiary's property and equipment and land-use right | Land Use Rights [Member]
Debt Instrument
Assets pledged as collateral	40,034	6,135
Long Term Bank Borrowings | Secured by subsidiary's property and equipment and land-use right and a subsidiary stock | Property and equipment
Debt Instrument
Assets pledged as collateral	130,369	19,980
Long Term Bank Borrowings | Secured by subsidiary's property and equipment and land-use right and a subsidiary stock | Land Use Rights [Member]
Debt Instrument
Assets pledged as collateral			¥ 100,966	$ 15,474
Long Term Bank Borrowings | Secured by a subsidiary's stock
Debt Instrument
Restricted cash	¥ 104,400	$ 16,000

BORROWINGS - Additional Informa

BORROWINGS - Additional Information (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Short and long term bank borrowings
Short-term bank borrowings, weighted average interest rate	4.46%	4.46%	4.56%
Short-term bank borrowings, term	1 year
Unused loan facilities (in RMB) or (in dollars)	¥ 1,574,556	$ 241,311	¥ 326,068
Long Term Bank Borrowings
Short and long term bank borrowings
Long-term bank borrowings, weighted average interest rate	5.61%	5.61%	5.28%

ACCRUED EXPENSES AND OTHER PA_3

ACCRUED EXPENSES AND OTHER PAYABLES (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
ACCRUED EXPENSES AND OTHER PAYABLES
Payables for purchase of property, equipment and software	¥ 1,148,742	$ 176,052	¥ 554,693
Payroll and welfare payables	204,732	31,377	179,195
Amounts due to the original shareholders for acquired entities	66,466	10,186
Payables for acquisitions	47,805	7,326	47,805
Accrued service fees	47,572	7,291	52,746
Payables for office supplies and utilities	38,485	5,898	24,562
Interest payables	37,799	5,793	58,961
Value-added tax and other taxes payable	10,473	1,605	14,523
Others	29,489	4,520	46,450
Accrued expenses and other payables	¥ 1,631,563	$ 250,048	¥ 978,935

LEASES - Weighted average remai

LEASES - Weighted average remaining lease term and discount rate (Details)	Dec. 31, 2020	Dec. 31, 2019
Weighted average remaining lease term:
Operating lease	12 years 2 months 12 days	9 years 4 months 24 days
Finance lease	14 years 7 months 6 days	15 years 3 months 18 days
Weighted average discount rate:
Operating lease	6.56%	6.09%
Finance lease	8.63%	8.43%

LEASES - Total lease cost (Deta

LEASES - Total lease cost (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
Finance lease cost:
Depreciation	¥ 255,458	$ 39,151	¥ 216,664
Interest expenses	130,196	19,953	120,185	¥ 79,935
Operating lease cost	478,805	73,380	214,795
Total lease cost	¥ 864,459	$ 132,484	¥ 551,644

LEASES - Other information rela

LEASES - Other information related to leases (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash payments for operating leases	¥ 477,189	$ 73,132	¥ 193,174
Financing cash payments for finance leases	¥ 376,232	$ 57,660	¥ 333,614

LEASES - Future lease payments

LEASES - Future lease payments under operating leases and finance leases (Details) - Dec. 31, 2020 ¥ in Thousands, $ in Thousands		CNY (¥)	USD ($)
Future lease payments under finance leases
2021		¥ 542,268	$ 83,106
2022		293,643	45,003
2023		195,320	29,934
2024		124,389	19,063
2025		95,054	14,568
2026 and thereafter		1,678,170	257,191
Total future lease payments		2,928,844	448,865
Less: Imputed interest		(1,286,619)	(197,183)
Present value of future lease payments	[1]	1,642,225	251,682
Future lease payments under operating leases
2021		415,892	63,738
2022		221,680	33,974
2023		146,115	22,393
2024		103,891	15,922
2025		70,494	10,804
2026 and thereafter		1,115,382	170,940
Total future lease payments		2,073,454	317,771
Less: Imputed interest		(728,543)	(111,654)
Present value of future lease payments	[1]	¥ 1,344,911	$ 206,117
[1]	*     Present value of future operating lease payments consisted of current portion of operating lease liabilities, non-current portion of operating lease liabilities and operating lease liabilities in amounts due to related parties, amounting to RMB452,272 (US$69,314), RMB645,499 (US$98,927) and RMB247,140 (US$37,876) for the year ended December 31, 2020, respectively.

LEASES - Additional information

LEASES - Additional information (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Cash paid for amounts included in the measurement of lease liabilities:
Current portion of operating lease liabilities	¥ 452,272	$ 69,314	¥ 437,817
Non-current portion of operating lease liabilities	645,499	98,927	579,102
Operating lease liabilities due to related parties	247,140	37,876
Current portion of finance lease liabilities	403,843	61,892	227,115
Non-current portion of finance lease liabilities	688,128	105,460	¥ 896,927
Finance lease liabilities due to related parties	¥ 550,254	$ 84,330

BONDS PAYABLE - Long-Term Borro

BONDS PAYABLE - Long-Term Borrowings, Including Bonds Payable, Bank and Other Borrowings (Detail) - Dec. 31, 2020 ¥ in Thousands, $ in Thousands	CNY (¥)	USD ($)
BONDS PAYABLE
2021	¥ 2,158,266	$ 330,769
2022	222,796	34,145
2023	152,544	23,378
2024	189,988	29,117
2025	125,244	19,194
2026 and thereafter	¥ 222,119	$ 34,041

BONDS PAYABLE - Additional Info

BONDS PAYABLE - Additional Information (Details) ¥ in Thousands, $ in Thousands	Aug. 04, 2020USD ($)	Aug. 12, 2019USD ($)	Apr. 16, 2019USD ($)	Apr. 15, 2019CNY (¥)	Dec. 31, 2019CNY (¥)	Apr. 15, 2019USD ($)
Debt Instrument
Loss on debt extinguishment | ¥					¥ 18,895
Bonds 7% Due 2020
Debt Instrument
Principal amount repurchased		$ 18,000	$ 150,839
Total aggregate principal amount repurchased (as a percent)			50.28%
Outstanding principal amount		$ 131,161
Principal amount repaid	$ (131,161)
Bonds 7.875%, Due 2021
Debt Instrument
Debt instrument, face amount						$ 300,000
Interest rate (as a percent)						7.875%
Proceeds from issuance of bonds, net | ¥				¥ 1,976,474

PERPETUAL CONVERTIBLE PREFERR_2

PERPETUAL CONVERTIBLE PREFERRED SHARES - Additional Information (Details) ¥ / shares in Units, $ / shares in Units, ¥ in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2020CNY (¥)¥ / shares	Dec. 31, 2020USD ($)$ / shares	Dec. 31, 2020USD ($)
Class of Stock [Line Items]
Total cash consideration		¥ 1,058,325	$ 162,195
Class A Ordinary Shares
Class of Stock [Line Items]
Number of shares issued | shares	150,000
Subscription price (in dollars per share)	$ 1,000
Dividend rate (as a percent)		4.50%	4.50%
Period after which Series A Preferred Shares will be mandatorily converted into Class A ordinary shares		6 months	6 months
Conversion price per share			$ 2.8333
Beneficial conversion feature		¥ 470,643	$ 72,129
American Depository Shares
Class of Stock [Line Items]
Total cash consideration | $	$ 150,000
Dividends declared | ¥ / shares		¥ 0
Cumulative dividends		¥ 22,806		$ 3,495
Conversion Threshold (as percent)		200.00%	200.00%
Conversion price per share			$ 17

