Slack (WORK) 10-K 12 Mar 20 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Billions	12 Months Ended
	Jan. 31, 2020	Feb. 29, 2020	Jul. 31, 2019
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Jan. 31, 2020
Document Transition Report	false
Entity File Number	001-38926
Entity Registrant Name	Slack Technologies, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-4400325
Entity Address, Address Line One	500 Howard Street
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94105
City Area Code	415
Local Phone Number	630-7943
Title of 12(b) Security	Class A Common Stock, $0.0001 par value per share
Trading Symbol	WORK
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Public Float			$ 7.2
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement relating to the Annual Meeting of Stockholders are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. Such definitive Proxy Statement will be filed with the Securities and Exchange Commission within 120 days after the end of the registrant’s fiscal year ended January 31, 2020.
Entity Central Index Key	0001764925
Current Fiscal Year End Date	--01-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Class A Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		362,046,257
Class B Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		194,761,524

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Current assets:
Cash and cash equivalents	$ 498,999	$ 180,770
Marketable securities	269,593	660,301
Accounts receivable, net	145,844	87,438
Prepaid expenses and other current assets	55,967	54,213
Total current assets	970,403	982,722
Restricted cash	38,490	20,490
Strategic investments	28,814	12,334
Property and equipment, net	102,340	88,359
Operating lease right-of-use assets	197,830
Intangible assets, net	13,530	15,203
Goodwill	48,598	48,598
Other assets	41,701	31,250
Total assets	1,441,706	1,198,956
Current liabilities:
Accounts payable	16,893	16,613
Operating lease liability	30,465
Accrued compensation and benefits	65,196	46,151
Accrued expenses and other current liabilities	32,123	29,809
Deferred revenue	375,263	239,825
Total current liabilities	519,940	332,398
Operating lease liability, noncurrent	196,378
Deferred revenue, noncurrent	1,451	2,048
Other liabilities	38	22,904
Total liabilities	717,807	357,350
Commitments and contingencies (Note 10)
Stockholders’ equity:
Convertible preferred stock	0	1,392,101
Common stock	56	13
Additional paid-in-capital	1,945,446	105,633
Accumulated other comprehensive loss	(71)	(498)
Accumulated deficit	(1,236,621)	(665,563)
Total Slack Technologies, Inc. stockholders’ equity	708,810	831,686
Noncontrolling interest	15,089	9,920
Total stockholders’ equity	723,899	841,606
Total liabilities and stockholders’ equity	$ 1,441,706	$ 1,198,956

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Convertible preferred stock, shares authorized (in shares)	100,000,000
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible Preferred Stock
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized (in shares)	0	390,589,000
Convertible preferred stock, shares issued (in shares)	0	373,372,000
Convertible preferred stock, shares outstanding (in shares)	0	373,372,000
Convertible preferred stock, liquidation preference	$ 0	$ 1,389,925
Class A Common Stock
Common stock, shares authorized (in shares)	5,000,000,000	660,000,000
Common stock, shares issued (in shares)	360,557,000	896,000
Common stock, shares outstanding (in shares)	360,557,000	896,000
Class B Common Stock
Common stock, shares authorized (in shares)	700,000,000	650,000,000
Common stock, shares issued (in shares)	194,803,000	126,677,000
Common stock, shares outstanding (in shares)	194,803,000	126,677,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Income Statement [Abstract]
Revenue	$ 630,422	$ 400,552	$ 220,544
Cost of revenue	97,191	51,301	26,364
Gross profit	533,231	349,251	194,180
Operating expenses:
Research and development	457,364	157,538	141,350
Sales and marketing	402,780	233,191	140,188
General and administrative	261,365	112,730	56,493
Total operating expenses	1,121,509	503,459	338,031
Loss from operations	(588,278)	(154,208)	(143,851)
Other income (expense), net	20,510	16,146	4,581
Loss before income taxes	(567,768)	(138,062)	(139,270)
Provision for income taxes	589	840	793
Net loss	(568,357)	(138,902)	(140,063)
Net income attributable to noncontrolling interest	2,701	1,781	22
Net loss attributable to Slack	(571,058)	(140,683)	(140,085)
Less: Deemed dividends to preferred stockholders	0	0	40,883
Net loss attributable to Slack common stockholders	$ (571,058)	$ (140,683)	$ (180,968)
Basic and diluted net loss per share:
Net loss per share attributable to Slack common stockholders, basic and diluted (in dollars per share)	$ (1.43)	$ (1.16)	$ (1.47)
Weighted-average shares used in computing net loss per share attributable to Slack common stockholders, basic and diluted (in shares)	399,461	121,732	122,865

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (568,357)	$ (138,902)	$ (140,063)
Other comprehensive income (loss), net of tax:
Change in unrealized gain or loss on marketable securities	427	591	(677)
Other comprehensive income (loss), net of tax	427	591	(677)
Comprehensive loss	(567,930)	(138,311)	(140,740)
Comprehensive income attributable to noncontrolling interest	2,701	1,781	22
Comprehensive loss attributable to Slack	$ (570,631)	$ (140,092)	$ (140,762)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Restricted stock units	Series G Preferred Stock	Series G-1 Preferred Stock	Series G-2 Preferred Stock	Series G-3 Preferred Stock	Class B Common Stock	Series A Preferred Stock	Series D Preferred Stock	Series D-1 Preferred Stock	Series E Preferred Stock	Series H Preferred Stock	Series H-1 Preferred Stock	Convertible Preferred Stock	Convertible Preferred StockSeries G Preferred Stock	Convertible Preferred StockSeries G-1 Preferred Stock	Convertible Preferred StockSeries G-2 Preferred Stock	Convertible Preferred StockSeries G-3 Preferred Stock	Convertible Preferred StockSeries A Preferred Stock	Convertible Preferred StockSeries D Preferred Stock	Convertible Preferred StockSeries D-1 Preferred Stock	Convertible Preferred StockSeries E Preferred Stock	Convertible Preferred StockSeries H Preferred Stock	Convertible Preferred StockSeries H-1 Preferred Stock	Common Stock	Common StockRestricted stock awards	Common StockRestricted stock units	Common StockClass B Common Stock	Additional Paid-In-Capital	Additional Paid-In-CapitalRestricted stock units	Additional Paid-In-CapitalClass B Common Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit	Accumulated DeficitClass B Common Stock	Accumulated DeficitSeries A Preferred Stock	Accumulated DeficitSeries D Preferred Stock	Accumulated DeficitSeries D-1 Preferred Stock	Accumulated DeficitSeries E Preferred Stock	Noncontrolling Interest
Beginning of period (in shares) at Jan. 31, 2017														301,197											125,678
Beginning of period at Jan. 31, 2017	$ 353,082													$ 589,709											$ 13				$ 60,766			$ (412)	$ (305,111)						$ 8,117
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)																									3,662
Exercise of stock options	3,634																								$ 0				3,634
Vesting of early exercised stock options	480																												480
Issuance of stock (in shares)															24,718	2,149	17,241	1,465
Issuance of stock			$ 229,648	$ 20,000	$ 150,000	$ 12,714									$ 229,648	$ 20,000	$ 150,000	$ 12,714
Repurchase of stock (in shares)																			(458)	(4,568)	(75)	(4,186)						(9,605)
Repurchase of stock							$ (40,506)	$ (3,831)	$ (38,239)	$ (630)	$ (35,033)								$ (44)	$ (11,650)	$ (156)	$ (25,000)						$ (1)			$ (1,704)			$ (38,801)	$ (3,787)	$ (26,589)	$ (474)	$ (10,033)
Other comprehensive income (loss)	(677)																															(677)