CONVERTIBLE PROMISSORY NOTES (D

CONVERTIBLE PROMISSORY NOTES (Details)	1 Months Ended			12 Months Ended
	Dec. 31, 2020CNY (¥)shares	Dec. 31, 2020USD ($)shares	Aug. 31, 2020shares	Dec. 31, 2020CNY (¥)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2020USD ($)$ / shares
Debt Instrument [Line Items]
Term of the notes				1 year	1 year
Changes in the fair value of convertible promissory notes				¥ 2,544,220,000	$ 389,919,000
Convertible Notes Payable [Member]
Debt Instrument [Line Items]
Cash consideration received					$ 200,000
Term of the notes				5 years	5 years
Interest rate (as a percent)	2.00%			2.00%		2.00%
Issuance costs	¥ 2,939	$ 450		¥ 18,932	$ 2,901
Fair value of converted portion	720,547			720,547		$ 110,429
Fair value of notes	¥ 3,014,057			3,014,057		$ 461,924
Changes in the fair value of convertible promissory notes				¥ 2,544,220	389,919
Fair value changes related to instrument-specific risk					$ 0
Redemption upon maturity | Convertible Notes Payable [Member]
Debt Instrument [Line Items]
Redemption price, Percentage of principal amount redeemed				115.00%	115.00%
Early redemption at the option of the Purchasers | Convertible Notes Payable [Member]
Debt Instrument [Line Items]
Redemption price, Percentage of principal amount redeemed				109.00%	109.00%
American Depository Shares | Convertible Notes Payable [Member]
Debt Instrument [Line Items]
Conversion price (in dollars per share) | $ / shares						$ 12
Class A Ordinary Shares | Convertible Notes Payable [Member]
Debt Instrument [Line Items]
Number of shares issued upon conversion | shares	11,210,142	11,210,142	12,499,998	23,710,140	23,710,140

DEFERRED GOVERNMENT GRANTS - Mo

DEFERRED GOVERNMENT GRANTS - Movements of Deferred Grants (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
DEFERRED GOVERNMENT GRANTS
Balance at beginning of the year	¥ 8,501	$ 1,303	¥ 15,792	¥ 22,435
Additions				500
Recognized as a reduction of depreciation expense	(2,327)	(357)	(7,291)	(7,143)
Balance at end of the year	¥ 6,174	$ 946	¥ 8,501	¥ 15,792

DEFERRED GOVERNMENT GRANTS - Ad

DEFERRED GOVERNMENT GRANTS - Additional Information (Details) - CNY (¥) ¥ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
DEFERRED GOVERNMENT GRANTS
Government grants received	¥ 0	¥ 0	¥ 500

TREASURY STOCK (Details)

TREASURY STOCK (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
TREASURY STOCK
Share repurchase plan, shares repurchased (in shares)	0	242,830	0
American Depository Shares
TREASURY STOCK
Share repurchase plan, shares repurchased (in shares)	0	242,830	0

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
ACCUMULATED OTHER COMPREHENSIVE INCOME
Beginning balance	¥ 5,231,628		¥ 5,363,184	¥ 5,201,004
Current year other comprehensive income (loss)	(133,439)	$ (20,450)	(8,075)	88,652
Ending balance	6,897,480	1,057,085	5,231,628	5,363,184
Accumulated Translation Adjustment
ACCUMULATED OTHER COMPREHENSIVE INCOME
Beginning balance	77,904		85,979	(2,673)
Current year other comprehensive income (loss)	(133,439)		(8,075)	88,652
Ending balance	¥ (55,535)	$ (8,511)	¥ 77,904	¥ 85,979

MAINLAND CHINA EMPLOYEE CONTR_2

MAINLAND CHINA EMPLOYEE CONTRIBUTION PLAN (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
PRC
MAINLAND CHINA EMPLOYEE CONTRIBUTION PLAN
Total expense for defined contribution plan	¥ 77,982	$ 11,951	¥ 121,266	¥ 122,362

SHARE-BASED COMPENSATION - Empl

SHARE-BASED COMPENSATION - Employee share options activity (Details) - 2010 Plan $ / shares in Units, ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019$ / sharesshares	Dec. 31, 2020CNY (¥)shares
Number of options
Outstanding, beginning balance | shares	1,445,345
Exercised (in shares) | shares	(459,168)
Outstanding, ending balance | shares	508,866	1,445,345
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number | shares	508,866		508,866
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 0.33
Weighted average exercise price
Outstanding, beginning balance	0.51
Exercised	0.69
Outstanding, ending balance	0.33	$ 0.51
Vested and expected to vest at December 31, 2020	0.33
Exercisable, ending balance	$ 0.33
Weighted average remaining contractual term
Outstanding, December 31, 2019	9 months 18 days	1 year 3 months 18 days
Vested and expected to vest at December 31, 2020	9 months 18 days
Exercisable as of December 31, 2020	9 months 18 days
Aggregate intrinsic value
Outstanding, December 31, 2019	$ 2,774		¥ 18,100
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1 | $	$ 2,774

SHARE-BASED COMPENSATION - Rest

SHARE-BASED COMPENSATION - Restricted stock units activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
2010 Plan
Number of RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 0.53
Forfeited	(477,311)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 0.33
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	508,866
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$ 2,774
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 0.69
Restricted Stock Units (RSUs)
Number of RSUs
Unvested, beginning balance	2,696,129
Granted	2,163,543
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 22.62
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	8.91
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 6.59
Forfeited	(333,310)
Unvested, ending balance	4,092,457	2,696,129
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested	$ 141,967
Vested	(433,905)
Weighted-average grant date fair value
Unvested, beginning balance (in dollars per share)	$ 6.83
Unvested, ending balance (in dollars per share)	$ 14.95	$ 6.83
Weighted-average remaining contractual terms (Years)
Unvested, December 31, 2019	8 years 2 months 12 days	7 years 9 months 18 days

SHARE-BASED COMPENSATION - Shar

SHARE-BASED COMPENSATION - Share compensation expense (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
SHARE-BASED COMPENSATION
Share-based compensation expense	¥ 136,804	$ 20,966	¥ 43,916	¥ 59,538
Cost of Revenues
SHARE-BASED COMPENSATION
Share-based compensation expense	15,251	2,337	1,884	2,668
Selling and Marketing Expense
SHARE-BASED COMPENSATION
Share-based compensation expense	38,247	5,862	354	2,139
General and Administrative Expense
SHARE-BASED COMPENSATION
Share-based compensation expense	82,672	12,670	40,501	53,346
Research and Development Expense
SHARE-BASED COMPENSATION
Share-based compensation expense	¥ 634	$ 97	¥ 1,177	¥ 1,385

SHARE BASED COMPENSATION - Addi

SHARE BASED COMPENSATION - Additional Information (Details) $ / shares in Units, ¥ in Thousands, $ in Thousands	Oct. 30, 2015shares	Jul. 16, 2010shares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2020CNY (¥)shares	May 13, 2020shares	May 29, 2014shares
SHARE-BASED COMPENSATION
Aggregate intrinsic value of options exercise | $			$ 2,336	$ 22	$ 248
Performance Based Awards
SHARE-BASED COMPENSATION
Share based compensation, RSUs granted			314,842	464,120	487,368
Performance Based Awards | Option One
SHARE-BASED COMPENSATION
Performance review period			1 year
Performance Based Awards | Option Two
SHARE-BASED COMPENSATION
Performance review period			4 years
Restricted Stock Units (RSUs)
SHARE-BASED COMPENSATION
Share based compensation, RSUs granted			2,163,543
Aggregate fair value, unvested			$ 141,967			¥ 926,335
Weighted-average grant-date fair value | $ / shares			$ 22.62	$ 7.67	$ 6.39
Total fair value vested | $			$ 3,866	$ 6,185	$ 9,422
Unrecognized share-based compensation cost			$ 33,716			¥ 219,998
Unrecognized compensation costs, weighted-average recognition period			2 years 6 months
Minimum Performance Target
SHARE-BASED COMPENSATION
Share based compensation, RSUs granted			1,848,701	64,000	2,188,226
Market Based Awards
SHARE-BASED COMPENSATION
Share based compensation, RSUs granted			0	16,000	547,056
2014 Plan
SHARE-BASED COMPENSATION
Share based compensation, option expiry period	10 years
2014 Plan | Maximum
SHARE-BASED COMPENSATION
Share based compensation, maximum aggregate number of ordinary shares to be issued	39,606,817							20,461,380
Share based compensation, option vesting period	4 years
Share based compensation arrangement by share based payment award maximum annual plan percentage increase to number of shares available for grant	15.00%
2014 Plan | Minimum
SHARE-BASED COMPENSATION
Share based compensation, option vesting period	3 years
2010 Plan
SHARE-BASED COMPENSATION
Share based compensation, option expiry period		10 years
Share based compensation, option outstanding			508,866	1,445,345		508,866
Share based compensation, aggregate intrinsic value			$ 2,774			¥ 18,100
Share based compensation, fair value of option outstanding at grant date			922			¥ 6,014
Share based compensation, fair value of shares exercised during the period | $			$ 594	$ 42	$ 239
2010 Plan | Maximum
SHARE-BASED COMPENSATION
Share based compensation, maximum aggregate number of ordinary shares to be issued		39,272,595
Share based compensation, option vesting period		4 years
2010 Plan | Minimum
SHARE-BASED COMPENSATION
Share based compensation, option vesting period		3 years
2010 Plan and 2014 Plan | Class A Ordinary Shares
SHARE-BASED COMPENSATION
Shares reserved for future issuance under the plan							7,562,532
2020 Plan
SHARE-BASED COMPENSATION
Percentage of share capital considered for Maximum shares issuable under the plan							5.00%
Share based compensation, option outstanding			508,866			508,866
2020 Plan | Class A Ordinary Shares
SHARE-BASED COMPENSATION
Share based compensation, maximum aggregate number of ordinary shares to be issued							46,560,708

TAXATION - Income Taxes (Detail

TAXATION - Income Taxes (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
TAXATION
Loss before income taxes	¥ (2,570,923)	$ (394,010)	¥ (175,809)	¥ (162,325)
Non-PRC
TAXATION
Loss before income taxes	(2,708,101)	(415,033)	(178,762)	(214,063)
PRC
TAXATION
Loss before income taxes	¥ 137,178	$ 21,023	¥ 2,953	¥ 51,738

TAXATION - Income Tax Benefits

TAXATION - Income Tax Benefits (Expense) (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
TAXATION
Current	¥ (131,844)	$ (20,206)	¥ (70,324)	¥ (44,187)
Deferred	22,508	3,450	64,887	19,776
Income tax benefits (expenses)	¥ (109,336)	$ (16,756)	¥ (5,437)	¥ (24,411)

TAXATION - PRC operations (Deta

TAXATION - PRC operations (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
TAXATION
Loss before income taxes	¥ (2,570,923)	$ (394,010)	¥ (175,809)	¥ (162,325)
Income tax benefits computed at applicable tax rates (25%)	642,731	98,503	43,952	40,581
Non-deductible expenses	(4,117)	(631)	(23,082)	(2,834)
Research and development expenses	32,777	5,023	19,688	25,906
Preferential rate	26,554	4,070	20,213	11,701
Current and deferred tax rate differences	(36,391)	(5,577)	(8,699)	37,934
International rate differences	(711,962)	(109,113)	(77,066)	(63,525)
Tax exempted income	1,087	167	754
PRC withholding tax	(10,263)	(1,573)
Unrecognized tax benefits (expenses)	(58,449)	(8,958)	1,728	1,472
Change in valuation allowance	6,465	991	25,423	(79,694)
Prior year provision to return true up	2,232	342	(8,348)	4,048
Income tax expenses	¥ (109,336)	$ (16,756)	¥ (5,437)	¥ (24,411)

TAXATION - PRC operations (Pare

TAXATION - PRC operations (Parenthetical) (Details)	12 Months Ended			36 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
TAXATION
Statutory income tax rate	25.00%	25.00%	25.00%	25.00%

TAXATION - Deferred Taxes (Deta

TAXATION - Deferred Taxes (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Non-current
Allowance for doubtful debt	¥ 39,886	$ 6,113	¥ 48,568
Impairment of long-lived assets	13,467	2,064
Impairment of long-term investment	2,150	330
Accrued expense	24,986	3,829	21,139
Tax losses	171,211	26,239	146,996
Property and equipment	22,631	3,468	20,567
Intangible assets	5,765	884	3,691
Finance lease	390,925	59,912	395,555
Deferred government grant	1,357	208	1,189
Operating lease	292,210	44,783	269,468
Loss picked up on equity method investments	57,201	8,766	56,706
Valuation allowance	(170,104)	(26,070)	(158,638)
Total deferred tax assets	851,685	130,526	805,241
Non-current
Intangible assets	186,258	28,545	104,217
Property and equipment	143,873	22,050	81,424
Capitalized interest expenses	19,339	2,963	15,146
Finance lease	313,102	47,985	326,407
Operating lease	292,210	44,783	269,468
Investment in subsidiaries	10,263	1,573
Gain picked up from equity method investments	252	39	1,785
Total non-current deferred tax liabilities	965,297	147,938	798,447
Deferred tax assets	185,481	28,426	209,366
Deferred tax liabilities	299,093	45,838	202,572
Net deferred tax assets	113,612	17,412	¥ 6,794
Net deferred tax liabilities	¥ (113,612)	$ (17,412)

TAXATION - Unrecognized Tax Ben

TAXATION - Unrecognized Tax Benefits (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
TAXATION
Balance at beginning of year	¥ 1,722	$ 264	¥ 4,509
Reversal based on tax positions related to prior years	(629)	(96)	(3,266)
Additions based on tax positions related to the current year	61,491	9,423	479
Balance at end of year	¥ 62,584	$ 9,591	¥ 1,722