Stock-based compensation	8,709																												8,709
Net income (loss)	(140,063)																																(140,085)						22
End of period (in shares) at Jan. 31, 2018														337,483											119,735
End of period at Jan. 31, 2018	519,288													$ 965,221											$ 12				71,885			(1,089)	(524,880)						8,139
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)																									4,888
Exercise of stock options	4,167																								$ 1				4,166
Vesting of early exercised stock options	366																												366
Issuance of restricted stock awards (in shares)																										2,197
Issuance of stock (in shares)																							33,470	2,419	900
Issuance of stock	6,084											$ 398,082	$ 28,798										$ 398,082	$ 28,798					6,084
Cancellation of restricted stock awards (RSAs) (in shares)																										(19)
Repurchase of stock (in shares)																									(128)
Other comprehensive income (loss)	591																															591
Stock-based compensation	23,132																												23,132
Net income (loss)	(138,902)																																(140,683)						1,781
End of period (in shares) at Jan. 31, 2019														373,372											127,573
End of period at Jan. 31, 2019	$ 841,606													$ 1,392,101											$ 13				105,633			(498)	(665,563)						9,920
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	13,268																								13,268
Exercise of stock options	$ 13,620																								$ 1				13,619
Vesting of early exercised stock options	260																												260
Issuance of restricted stock awards (in shares)																										505
Issuance of stock (in shares)																											40,318
Cancellation of restricted stock awards (RSAs) (in shares)																										(10)
Repurchase of stock (in shares)																									(2)
Conversion of convertible preferred stock to common stock in connection with direct listing (in shares)														(373,372)											373,372
Conversion of convertible preferred stock to common stock in connection with direct listing	0													$ (1,392,101)											$ 38				1,392,063
Issuance of common stock upon settlement of restricted stock units (RSUs)		$ 0																									$ 4			$ (4)
Issuance of common stock for employee share purchase plan (in shares)																									336
Issuance of common stock for employee share purchase plan	7,351																												7,351
Capital contributions from noncontrolling interest holders	3,840																																						3,840
Distributions to noncontrolling interest holders	(1,372)																																						(1,372)
Other comprehensive income (loss)	427																															427
Stock-based compensation	426,524																												426,524
Net income (loss)	(568,357)																																(571,058)						2,701
End of period (in shares) at Jan. 31, 2020														0											555,360
End of period at Jan. 31, 2020	$ 723,899													$ 0											$ 56				$ 1,945,446			$ (71)	$ (1,236,621)						$ 15,089

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Cash flows from operating activities:
Net loss	$ (568,357)	$ (138,902)	$ (140,063)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	27,127	16,816	14,320
Loss on disposal of property and equipment	39	2,281	0
Stock-based compensation	426,524	23,132	8,709
Non-cash operating lease expense	8,963
Amortization of deferred contract acquisition costs	8,153	3,154	611
Net amortization of bond premium (discount) debt securities available for sale	(2,180)	(3,057)	1,352
Change in fair value of strategic investments	(5,599)	(3,701)	(27)
Other non-cash charges	(249)	546	366
Changes in operating assets and liabilities:
Accounts receivable	(58,202)	(50,305)	(21,964)
Prepaid expenses and other assets	(20,594)	(53,072)	6,362
Accounts payable	6,726	2,846	4,851
Operating lease liabilities	(9,495)
Accrued compensation and benefits	19,045	22,504	12,470
Deferred revenue	134,841	116,420	68,469
Other current and long-term liabilities	20,869	20,279	8,927
Net cash used in operating activities	(12,389)	(41,059)	(35,617)
Cash flows from investing activities:
Purchases of marketable securities	(290,188)	(967,055)	(510,755)
Maturities of marketable securities	517,583	727,616	278,263
Sales of marketable securities	166,074	11,271	16,934
Acquisitions of businesses, net of cash acquired	0	(45,313)	0
Acquisition of intangible assets	(2,500)	(2,382)	0
Purchases of property and equipment	(49,626)	(56,180)	(22,044)
Sales of property and equipment	0	762	0
Capitalized software development costs	0	(840)	(50)
Purchase of strategic investments	(14,132)	(2,276)	(2,901)
Proceeds from liquidation of strategic investments	2,917	976	117
Net cash provided by (used in) investing activities	330,128	(333,421)	(240,436)
Cash flows from financing activities:
Proceeds from exercise of stock options	14,227	4,783	2,912
Repurchase of common stock	0	0	(40,506)
Payment of contingent consideration for an acquisition	(5,000)	0	0
Issuance of common stock for employee stock purchase plan	7,351	0	0
Net proceeds from issuance of convertible preferred stock	0	426,880	412,362
Repurchase of convertible preferred stock	0	0	(77,733)
Capital contributions from noncontrolling interest holders	3,840	0	0
Distributions to noncontrolling interest holders	(1,372)	0	0
Issuance of common stock to third party	0	6,084	0
Other financing activities	(556)	(70)	0
Net cash provided by financing activities	18,490	437,677	297,035
Net increase in cash, cash equivalents and restricted cash	336,229	63,197	20,982
Cash, cash equivalents and restricted cash at beginning of year	201,260	138,063	117,081
Cash, cash equivalents and restricted cash at end of year	537,489	201,260	138,063
Supplemental disclosure of cash flow information:
Cash paid for income taxes	2,296	876	947
Non-cash investing and financing activities:
Increase (decrease) in purchases of property and equipment included in liabilities	(11,435)	6,334	763
Vesting of early exercised stock options	260	366	480
Unrealized short-term gain (loss) on marketable securities	$ 578	$ 791	$ (677)

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	12 Months Ended
	Jan. 31, 2020
Accounting Policies [Abstract]
Description of Business and Summary of Significant Accounting Policies	Description of Business and Summary of Significant Accounting Policies Business Slack Technologies, Inc. (the “Company” or “Slack”) operates a business technology software platform that brings together people, applications, and data and sells its offering under a software-as-a-service model. The Company was incorporated in Delaware in 2009 as Tiny Speck, Inc. In 2014, the Company changed its name to Slack Technologies, Inc. and publicly launched its current offering. The Company is headquartered in San Francisco, California. Fiscal Year The Company’s fiscal year ends on January 31. References to fiscal year 2020, for example, refer to the fiscal year ended January 31, 2020. Basis of Presentation and Consolidation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”), and include the accounts of the Company and its wholly owned and majority-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements include 100% of the accounts of wholly owned and majority-owned subsidiaries and the ownership interest of minority investors is recorded as noncontrolling interest. Direct Listing On June 20, 2019 , the Company completed a direct listing of its Class A common stock (the “Direct Listing”) on the New York Stock Exchange (“NYSE”). The Company incurred nonrecurring fees related to financial advisory service, audit, and legal expenses in connection with the Direct Listing and recorded $30.4 million in general and administrative expense for the year ended January 31, 2020 . Prior to the Direct Listing, all shares of outstanding convertible preferred stock were converted into an equivalent number of shares of Class B common stock. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the consolidated financial statements. On a regular basis, management evaluates these estimates and assumptions; however, actual results could materially differ from these estimates. The Company’s most significant estimates and judgments involve revenue recognition, stock-based compensation including the estimation of fair value of common stock, valuation of strategic investments, valuation of acquired goodwill and intangibles from acquisitions, period of benefit for deferred costs, and uncertain tax positions. Revenue Recognition The Company derives its revenue from monthly and annual subscription fees earned from customers accessing Slack. The Company’s policy is to exclude sales and other indirect taxes when measuring the transaction price of its subscription agreements. The Company accounts for revenue contracts with customers through the following steps: • Identification of the contract, or contracts, with the customer; • Identification of the performance obligations in the contract; • Determination of the transaction price; • Allocation of the transaction price to the performance obligations in the contract; and • Recognition of the revenue when, or as, the Company satisfies a performance obligation. Subscription revenue is recognized on a straight-line basis over the contractual term of the arrangement beginning on the date that the service is made available to the customer. The Company’s subscription service contracts are generally one month to thirty-six months in duration and are generally non-cancellable. Customers are billed either annually or monthly generally in advance of services. The contracts do not provide customers with the right to take possession of the software supporting Slack. The Company’s arrangements do not contain general rights of return. Amounts that have been invoiced are recorded in accounts receivable and in revenue or deferred revenue, depending on whether the performance obligation has been satisfied. For certain multi-year agreements, revenue recognition may occur in advance of invoicing, resulting in a contract asset when a conditional right to consideration exists and transfer of control for the services rendered. These contract assets are included in prepaid expenses and other current assets. The Company maintains a fair billing policy, under which certain customers maintain a credit balance if they have not used the entirety of the allotment of users for which they have paid during the contractual term of their respective arrangements. These credits, accounted for as a part of deferred revenue, may be carried over to offset billings related to increases in a customer’s number of active users and are not refundable for cash. A majority of the Company’s contracts give a right to bill for additional usage, and this is deemed variable consideration. The variable consideration is allocated to the distinct day the services are completed, as services provided to the additional users are specific to the period that the usage occurs. To the extent that the Company believes it is probable that a significant reversal would not occur, an estimate is made for the revenue associated with incremental usage during a period. The incremental revenue recognized associated with these estimates has not been material for any period presented. Cost of Revenue Cost of revenue consists primarily of expenses related to hosting Slack and providing ongoing customer experience support for paid customers, including employee compensation (including stock-based compensation) and other employee-related expenses for customer experience and technical operations staff, payments to outside service providers, third-party hosting costs, payment processing fees and amortization of internally-developed and purchased technology. Stock-Based Compensation The Company measures compensation for all stock-based payment awards, including stock options, restricted stock units (“RSUs”), restricted stock awards (“RSAs”), and purchase rights issued under the 2019 Employee Stock Purchase Plan (“ESPP”) granted to employees, directors, and nonemployees, based on the estimated fair value of the awards on the date of grant. The fair value of each stock option and purchase rights issued under the ESPP granted is estimated using the Black-Scholes option pricing model. Stock-based compensation is recognized on a straight-line basis over the requisite service period, except for the RSUs granted under the 2009 Stock Plan (the “2009 Plan”). Under the 2009 Plan, the Company granted RSUs to its employees and directors with both a service-based vesting condition and a performance-based vesting condition. The service-based vesting period for these awards was typically four years with a cliff vesting period of one year and continued vesting quarterly thereafter. The fair value of RSUs was estimated based on the fair market value of t he Company’s common stock at the date of grant. On June 20, 2019 , the performance vesting condition was satisfied upon the completion of the Direct Listing and as a result, the Company recorded cumulative stock-based compensation of $245.1 million related to all then-outstanding RSUs granted under the 2009 Plan. The Company recognizes stock compensation associated with the RSUs granted under the 2009 Plan using the accelerated attribution method over the requisite service period. The Company also granted stock options and RSAs to its employees and directors under the 2009 Plan with a service-based vesting condition. The service-based vesting period for these awards is typically four years with a cliff vesting period of one year and continued vesting monthly thereafter. The fair value of each stock option is estimated using the Black-Scholes option pricing model. The fair value of RSAs is estimated based on the fair market value of t he Company’s common stock at the date of grant. Under the 2019 Stock Option and Incentive Plan (the “2019 Plan”), the Company grants RSUs and stock options to its employees and directors with a service-based vesting condition. The service-based vesting period for these awards is typically four years with a cliff vesting period of one year and continued vesting quarterly thereafter. Research and Development Costs Research and development costs are expensed as incurred and consist primarily of personnel costs and allocated overhead. Advertising Costs Advertising costs are expensed as incurred and were $38.1 million , $61.7 million , and $35.5 million for the years ended January 31, 2020 , 2019 , and 2018 , respectively. Advertising costs are included in sales and marketing expense in the accompanying consolidated statements of operations. Income Taxes The Company recognizes deferred tax liabilities and assets for the expected future tax consequences of temporary differences between the carrying amounts and the tax bases of assets and liabilities. A valuation allowance is established, when necessary, to reduce deferred tax assets to the amount that is more likely than not to be realized. The Company accounts for uncertain tax positions based on an evaluation as to whether it is more likely than not that a tax position will be sustained on audit, including resolution of any related appeals or litigation processes. This evaluation is based on all available evidence and assumes that the appropriate tax authorities have full knowledge of all relevant information concerning the tax position. The tax benefit recognized is based on the largest amount that is greater than 50% likely of being realized upon ultimate