TAXATION - Additional Informati

TAXATION - Additional Information (Details) ¥ in Thousands, $ in Thousands	Jan. 01, 2008	Nov. 30, 2016	Oct. 31, 2015	Apr. 30, 2011	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)	Dec. 31, 2008	Dec. 31, 2020USD ($)
TAXATION
Unified enterprise income tax rate	25.00%
Undistributed earnings from its PRC subsidiaries					¥ 1,262,028					$ 193,414
Withholding tax liability					10,263	$ 1,573
Unrecognized tax benefits					68,696		¥ 2,443			10,528
Unrecognized tax benefits impact in the effective rate					¥ 58,916
Shanghai Blue Cloud Technology Co., Ltd. ("SH Blue Cloud")
TAXATION
Preferential tax rate			15.00%		15.00%	15.00%	15.00%	15.00%
Shenzhen Diyixian Telecommunication Co., Ltd. ("SZ DYX")
TAXATION
Preferential tax rate		15.00%			15.00%	15.00%	15.00%	15.00%
Preferential tax rate, additional term		3 years
Beijing 21Vianet Broad Band Data Center Co., Ltd. ("21Vianet Beijing")
TAXATION
Income tax rate								15.00%
Preferential tax rate					15.00%	15.00%	15.00%	15.00%	15.00%
21Vianet (Xi'an) Information Outsourcing Industry Park Services Co., Ltd. ("Xi'an Sub")
TAXATION
Preferential tax rate				15.00%	15.00%	15.00%	15.00%	15.00%
TAIWAN | DYX Taiwan
TAXATION
Income tax rate					20.00%	20.00%	20.00%	20.00%
PRC
TAXATION
Income tax rate on PRC tax resident enterprises					25.00%	25.00%
Net tax operating losses from PRC subsidiaries (in RMB)					¥ 710,815					108,937
Interest expenses (in RMB)					5,391	$ 826	¥ (1,447)	¥ (2,761)
Accumulated interest expenses (in RMB)					¥ 6,112		¥ 721			$ 937
PRC | Minimum
TAXATION
Net tax operating losses expiration year					2021	2021
PRC | Maximum
TAXATION
Net tax operating losses expiration year					2030	2030
HONG KONG | 21Vianet Hong Kong Entities
TAXATION
Income tax rate					16.50%	16.50%	16.50%	16.50%
Non-PRC
TAXATION
Withholding tax percent					10.00%	10.00%

RELATED PARTY TRANSACTIONS - Re

RELATED PARTY TRANSACTIONS - Related party transactions (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)	Dec. 31, 2020USD ($)
RELATED PARTY TRANSACTIONS
Related party transaction, loans from	¥ 51,007		¥ 166,935		$ 7,817
Jingliang Interconnected Cloud Technology Co Ltd | Service Revenue
RELATED PARTY TRANSACTIONS
Revenue from related party transactions	880	$ 135
Jingliang Interconnected Cloud Technology Co Ltd | Service Expense [Member]
RELATED PARTY TRANSACTIONS
Related party transaction expense	4,956	760	8,829	¥ 3,477
Beijing Tuspark Harmonious Investment Development Co Ltd
RELATED PARTY TRANSACTIONS
Related party transaction, loans from	13,557		24,917		2,078
Related party transaction, Lease deposit paid				11,472
Related party transaction, Lease payment paid	43,703	6,698	68,832
Xiaomi Communication Technology Limited and Beijing Xiaomi Mobile Software Limited | Service Revenue
RELATED PARTY TRANSACTIONS
Revenue from related party transactions	527,679	80,870	437,694	374,085
Beijing Kingsoft Cloud Network Technology Limited
RELATED PARTY TRANSACTIONS
Related party transaction expense	16,867	2,585	3,492	13,204
Related party transaction, loans from			1,073
Beijing Kingsoft Cloud Network Technology Limited | Service Revenue
RELATED PARTY TRANSACTIONS
Revenue from related party transactions	43	7	3,475	6,281
Dyxnet Corporate Service Limited | Service Expense [Member]
RELATED PARTY TRANSACTIONS
Related party transaction expense				5,238
Beijing Cheetah Mobile Technology Limited | Service Revenue
RELATED PARTY TRANSACTIONS
Revenue from related party transactions	98	15	169	2,079
Beijing Huaqing Property Management Co., Ltd | Service Expense [Member]
RELATED PARTY TRANSACTIONS
Related party transaction expense	4,389	673
Apurimac Partners Limited
RELATED PARTY TRANSACTIONS
Related party transaction, loans from	783				120
Apurimac Partners Limited | Service Expense [Member]
RELATED PARTY TRANSACTIONS
Related party transaction expense	8,124	1,245
Shanghai Puping
RELATED PARTY TRANSACTIONS
Related party transaction, loans to	62,531	9,583
Beijing Qidi Yefeng Investment Co., Ltd
RELATED PARTY TRANSACTIONS
Revenue from related party transactions	3,478	533	7,427
Related party transaction, loans from	4,410				676
Related party transaction, Lease payment paid	4,516	692
WiFire (Beijing) Technology Co., Ltd.
RELATED PARTY TRANSACTIONS
Related party transaction, loans from			6,330
WiFire (Beijing) Technology Co., Ltd. | Service Revenue
RELATED PARTY TRANSACTIONS
Revenue from related party transactions			1,934	16,490
WiFire (Beijing) Technology Co., Ltd. | Service Expense [Member]
RELATED PARTY TRANSACTIONS
Related party transaction expense				4,066
Beijing Taiji Data Tech Co Ltd
RELATED PARTY TRANSACTIONS
Revenue from related party transactions			7,899	13,681
Related party transaction, loans to			1,500
Beijing Taiji Data Tech Co Ltd | Service Expense [Member]
RELATED PARTY TRANSACTIONS
Related party transaction expense			19,942	7,095
Beijing Chengyishidai Network Technology Company Limited
RELATED PARTY TRANSACTIONS
Related party transaction expense	38,918	5,964	38,918	18,667
UNISVNET Technology Co Ltd | Service Revenue
RELATED PARTY TRANSACTIONS
Revenue from related party transactions				1,011
Other Related Party Transactions
RELATED PARTY TRANSACTIONS
Related party transaction, loans from	576		950		88
Other Related Party Transactions | Service Revenue
RELATED PARTY TRANSACTIONS
Revenue from related party transactions	305	47	1,494	4,493
Other Related Party Transactions | Service Expense [Member]
RELATED PARTY TRANSACTIONS
Related party transaction expense	796	122	5,866	6,396
Beijing Fastweb Network Technology Co Ltd Bjfastweb
RELATED PARTY TRANSACTIONS
Related party transaction, interest income from loan			700	700
Beijing Bozhi Ruihai Network Technology Co Ltd | Service Expense [Member]
RELATED PARTY TRANSACTIONS
Related party transaction expense				4,239
Ziguang Financial Leasing Co Ltd
RELATED PARTY TRANSACTIONS
Related party transaction, loans from	31,681		27,160		$ 4,855
Related party transaction, Lease deposit paid	135	21	6,154	2,042
Related party transaction, Lease payment paid	30,776	4,717	¥ 17,156	¥ 4,897
King Venture
RELATED PARTY TRANSACTIONS
Cash consideration for shares repurchase	¥ 130,472	19,996
Asialeads Capital (Cayman) Limited
RELATED PARTY TRANSACTIONS
Gross proceeds | $		$ 50,000

RELATED PARTY TRANSACTIONS - _2

RELATED PARTY TRANSACTIONS - Related party balances (Details) ¥ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Amounts due from related parties current:
Amounts due from related parties current	¥ 75,519	$ 11,574,000	¥ 301,665
Amounts due from related parties non-current:
Amounts due from related parties non current	20,562	3,151,000	20,654
Amounts due to related parties current:
Amount due to a related party	51,007	7,817,000	166,935
Amounts due from related parties non-current:
Amounts due to related parties non current	747,746	114,597,000	745,899
Marble Stone SH Group Limited ("Marble SH")
Amounts due from related parties current:
Amounts due from related parties current			100,106
Shihua DC Investment Group Limited ("Shihua Investment Group") [Member]
Amounts due from related parties current:
Amounts due from related parties current			82,542
Xiaomi Communication Technology Limited and Beijing Xiaomi Mobile Software Limited
Amounts due from related parties current:
Amounts due from related parties current			39,778
Marble Stone Holdings Limited ("Marble Holdings")
Amounts due from related parties current:
Amounts due from related parties current			29,736
Shihua DC Investment Management Limited ("Shihua Investment Management")
Amounts due from related parties current:
Amounts due from related parties current			27,905
Amounts due to related parties current:
Amount due to a related party			22,484
WiFire (Beijing) Technology Co., Ltd.
Amounts due to related parties current:
Amount due to a related party			6,330
Shanghai Shibei Hi-Tech Co., Ltd.
Amounts due from related parties current:
Amounts due from related parties current	9,800	1,502,000	9,800
Beijing Kingsoft Cloud Network Technology Limited
Amounts due to related parties current:
Amount due to a related party			1,073
Beijing Taiji Data Tech Co Ltd
Amounts due from related parties current:
Amounts due from related parties current			9,499
Qidi Bus (Beijing) Technology Co., Ltd
Amounts due from related parties current:
Amounts due from related parties current			1,249
Apurimac Partners Limited
Amounts due to related parties current:
Amount due to a related party	783	120,000
Other Related Party Transactions
Amounts due from related parties current:
Amounts due from related parties current	1,146	176,000	1,050
Amounts due from related parties non-current:
Amounts due from related parties non current	1,286	197,000	596
Amounts due to related parties current:
Amount due to a related party	576	88,000	950
Shanghai Puping
Amounts due from related parties current:
Amounts due from related parties current	62,531	9,583,000
Ziguang Financial Leasing Co Ltd
Amounts due from related parties non-current:
Amounts due from related parties non current	6,289	964,000	8,195
Amounts due to related parties current:
Amount due to a related party	31,681	4,855,000	27,160
Amounts due from related parties non-current:
Amounts due to related parties non current	22,247	3,409,000	47,388
Beijing Tuspark Harmonious Investment Development Co Ltd
Amounts due from related parties non-current:
Amounts due from related parties non current	11,863	1,818,000	11,863
Amounts due to related parties current:
Amount due to a related party	13,557	2,078,000	24,917
Amounts due from related parties non-current:
Amounts due to related parties non current	715,992	109,731,000	698,511
Shihua DC Investment Holdings Limited
Amounts due to related parties current:
Amount due to a related party			¥ 84,021
Ziguang Financial Leasing Co., Ltd
Amounts due from related parties current:
Amounts due from related parties current	2,042	313,000
Beijing Qidi Yefeng Investment Co., Ltd
Amounts due from related parties non-current:
Amounts due from related parties non current	1,124	172,000
Amounts due to related parties current:
Amount due to a related party	4,410	676,000
Amounts due from related parties non-current:
Amounts due to related parties non current	¥ 9,507	$ 1,457,000

RELATED PARTY TRANSACTIONS - Ad

RELATED PARTY TRANSACTIONS - Additional information (Details) ¥ in Thousands	12 Months Ended
	Dec. 31, 2019CNY (¥)
RELATED PARTY TRANSACTIONS
Impairment of amount due from equity investees	¥ 52,142
Shihua Holdings 2's subsidiaries
RELATED PARTY TRANSACTIONS
Equity interests acquired (as a percent)	100.00%
WiFire (Beijing) Technology Co., Ltd.
RELATED PARTY TRANSACTIONS
Amount due from/to related parties offset	¥ 20,367
Impairment of amount due from equity investees	¥ 52,142

RESTRICTED NET ASSETS (Details)

RESTRICTED NET ASSETS (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
RESTRICTED NET ASSETS
Minimum required Percentage of annual after-tax profit to the general statutory reserve	10.00%	10.00%
Maximum requirement of each of the Entity's PRC Subsidiaries' after-tax profits to be allocated to a general reserve fund as a percentage of each Subsidiaries' registered capital	50.00%	50.00%
Statutory reserves	¥ 74,462	$ 11,412	¥ 60,469
Restricted net asset, PRC generally accepted accounting principles (in RMB) or (in dollars)	¥ 9,885,573	$ 1,515,030

LOSS PER SHARE - Basic and dilu

LOSS PER SHARE - Basic and diluted loss per share (Details) ¥ / shares in Units, $ / shares in Units, ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)¥ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019CNY (¥)¥ / sharesshares	Dec. 31, 2018CNY (¥)¥ / sharesshares
Numerator:
Net loss	¥ (2,680,259)	$ (410,766)	¥ (181,246)	¥ (186,736)
Net profit attributable to noncontrolling interest	(29,088)	(4,458)	(1,046)	(18,329)
Net loss attributable to the Company	(2,709,347)	(415,224)	(182,292)	(205,065)
Plus undeclared cumulative dividend on perpetual convertible preferred shares	(22,806)	(3,495)
Deemed distribution to perpetual convertible preferred shareholders	(470,643)	(72,129)
Adjusted net loss attributable to ordinary shareholders	¥ (3,202,796)	$ (490,848)	¥ (182,292)	¥ (205,065)
Denominator:
Weighted average number of shares outstanding - basic (in shares)	716,888,919	716,888,919	668,833,756	674,732,130
Weighted average number of shares outstanding - diluted (in shares)	716,888,919	716,888,919	668,833,756	674,732,130
Loss per share-Basic:
Net loss | (per share)	¥ (4.47)	$ (0.69)	¥ (0.27)	¥ (0.30)
Basic (in per share) | (per share)	(4.47)	(0.69)	(0.27)	(0.30)
Loss per share-Diluted:
Net loss | (per share)	(4.47)	(0.69)	(0.27)	(0.30)
Diluted (in per share) | (per share)	¥ (4.47)	$ (0.69)	¥ (0.27)	¥ (0.30)

LOSS PER SHARE - Additional Inf

LOSS PER SHARE - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
LOSS PER SHARE
Shares issued to depository bank (in shares)	0	6,700,002	0

SHARE CAPITAL (Details)