settlement. The Company includes interest expense and penalties related to its uncertain tax positions in interest expense and other expense, respectively. Financial Information about Segments and Geographical Areas The Company has one business activity and there are no segment managers who are held accountable for operations, results of operations, or plans for levels or components below the consolidated unit level. The Company’s chief operating decision maker is its Chief Executive Officer, who reviews the financial information presented on a consolidated basis for purposes of allocating resources and evaluating the Company’s financial performance. Accordingly, the Company has determined that it operates in a single operating and reporting segment. See Note 2 and 15 for information regarding the Company’s revenue and long-lived assets by geographic area. Foreign Currency Translation The functional currency of the Company’s foreign subsidiaries is the U.S. dollar. Accordingly, each foreign subsidiary remeasures monetary assets and liabilities at period-end exchange rates, while nonmonetary items are remeasured at historical rates. Revenue and expense accounts are remeasured at the average exchange rate in effect during the year. Remeasurement adjustments are recognized in the accompanying consolidated statements of operations as transaction gains or losses in the year of occurrence as other income (expense). Cash and Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Cash equivalents consist of funds deposited into money market funds, and commercial paper. Restricted cash consists of cash deposited with financial institutions as collateral for the Company’s obligations under its facility leases. A reconciliation of cash, cash equivalents and restricted cash to the accompanying consolidated statements of cash flows is as follows (in thousands): As of January 31, 2020 2019 Cash and cash equivalents $ 498,999 $ 180,770 Restricted cash 38,490 20,490 Total cash, cash equivalents and restricted cash $ 537,489 $ 201,260 Marketable Securities The Company determines the appropriate classification of its investments in marketable securities at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its marketable securities as available-for-sale. All of the Company’s available-for-sale investments consist of debt securities, adjusted for amortization of premiums and discounts to maturity and such amortization is included in other income (expense), net. After consideration of the Company’s capital preservation objectives, as well as its liquidity requirements, the Company may sell securities prior to their stated maturities. As the Company views these securities as available to support current operations, it has classified all available-for-sale securities as short-term. The Company carries its available-for-sale securities at fair value and reports the unrealized gains and losses as a component of stockholders’ equity, except for unrealized losses determined to be other than temporary. The Company evaluates its investments periodically for possible other-than-temporary impairment. A decline in fair value below the amortized costs of debt securities is considered an other-than-temporary impairment if the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security before recovery of the entire amortized cost basis. In those instances, an impairment charge equal to the difference between the fair value and the amortized cost basis is recognized in earnings. Regardless of the Company’s intent or requirement to sell a debt security, impairment is considered other than temporary if the Company does not expect to recover the entire amortized cost basis. Strategic Investments In December 2015, the Company committed $13.0 million to a newly formed entity, Slack Fund L.L.C. (“Slack Fund”), in exchange for a 52% voting interest. Slack Fund is in the business of purchasing, selling, investing and trading in minority equity and convertible debt securities of privately-held companies that develop applications that have potential for substantial contribution to Slack and its ecosystem. Slack Fund has a duration of ten years and its duration may be extended for three additional years. At dissolution, Slack Fund will be liquidated and the remaining assets of the Slack Fund will be distributed to the investors based on their voting interest. As of January 31, 2020 , the Company had contributed its full commitment of $13.0 million . Additionally, the minority investors in Slack Fund are also investors in the Company. The Company has elected the measurement alternative, defined as cost, less any impairment, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. These investments are valued using significant unobservable inputs or data in inactive markets which require judgment due to the absence of market prices and inherent lack of liquidity. This could result in volatility in other income (expense), net on the accompanying consolidated statements of operations in future periods due to the valuation and timing of identical or similar investments of the same issuer. Concentration of Credit Risk Financial instruments that potentially subject the Company to credit risk primarily consist of cash and cash equivalents, restricted cash, marketable securities, and accounts receivable. For cash, cash equivalents, restricted cash, and marketable securities, the Company is exposed to credit risk in the event of default by the financial institutions to the extent of the amounts recorded on the accompanying consolidated balance sheets that are in excess of federal insurance limits. For accounts receivable, the Company is exposed to credit risk in the event of nonpayment by customers to the extent of the amounts recorded on the accompanying consolidated balance sheets. No customer accounted for 10% or greater of total accounts receivable as of January 31, 2020 and 2019 . There were no customers representing 10% or greater of revenue for the years ended January 31, 2020 , 2019 , and 2018 . Fair Value of Financial Instruments The Company records its financial assets and liabilities at fair value. The carrying amounts of the Company’s financial instruments, which include cash, cash equivalents, restricted cash, accounts receivable, and accounts payable, approximate their fair values due to their short-term nature. The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value, and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows: • Level 1 inputs: Unadjusted quoted prices in active markets for identical assets or liabilities accessible to the reporting entity at the measurement date. • Level 2 inputs: Other than quoted prices included in Level 1 inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the asset or liability. • Level 3 inputs: Unobservable inputs for the asset or liability used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at measurement date. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Accounts Receivable, Net Trade accounts receivable are recorded at invoiced amounts and do not bear interest. The Company generally does not require collateral and performs ongoing credit evaluations of its customers and provides for expected losses. The expectation of collectability is based on the Company’s review of credit profiles of customers, contractual terms and conditions, current economic trends, and historical payment experience. If events or changes in circumstances indicate that specific receivable balances may be impaired, further consideration is given to the collectability of those balances and an allowance is recorded accordingly. Past-due receivable balances are written off when internal collection efforts have been unsuccessful in collecting the amount due. The allowance for doubtful accounts reflects the Company’s best estimate of probable losses inherent in the receivables portfolio determined on the basis of historical experience, specific allowances for known troubled accounts and other currently available evidence. The Company has not experienced significant credit losses from accounts receivable. The allowance for doubtful accounts and the changes in the allowance for doubtful accounts were not material, for the years ended January 31, 2020 and 2019 . Property and Equipment, Net Property and equipment, net is stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful life of the related asset, which is typically two years for computer equipment and software, five years for furniture and fixtures, and in the case of leasehold improvements, the remaining term of the lease, unless the useful life of the asset is shorter. Maintenance and repairs are charged to expense as incurred. Internal-Use Software Development Costs The Company capitalizes qualifying internal-use software development costs that are incurred during the application development stage. Capitalization of costs begins when two criteria are met: (i) the preliminary project stage is completed and (ii) it is probable that the software will be completed and used for its intended function. Capitalization ceases when the software is substantially complete and ready for its intended use, including the completion of all significant testing. Costs related to preliminary project activities and post-implementation operating activities are expensed as incurred. Capitalized costs are included in property and equipment. These costs are amortized over the estimated useful life of the software (generally two years ) on a straight-line basis. Management evaluates the useful life of these assets on an annual basis and tests for impairment whenever events or changes in circumstances occur that could impact the recoverability of these assets. The amortization of costs related to the platform applications is included in cost of revenue. Business Combinations The Company applies the acquisition method of accounting for business combinations. Under this method of accounting, all assets acquired and liabilities assumed are recorded at their respective fair values at the date of the acquisition. Determining the fair value of assets acquired and liabilities assumed requires management’s judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, discount rates, intangibles, and other asset lives, among other items. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Market participants are assumed to be buyers and sellers in the principal (most advantageous) market for the asset or liability. Additionally, fair value measurements for an asset assume the highest and best use of that asset by market participants. As a result, the Company may be required to value the acquired assets at fair value measures that do not reflect its intended use of those assets. Use of different estimates and judgments could yield different results. Any excess of the purchase price over the fair value of the net assets acquired is recognized as goodwill. If the fair value of net assets acquired exceeds the fair value of purchase price, a gain on bargain purchase is recognized within the accompanying consolidated statements of operations. Although the Company believes the assumptions and estimates it has made are reasonable and appropriate, they are based in part on historical experience and information that may be obtained from the management of the acquired company and are inherently uncertain. During the measurement period, which may be up to one year from the acquisition date, the Company may record adjustments to the assets acquired and liabilities assumed with the corresponding offset to goodwill for facts and considerations that were known at the acquisition date. Upon the conclusion of the measurement period or final determination of the values of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded within the accompanying consolidated statements of operations. Accounting for Impairment of Long-Lived Assets The Company evaluates long-lived assets, such as property and equipment and acquired intangibles, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets held and used is measured by comparison of the carrying amount of an asset or an asset group to estimated undiscounted future net cash flows expected to be generated by the asset or asset group. If the carrying amount of an asset exceeds these estimated future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the assets exceeds the fair value of the asset or asset group, based on discounted cash flows. There were no material impairment charges recorded for the years ended January 31, 2020 , 2019 , and 2018 . Goodwill Goodwill is not amortized, but rather is tested for impairment at least annually or more frequently if indicators of impairment are present. The Company operates as one reporting unit and performs its annual goodwill impairment analysis as of the first day of the fourth quarter of each year. In assessing impairment on goodwill, the Company may bypass a qualitative assessment and proceeds directly to performing a quantitative evaluation of the fair value of its single reporting unit, in order to compare it against the carrying value of the reporting unit. A goodwill impairment charge is recognized for the amount by which the reporting unit’s fair value is less than its carrying value. Any loss recognized will not exceed the total amount of goodwill allocated to that reporting unit. Based on the results of the goodwill impairment analysis, the Company determined that no impairment charge needed to be recorded for any periods presented. Operating Leases The Company leases real estate facilities under non-cancelable operating leases with various expiration dates through fiscal year 2031. The Company determines if an arrangement contains a lease at inception based on whether there is an identified property, plant or equipment and whether the Company controls the use of the identified asset throughout the period of use. The Company adopted the Accounting Standard Update (“ASU”) No. 2016-02, Leases ( Topic 842 ) on November 1, 2019. Operating leases are included in operating lease right-of-use (“ROU”) assets and in operating lease liabilities in the accompanying consolidated balance sheets. Operating lease ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and lease liabilities are recognized at the lease inception date based on the present value of lease payments over the lease term discounted based on the more readily determinable of (i) the rate implicit in the lease or (ii) the Company’s incremental borrowing rate (which is the estimated rate the Company would be required to pay for a collateralized borrowing equal to the total lease payments over the term of the lease). Because the Company’s operating leases generally do not provide an implicit rate, the Company estimates its incremental borrowing rate based on the information available at lease commencement date for borrowings with a similar term. The Company’s operating lease ROU assets are measured based on the corresponding operating lease liability adjusted for (i) payments made to the lessor at or before the commencement date, (ii) initial direct costs incurred and (iii) tenant incentives under the lease. The Company does not assume renewals or early terminations unless it is reasonably certain to exercise these options at commencement. The Company does not allocate consideration between lease and non-lease components. Variable lease payments are recognized in the period in which the obligation for those payments are incurred. In addition, the Company does not recognize ROU assets or lease liabilities for leases with a term