SHARE CAPITAL (Details) $ / shares in Units, ¥ in Thousands, $ in Thousands	1 Months Ended				12 Months Ended
	Dec. 31, 2020Vote$ / sharesshares	Aug. 31, 2020CNY (¥)shares	Aug. 31, 2020USD ($)shares	Jun. 30, 2020$ / sharesshares	Dec. 31, 2020CNY (¥)shares	Dec. 31, 2020USD ($)Vote$ / sharesshares	Dec. 31, 2019CNY (¥)shares	Dec. 31, 2018shares	Oct. 31, 2019$ / sharesshares
SHARE CAPITAL
Proceeds from issuance of stock					¥ 2,680,421	$ 410,792	¥ 572
Convertible Notes Payable [Member]
SHARE CAPITAL
Percentage of total principal amount converted	23.70%					23.70%
Public offering
SHARE CAPITAL
Proceeds from issuance of stock		¥ 2,680,421	$ 410,792
Class A Ordinary Shares
SHARE CAPITAL
Entitled vote per ordinary share | Vote	1					1
Issuance of new shares for share option exercise and restricted share units vested							304,200	3,070,500
Number of shares repurchased and cancelled					104,304	104,304
Shares issued	1,199,790,000					1,199,790,000	1,200,000,000
Share Price | $ / shares				$ 1,000
Number of shares offered and sold				150,000
Class A Ordinary Shares | Convertible Notes Payable [Member]
SHARE CAPITAL
Number of shares issued upon conversion	11,210,142	12,499,998	12,499,998		23,710,140	23,710,140
Class A Ordinary Shares | Public offering
SHARE CAPITAL
Number of shares offered and sold		117,300,000	117,300,000
Class A Ordinary Shares | Over allotment option
SHARE CAPITAL
Number of shares offered and sold		15,300,000	15,300,000
Class B Ordinary Shares
SHARE CAPITAL
Entitled vote per ordinary share | Vote	10					10
Conversion share ratio	1					1
Shares issued	300,000,000					300,000,000	300,000,000
Class C Ordinary Shares
SHARE CAPITAL
Entitled vote per ordinary share | Vote	1					1
Conversion share ratio	1					1
Shares issued	60,000					60,000	60,000
Class C Ordinary Shares | Personal Group Limited
SHARE CAPITAL
Shares issued									60,000
Share Price | $ / shares									$ 1.35
American Depository Shares | Convertible Notes Payable [Member]
SHARE CAPITAL
Conversion price (in dollars per share) | $ / shares	$ 12					$ 12
American Depository Shares | Public offering
SHARE CAPITAL
Number of shares offered and sold		19,550,000	19,550,000
American Depository Shares | Over allotment option
SHARE CAPITAL
Number of shares offered and sold		2,550,000	2,550,000

FAIR VALUE MEASUREMENTS - Asset

FAIR VALUE MEASUREMENTS - Assets and liabilities measured (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	¥ 933,464	$ 143,060	¥ 483,394
Liabilities measured at fair value on recurring basis	5,012,145	768,144	3,003,639
Available-for-sales Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	1,713	263	1,713
Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities measured at fair value on recurring basis			2,089,114
Liability Classified RSU
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities measured at fair value on recurring basis			2,109
Current portion of bonds payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities measured at fair value on recurring basis	1,998,088	306,220	912,416
Convertible Notes Payable [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities measured at fair value on recurring basis	3,014,057	461,924
Bank Time Deposits | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	285,872	43,812	363,856
Bank Time Deposits | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	645,879	$ 98,985	117,825
Quoted prices in active markets for identical assets and liabilities (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	931,751		481,681
Liabilities measured at fair value on recurring basis	1,998,088		3,001,530
Quoted prices in active markets for identical assets and liabilities (Level 1) | Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities measured at fair value on recurring basis			2,089,114
Quoted prices in active markets for identical assets and liabilities (Level 1) | Current portion of bonds payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities measured at fair value on recurring basis	1,998,088		912,416
Quoted prices in active markets for identical assets and liabilities (Level 1) | Bank Time Deposits | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	285,872		363,856
Quoted prices in active markets for identical assets and liabilities (Level 1) | Bank Time Deposits | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	645,879		117,825
Unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	1,713		1,713
Liabilities measured at fair value on recurring basis	3,014,057		2,109
Unobservable inputs (Level 3) | Available-for-sales Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets measured at fair value on recurring basis	1,713		1,713
Unobservable inputs (Level 3) | Liability Classified RSU
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities measured at fair value on recurring basis			¥ 2,109
Unobservable inputs (Level 3) | Convertible Notes Payable [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities measured at fair value on recurring basis	¥ 3,014,057

FAIR VALUE MEASUREMENTS - Liabi

FAIR VALUE MEASUREMENTS - Liabilities measured (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2020USD ($)
Liability Classified RSU
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	¥ 2,109		¥ 4,970
Reclassification to equity	(2,109)		(2,861)
Ending Balance			2,109
Convertible Notes Payable [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance	1,409,385	$ 215,998
Foreign exchange loss	(219,001)			$ (33,564)
Changes in the fair value	2,544,220	389,919
Reclassification to equity	(720,547)	(110,429)
Ending Balance	¥ 3,014,057	$ 461,924	¥ 1,409,385

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Capital and purchase commitments (Details) - Dec. 31, 2020 ¥ in Thousands, $ in Thousands	CNY (¥)	USD ($)
Schedule of commitments to purchase certain computer and network equipment and construction-in-progress | Capital Commitments
Long-term Purchase Commitment [Line Items]
2021	¥ 1,678,273	$ 257,207
commitments to purchase	1,678,273	257,207
Schedule of outstanding purchase commitments in relation to bandwidth and cabinet capacity | Purchase commitment
Long-term Purchase Commitment [Line Items]
2021	706,715	108,309
2022	149,331	22,886
2023	6,458	990
2024	2,189	335
2025 and thereafter	6,512	998
commitments to purchase	¥ 871,205	$ 133,518

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Purchase Commitments (Details) - Dec. 31, 2020 - Purchase commitment - Schedule of outstanding purchase commitments in relation to bandwidth and cabinet capacity ¥ in Thousands, $ in Thousands	CNY (¥)	USD ($)
Long-term Purchase Commitment [Line Items]
2021	¥ 706,715	$ 108,309
2022	149,331	22,886
2023	6,458	990
2024	2,189	335
2025 and thereafter	¥ 6,512	$ 998

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Additional Information (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Oct. 30, 2020CNY (¥)	Oct. 30, 2020USD ($)	Apr. 09, 2018CNY (¥)
COMMITMENTS AND CONTINGENCIES
Accrual for unrecognized tax benefits and interest	¥ 68,696	$ 10,528
Estimated loss			¥ 1,628	$ 250
Securities Litigation
COMMITMENTS AND CONTINGENCIES
Litigation settlement amount					¥ 58,808