of 12 months or less of all asset classes. Operating lease expense is recognized on a straight-line basis over the lease term. Lease accounting prior to the adoption of Topic 842 For leases that contain rent escalation, rent concession provisions, or tenant improvement allowances, the Company recorded the total rent expense during the lease term on a straight-line basis over the term of the lease. The Company recorded the difference between the rent paid and the straight-line rent expense as a deferred rent liability within accrued expenses and other current liabilities and long-term liabilities. As of January 31, 2019, the Company recorded a deferred rent liability of $18.7 million of which $17.9 million were included in other liabilities in the accompanying consolidated balance sheets. Deferred Revenue Deferred revenue consists of customer billings in advance of revenue being recognized from the Company’s contracts, including credit balances due to the Company’s fair billing policy. Deferred revenue is generally recognized during the succeeding twelve‑month period. Deferred Contract Acquisition Costs, Net Sales commissions earned by the Company’s sales force are considered to be incremental and recoverable costs of obtaining a contract with a customer. As a result, these amounts have been capitalized as deferred contract acquisition costs within prepaid expenses and other current assets and other assets on the accompanying consolidated balance sheets. Deferred contract acquisition costs are typically amortized over a period of benefit of four years . The period of benefit is estimated by considering factors such as historical customer attrition rates, the useful life of the Company’s technology, and the impact of competition in its industry as well as other factors. Amortized costs are included in sales and marketing expense in the accompanying consolidated statements of operations. Recently Adopted Accounting Standards In February 2016, the Financial Accounting Standards Board (“FASB”) issued Topic 842, Leases , which generally requires companies to recognize operating and financing lease liabilities and corresponding ROU assets on the balance sheet. The Company early adopted the standard as of November 1, 2019, using the modified retrospective approach and has elected to use the optional transition method which allows the Company to apply the guidance of ASC 840, including disclosure requirements, in the comparative periods presented. The Company does not believe reflecting the adoption as of February 1, 2019 would have materially impacted its consolidated balance sheet as of January 31, 2020 or its results of operations or operating cash flows for the year then ended. In addition, the Company elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed the Company to carry forward the historical lease classification related to agreements entered prior to adoption. The adoption of the new standard resulted in recognition of operating lease ROU assets and operating lease liabilities of $198.4 million and $228.4 million , respectively, as of November 1, 2019. There was no cumulative impact of transition to retained earnings as of the adoption date. The standard did not materially impact the accompanying consolidated statements of operations and had no impact on the accompanying consolidated statements of cash flows. In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (Subtopic 825-10) and issued a subsequent amendment to the initial guidance within ASU 2018-03, which requires entities to carry all investments in equity securities at fair value and recognize any changes in fair value in net income. Under the standard, equity investments that do not have readily determinable fair values and do not qualify for the net asset value practical expedient are eligible for the measurement alternative. For our equity investments in private companies, we will elect the measurement alternative, defined as cost, less any impairment, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. The guidance was effective for the Company’s fiscal year beginning February 1, 2018 on a prospective basis for the amendments related to equity securities without readily determinable fair values existing as of the date of adoption. The Company adopted the new standard as of February 1, 2018 and it did not have a material impact on its consolidated financial statements. The impact of the new standard going forward could result in volatility in other income (expense), net on the accompanying consolidated statements of operations in future periods due to the valuation and timing of identical or similar investments of the same issuer. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740) Intra-Entity Transfers of Assets other than Inventory, which amends the guidance used in the recognition of current and deferred income taxes for an intra-entity transfer of assets other than inventory. The guidance requires an entity recognize the income tax consequences of an intra-entity transfer of an asset other than inventory at the time of transfer. The guidance is effective for annual and interim reporting periods beginning after December 15, 2017 for public entities. The Company adopted ASU No. 2016-06 as of February 1, 2018. The adoption of this guidance did not have a material impact on the acco

Revenue

Revenue	12 Months Ended
	Jan. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Contract Balances Contract liabilities consist of deferred revenue. The changes in deferred revenue were as follows (in thousands): Year Ended January 31, 2020 Balance, beginning of period $ 241,873 Billings 765,263 Revenue (630,422 ) Balance, end of period $ 376,714 Approximately 36% of revenue recognized in the year ended January 31, 2020 was from the deferred revenue balance as of January 31, 2019 . Remaining Performance Obligations The Company applies the practical expedient in paragraph 606-10-50-14 and does not disclose information about remaining performance obligations that have original expected durations of one year or less, which applies primarily to its monthly and annual subscription contracts. As of January 31, 2020 , the remaining performance obligations that were unsatisfied or partially unsatisfied at the end of the reporting period was $328.1 million , of which 57% is expected to be recognized in the twelve months following January 31, 2020, with the balance to be recognized as revenue thereafter. Disaggregation of Revenue The following table shows the Company’s revenue by geographic areas, as determined based on the billing address of its customers (in thousands): Year ended January 31, 2020 2019 2018 United States $ 394,716 $ 255,155 $ 144,720 International 235,706 145,397 75,824 Total $ 630,422 $ 400,552 $ 220,544 No individual foreign country contributed in excess of 10% of revenue for the years ended January 31, 2020 , 2019 , and 2018 . Deferred Contract Acquisition Costs, Net The Company deferred incremental costs of obtaining a contract of $23.6 million , $15.8 million , and $4.7 million during the years ended January 31, 2020 , 2019 , and 2018 , respectively. Deferred contract acquisition costs, net included in prepaid expenses and other current assets were $11.2 million and $5.3 million as of January 31, 2020 and 2019 , respectively. Deferred contract acquisition costs, net included in other assets were $21.4 million and $11.9 million as of January 31, 2020 and 2019 , respectively. Amortized deferred contract acquisition costs were $8.2 million , $3.2 million , and $0.6 million for the years ended January 31, 2020 , 2019 , and 2018 , respectively. There was no impairment loss in relation to the deferred contract acquisition costs for any period presented in the accompanying consolidated statements of operations.