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 24, 2021	Mar. 01, 2021	Mar. 31, 2021	Jan. 31, 2021	Dec. 31, 2020	Feb. 29, 2020	Dec. 31, 2019
Subsequent Event
Term of the notes					1 year
Shares outstanding					150,000		0
Convertible Notes Payable [Member]
Subsequent Event
Total aggregate principal amount						$ 600,000
Simple interest rate					2.00%
Term of the notes					5 years
Subsequent Event | Convertible Notes Payable [Member]
Subsequent Event
Term of the notes				5 years
Subsequent Event | Series A Perpetual Convertible Preferred Shares
Subsequent Event
Shares outstanding		150,000
Subsequent Event | Class A Ordinary Shares
Subsequent Event
Shares converted		54,570,816
Subsequent Event | Class B Ordinary Shares
Subsequent Event
Number of shares to be repurchased			48,634,493
Share purchase price			$ 260,000
Share price per share			$ 5.346
Minimum percentage of shares retain under share repurchased agreement	5.00%
Subsequent Event | American Depository Shares
Subsequent Event
Share price per share			$ 32.076

PARENT COMPANY ONLY CONDENSED_3

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed balance sheets (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
Current assets
Cash and cash equivalents	¥ 2,710,349	$ 415,379	¥ 1,808,483	¥ 2,358,556
Short-term investments	285,872	43,812	363,856
Prepaid expenses and other current assets	1,866,184	286,005	1,618,149
Total current assets	6,055,607	928,062	5,228,184
Non-current assets
Total non-current assets	13,318,148	2,041,095	9,045,522
Total assets	19,373,755	2,969,157	14,273,706
Current liabilities:
Accrued expenses and other payables	1,631,563	250,048	978,935
Interest payable	37,799	5,793	58,961
Current portion of bonds payable	1,943,619	297,873	911,147
Total current liabilities	6,121,960	938,232	4,469,021
Non-current liabilities
Bonds payable			2,060,708
Convertible promissory notes	3,014,057	461,924
Total non-current liabilities	6,354,315	973,840	4,573,057
Total liabilities	12,476,275	1,912,072	9,042,078
Shareholders' equity:
Additional paid-in capital	13,083,119	2,005,076	9,202,567
Accumulated other comprehensive loss (income)	(55,535)	(8,511)	77,904
Accumulated deficit	(7,235,113)	(1,108,830)	(4,038,390)
Treasury stock	(349,523)	(53,567)	(349,523)
Total shareholders' equity	6,564,934	1,006,120	4,953,073
Total liabilities and shareholders' equity	19,373,755	2,969,157	14,273,706
Parent Company
Current assets
Cash and cash equivalents	62,116	9,520	243,989
Short-term investments			138,848
Prepaid expenses and other current assets	97,391	14,925	105,597
Amounts due from subsidiaries	9,320,580	1,428,441	6,128,595
Total current assets	9,480,087	1,452,886	6,617,029
Non-current assets
Investments in subsidiaries	2,169,222	332,448	1,446,563
Total non-current assets	2,169,222	332,448	1,446,563
Total assets	11,649,309	1,785,334	8,063,592
Current liabilities:
Accrued expenses and other payables	49,648	7,609	57,612
Account payables	52	8	56
Interest payable	37,353	5,725	58,525
Current portion of bonds payable	1,943,619	297,873	911,147
Amount due to related parties	783	120
Amounts due to subsidiaries	38,863	5,955	22,471
Total current liabilities	2,070,318	317,290	1,049,811
Non-current liabilities
Bonds payable			2,060,708
Total non-current liabilities	3,014,057	461,924	2,060,708
Total liabilities	5,084,375	779,214	3,110,519
Shareholders' equity:
Additional paid-in capital	13,083,119	2,005,076	9,202,567
Accumulated other comprehensive loss (income)	(55,535)	(8,511)	77,904
Accumulated deficit	(7,160,651)	(1,097,418)	(3,977,921)
Treasury stock	(349,523)	(53,567)	(349,523)
Total shareholders' equity	6,564,934	1,006,120	4,953,073
Total liabilities and shareholders' equity	11,649,309	1,785,334	8,063,592
Class A Ordinary Shares
Shareholders' equity:
Ordinary shares	44	7	34
Class A Ordinary Shares | Parent Company
Shareholders' equity:
Ordinary shares	44	7	34
Class B Ordinary Shares
Shareholders' equity:
Ordinary shares	12	2	12
Class B Ordinary Shares | Parent Company
Shareholders' equity:
Ordinary shares	12	2	¥ 12
Series A Perpetual Convertible Preferred Shares
Shareholders' equity:
Ordinary shares	¥ 1,047,468	$ 160,531

PARENT COMPANY ONLY CONDENSED_4

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed balance sheets (Parenthetical) (Details) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Class A Ordinary Shares
Condensed balance sheets
Ordinary shares, par value (in dollars per share)	$ 0.00001
Ordinary shares, shares authorized (in shares)	1,199,790,000	1,200,000,000
Ordinary shares, shares issued (in shares)	672,024,600	505,253,850
Ordinary shares, shares outstanding (in shares)	672,024,600	505,253,850
Class B Ordinary Shares
Condensed balance sheets
Ordinary shares, par value (in dollars per share)	$ 0.00001	$ 0.00001
Ordinary shares, shares authorized (in shares)	300,000,000	300,000,000
Ordinary shares, shares issued (in shares)	145,875,113	174,649,638
Ordinary shares, shares outstanding (in shares)	145,875,113	174,649,638
Class C Ordinary Shares
Condensed balance sheets
Ordinary shares, par value (in dollars per share)	$ 0.00001
Ordinary shares, shares authorized (in shares)	60,000	60,000
Ordinary shares, shares issued (in shares)	60,000	60,000
Ordinary shares, shares outstanding (in shares)	60,000	60,000
Series A Perpetual Convertible Preferred Shares
Condensed balance sheets
Ordinary shares, shares issued (in shares)	150,000
Ordinary shares, shares outstanding (in shares)	150,000
Parent Company | Class A Ordinary Shares
Condensed balance sheets
Ordinary shares, par value (in dollars per share)	$ 0.00001	$ 0.00001
Ordinary shares, shares authorized (in shares)	1,199,790,000	1,200,000,000
Ordinary shares, shares issued (in shares)	672,024,600	505,253,850
Ordinary shares, shares outstanding (in shares)	672,024,600	505,253,850
Parent Company | Class B Ordinary Shares
Condensed balance sheets
Ordinary shares, shares authorized (in shares)	300,000,000	300,000,000
Ordinary shares, shares issued (in shares)	145,875,113	174,649,638
Ordinary shares, shares outstanding (in shares)	145,875,113	174,649,638
Parent Company | Class C Ordinary Shares
Condensed balance sheets
Ordinary shares, par value (in dollars per share)	$ 0.00001	$ 0.00001
Ordinary shares, shares authorized (in shares)	60,000	60,000
Ordinary shares, shares issued (in shares)	60,000	60,000
Ordinary shares, shares outstanding (in shares)	60,000	60,000
Parent Company | Series A Perpetual Convertible Preferred Shares
Condensed balance sheets
Ordinary shares, par value (in dollars per share)	$ 0.00001