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	12 Months Ended
	Jan. 31, 2020
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents, and Marketable Securities	Cash, Cash Equivalents and Marketable Securities The carrying amounts and estimated fair value of cash, cash equivalents, and marketable securities consisted of the following (in thousands): As of January 31, 2020 2019 Cash and cash equivalents: Cash $ 71,593 $ 62,033 Money market funds 357,524 118,737 Commercial paper 69,882 — Cash and cash equivalents $ 498,999 $ 180,770 Marketable securities: Commercial paper $ 19,795 $ 17,462 U.S. agency securities 29,515 44,879 U.S. government securities 97,172 370,574 International government securities 8,115 36,734 Corporate bonds 114,996 190,652 Total marketable securities $ 269,593 $ 660,301 The following tables summarize unrealized gains and losses related to cash equivalents and marketable securities on the Company’s consolidated balance sheets (in thousands): As of January 31, 2020 Amortized Unrealized Unrealized Fair value Cash and cash equivalents: Cash $ 71,593 $ — $ — $ 71,593 Money market funds 357,524 — — 357,524 Commercial paper 69,891 — (9 ) 69,882 Total cash and cash equivalents 499,008 — (9 ) 498,999 Marketable securities: Commercial paper 19,799 4 (8 ) 19,795 U.S. agency securities 29,460 55 — 29,515 U.S. government securities 97,071 102 (1 ) 97,172 International government securities 8,109 6 — 8,115 Corporate bonds 114,871 139 (14 ) 114,996 Total marketable securities 269,310 306 (23 ) 269,593 Total cash, cash equivalents and marketable securities $ 768,318 $ 306 $ (32 ) $ 768,592 As of January 31, 2019 Amortized Unrealized Unrealized Fair value Cash and cash equivalents: Cash $ 62,033 $ — $ — $ 62,033 Money market funds 118,737 — — 118,737 Total cash and cash equivalents 180,770 — — 180,770 Marketable securities: Commercial paper 17,461 1 — 17,462 U.S. agency securities 44,886 7 (14 ) 44,879 U.S. government securities 370,498 143 (67 ) 370,574 International government securities 36,810 — (76 ) 36,734 Corporate bonds 190,944 — (292 ) 190,652 Total marketable securities 660,599 151 (449 ) 660,301 Total cash, cash equivalents and marketable securities $ 841,369 $ 151 $ (449 ) $ 841,071 The Company periodically evaluates its investments for other-than-temporary declines in fair value. The unrealized losses on the available-for-sale securities were primarily due to unfavorable changes in interest rates subsequent to the initial purchase of these securities. Gross unrealized losses of the Company’s available-for-sale securities that have been in a continuous unrealized loss position for twelve months or longer was immaterial as of January 31, 2020 and 2019 . The Company expects to recover the full carrying value of its available-for-sale securities in an unrealized loss position as it does not intend or anticipate a need to sell these securities prior to recovering the associated unrealized losses. As a result, the Company does not consider any portion of the unrealized losses as of January 31, 2020 or 2019 to represent an other-than temporary impairment or credit losses. The following table classifies marketable securities by contractual maturities (in thousands): As of January 31, 2020 2019 Due in one year $ 190,344 $ 506,297 Due in one to two years 79,249 154,004 Total $ 269,593 $ 660,301

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Jan. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company’s money market funds and sweep account are classified within Level 1 of the fair value hierarchy because they are valued using quoted prices in active markets. The Company’s commercial paper, U.S. agency and government securities, international government securities, and corporate bonds are classified within Level 2 of the fair value hierarchy because they have been valued using inputs other than quoted prices in active markets that are observable directly or indirectly. The Company’s strategic investments in privately held companies are classified within Level 3 of the fair value hierarchy because they have been valued using unobservable inputs for which the Company has been required to develop its own assumptions. Realized and unrealized gains and losses relating to the strategic investments are recorded in other income (expense), net in the accompanying consolidated statements of operations. The following table provides the financial instruments measured at fair value on a recurring basis, within the fair value hierarchy (in thousands): As of January 31, 2020 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 357,524 $ — $ — $ 357,524 Commercial paper — 69,882 — 69,882 Total cash equivalents $ 357,524 $ 69,882 $ — $ 427,406 Marketable securities: Commercial paper $ — $ 19,795 $ — $ 19,795 U.S. agency securities — 29,515 — 29,515 U.S. government securities — 97,172 — 97,172 International government securities — 8,115 — 8,115 Corporate bonds — 114,996 — 114,996 Total marketable securities $ — $ 269,593 $ — $ 269,593 Noncurrent assets: Strategic investments $ — $ — $ 28,814 $ 28,814 As of January 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 118,737 $ — $ — $ 118,737 Total cash equivalents $ 118,737 $ — $ — $ 118,737 Marketable securities: Commercial paper $ — $ 17,462 $ — $ 17,462 U.S. agency securities — 44,879 — 44,879 U.S. government securities — 370,574 — 370,574 International government securities — 36,734 — 36,734 Corporate bonds — 190,652 — 190,652 Total marketable securities $ — $ 660,301 $ — $ 660,301 Noncurrent assets: Strategic investments $ — $ — $ 12,334 $ 12,334 The following table presents additional information about Level 3 assets measured at fair value on a recurring basis (in thousands): Year ended January 31, 2020 2019 Balance at beginning of period $ 12,334 $ 7,623 Purchases 14,132 2,276 Proceeds from liquidation (3,251 ) (1,266 ) Realized gains (losses) 2,285 (131 ) Unrealized gains relating to investments still held at reporting date 3,314 3,832 Balance at end of period $ 28,814 $ 12,334