PARENT COMPANY ONLY CONDENSED_5

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION- Condensed statements of operations (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
Operating Expenses
General and administrative expenses	¥ (535,111)	$ (82,009)	¥ (415,277)	¥ (462,637)
Changes in the fair value of contingent purchase consideration payables				13,905
Operating loss	116,604	17,871	182,234	237,479
Changes in the fair value of convertible promissory notes	(2,544,220)	(389,919)
Loss before income taxes	(2,570,923)	(394,010)	(175,809)	(162,325)
Comprehensive loss attributable to 21Vianet Group, Inc.	(2,842,786)	(435,674)	(190,367)	(116,413)
Income tax expenses	(109,336)	(16,756)	(5,437)	(24,411)
Net loss attributable to the 21Vianet Group, Inc.	(2,709,347)	(415,224)	(182,292)	(205,065)
Parent Company
Operating Expenses
General and administrative expenses	(94,175)	(14,433)	(44,490)	(65,949)
Changes in the fair value of contingent purchase consideration payables				13,905
Operating loss	(94,175)	(14,433)	(44,490)	(52,044)
Other loss	(168,656)	(25,846)	(274,572)	(262,186)
Changes in the fair value of convertible promissory notes	(2,544,220)	(389,919)
Share of profits from subsidiaries and Consolidated VIEs	97,704	14,974	136,770	109,165
Loss before income taxes	(2,709,347)	(415,224)	(182,292)	(205,065)
Comprehensive loss attributable to 21Vianet Group, Inc.		(435,674)	(190,367)	(116,413)
Income tax expenses	0	0	0	0
Net loss attributable to the 21Vianet Group, Inc.	(2,709,347)	$ (415,224)	¥ (182,292)	¥ (205,065)
Reportable Legal Entities [Member] | Parent Company
Operating Expenses
Comprehensive loss attributable to 21Vianet Group, Inc.	(2,842,786)
Net loss attributable to the 21Vianet Group, Inc.	¥ (2,709,347)

PARENT COMPANY ONLY CONDENSED_6

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Statement of Comprehensive Loss (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
Condensed statements of comprehensive loss
Net loss	¥ (2,709,347)	$ (415,224)	¥ (182,292)	¥ (205,065)
Other comprehensive income (loss), net of tax of nil
Foreign currency translation adjustments, net of tax of nil	(133,439)	(20,450)	(8,075)	88,652
Comprehensive loss	(2,813,698)	(431,216)	(189,321)	(98,084)
Comprehensive loss attributable to 21Vianet Group, Inc.	(2,842,786)	(435,674)	(190,367)	(116,413)
Parent Company
Condensed statements of comprehensive loss
Net loss	(2,709,347)	(415,224)	(182,292)	(205,065)
Other comprehensive income (loss), net of tax of nil
Foreign currency translation adjustments, net of tax of nil		(20,450)	(8,075)	88,652
Other comprehensive income (loss), net of tax of nil:		(20,450)	(8,075)	88,652
Comprehensive loss		(435,674)	(190,367)	(116,413)
Comprehensive loss attributable to 21Vianet Group, Inc.		$ (435,674)	¥ (190,367)	¥ (116,413)
Reportable Legal Entities [Member] | Parent Company
Condensed statements of comprehensive loss
Net loss	(2,709,347)
Other comprehensive income (loss), net of tax of nil
Foreign currency translation adjustments, net of tax of nil	(133,439)
Other comprehensive income (loss), net of tax of nil:	(133,439)
Comprehensive loss	(2,842,786)
Comprehensive loss attributable to 21Vianet Group, Inc.	¥ (2,842,786)

PARENT COMPANY ONLY CONDENSED_7

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Statement of Comprehensive Loss (Parenthetical) (Details) - CNY (¥) ¥ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed statements of comprehensive loss
Foreign currency translation adjustments, tax	¥ 0	¥ 0	¥ 0
Parent Company
Condensed statements of comprehensive loss
Other comprehensive (loss) income, tax		0	0
Foreign currency translation adjustments, tax		¥ 0	¥ 0

PARENT COMPANY ONLY CONDENSED_8

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)	Dec. 31, 2018CNY (¥)
Condensed Cash Flow Statements, Captions
Net cash used in operating activities	¥ 714,243	$ 109,464	¥ 802,922	¥ 704,966
Net cash used in investing activities	(3,889,174)	(596,043)	(1,611,983)	(304,846)
Net cash generated from financing activities	4,163,255	638,046	461,557	(19,901)
Net increase (decrease) in cash and cash equivalents and restricted cash	759,260	116,361	(303,844)	465,552
Cash and cash equivalents and restricted cash at beginning of the year	2,357,177	361,253	2,661,021	2,195,469
Cash and cash equivalents and restricted cash at end of the year	3,116,437	477,614	2,357,177	2,661,021
Parent Company
Condensed Cash Flow Statements, Captions
Net cash used in operating activities	(743,944)	(114,014)	(142,989)	(166,068)
Net cash used in investing activities	(3,036,370)	(465,344)	(1,011,257)	(203,651)
Net cash generated from financing activities	3,598,441	551,485	807,765	43,145
Net increase (decrease) in cash and cash equivalents and restricted cash	(181,873)	(27,873)	(346,481)	(326,574)
Cash and cash equivalents and restricted cash at beginning of the year	243,989	37,393	590,470	917,044
Cash and cash equivalents and restricted cash at end of the year	¥ 62,116	$ 9,520	¥ 243,989	¥ 590,470

PARENT COMPANY ONLY CONDENSED_9

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Related Party transactions (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020CNY (¥)	Dec. 31, 2020USD ($)	Dec. 31, 2019CNY (¥)
Amount due from related parties current
Amount due from related parties current	¥ 75,519	$ 11,574	¥ 301,665
Amount due to related parties
Amounts due to related parties of the consolidated VIEs without resource to the primary beneficiaries	51,007	7,817	166,935
Parent Company
Amount due from subsidiaries current
Amount due from subsidiaries current	9,320,580	1,428,441	6,128,595
Amounts due to subsidiaries
Amount due to subsidiaries current	38,863	5,955	22,471
Parent Company | 21Vianet Hong Kong Entities
Amount due from subsidiaries current
Amount due from subsidiaries current	7,043,586	1,079,477	5,855,452
Parent Company | Hong Kong Fastweb Holdings Co., Limited ("Fastweb HK")
Amount due from subsidiaries current
Amount due from subsidiaries current	62,780	9,621	67,088
Parent Company | 21Vianet Mobile Limited ("21V Mobile")
Amount due from subsidiaries current
Amount due from subsidiaries current	56,265	8,623	58,018
Parent Company | WiFire Open Network Group Ltd
Amount due from subsidiaries current
Amount due from subsidiaries current	2,157,285	330,618	147,326
Parent Company | WiFire Group ("WiFire Group")
Amount due from subsidiaries current
Amount due from subsidiaries current	652	100	698
Parent Company | Other Subsidiaries
Amount due from subsidiaries current
Amount due from subsidiaries current	12	2	13
Amounts due to subsidiaries
Amount due to subsidiaries current	3,080	471	3,022
Parent Company | Beijing 21Vianet Zhi Hui Neng Yuan System Technology Company Limited
Amounts due to subsidiaries
Amount due to subsidiaries current	¥ 35,783	$ 5,484	¥ 19,449