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Jan. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net The following is a summary of the Company’s property and equipment by category (in thousands): As of January 31, 2020 2019 Computer equipment and software $ 3,183 $ 2,222 Furniture and fixtures 27,384 19,693 Capitalized internal-use software costs 4,241 4,241 Leasehold improvements 98,770 86,258 Construction in progress 10,345 6,076 Property and equipment, gross 143,923 118,490 Less: accumulated depreciation and amortization (41,583 ) (30,131 ) Property and equipment, net $ 102,340 $ 88,359 Depreciation and amortization expense was $23.0 million , $15.0 million , and $13.8 million for the years ended January 31, 2020 , 2019 , and 2018 , respectively. The Company capitalized internal-use software costs of $0 , $0.8 million , and $50,000 for the years ended January 31, 2020 , 2019 , and 2018 , respectively. Amortization expense of capitalized internal-use software costs totaled $0.5 million , $0.3 million , and $1.2 million for the years ended January 31, 2020 , 2019 , and 2018 , respectively. The net carrying value of capitalized internal-use software at January 31, 2020 and 2019 was $0.4 million and $0.9 million , respectively.

Operating Leases

Operating Leases	12 Months Ended
	Jan. 31, 2020
Leases [Abstract]
Operating Leases	Operating Leases The Company leases real estate facilities under non-cancelable operating leases with various expiration dates through fiscal year 2031. The Company adopted Topic 842 as of November 1, 2019, using the modified retrospective approach. Rent expense, net of sublease income under ASC 840 was $26.3 million for the nine months ended October 31, 2019, and $27.7 million and $17.5 million for the years ended January 31, 2019 and 2018, respectively. In the fourth quarter of fiscal year 2020, the Company recorded operating lease costs of $11.7 million including variable operating lease costs of $1.7 million and short-term leases of $0.7 million . The following table sets forth a summary of and other information pertaining to the Company’s operating leases for the fourth quarter of fiscal year 2020 (dollars in thousands): Operating cash flows used for operating leases $ 9,495 Operating lease liabilities arising from obtaining ROU assets $ 4,832 Weighted average remaining terms 8.3 years Weighted average discount rate 5.2 % Future minimum lease payments under non-cancelable operating leases with initial lease terms in excess of one year as of January 31, 2020 as follows (in thousands): Year ending January 31, 2021 $ 37,633 2022 50,472 2023 51,276 2024 49,723 2025 52,373 Thereafter 254,256 Gross lease payments 495,733 Less: Imputed interest (64,683 ) Less: Tenant improvement receivables (14,381 ) Less: Leases executed but not yet commenced (189,826 ) Present value of lease liabilities $ 226,843 As of January 31, 2020 , the Company had commitments of $189.8 million for non-cancelable operating leases of real estate facilities that have not yet commenced, and therefore are not included in the ROU assets or operating lease liabilities. These operating leases will commence in fiscal year 2021 with lease terms of 10.3 years to 12.0 years .

Acquisitions

Acquisitions	12 Months Ended
	Jan. 31, 2020
Business Combinations [Abstract]
Acquisitions	Acquisitions Astro Technology In September 2018, the Company completed its acquisition of all issued and outstanding shares of Astro Technology Inc. (“Astro”), a pre-revenue start-up company that provides artificial-intelligence (AI) enhanced communications solutions, for a total purchase price of $43.3 million in cash. The Company has accounted for this acquisition as a business combination and has completed the valuation of the assets acquired and liabilities assumed and the allocation of the purchase price to goodwill as of January 31, 2019. A summary of the allocation of the purchase price is presented as follows (in thousands): Identified intangible asset - developed technology $ 5,300 Goodwill 37,795 Net tangible assets acquired 234 Total purchase price $ 43,329 The goodwill was primarily attributed to the value of synergies created with the Company’s current and future offerings and the value of the assembled workforce. The Company anticipates both goodwill and intangible assets to be fully deductible for income tax purposes. The Company also agreed to pay additional cash consideration of $10.7 million for unvested securities in return for future services to be provided by certain employees acquired from Astro upon continued employment by the Company. The cash consideration will be paid on each original vesting date of the unvested securities through June 2022. The Company accounted for the cash consideration outside the business combination and recorded compensation expense of $3.7 million and $1.6 million in research and development expense in the accompanying consolidated statements of operations for the year ended January 31, 2020 and 2019 , respectively. The Company incurred other acquisition related expenses of $0.4 million which were recorded in general and administrative expense in the accompanying consolidated statement of operations for the year ended January 31, 2019. Other Acquisitions During the year ended January 31, 2019, the Company completed other acquisitions and purchases of intangible assets for total consideration of $14.5 million , of which the remaining $5.3 million will be paid in the year ending January 31, 2021. In aggregate, $11.7 million was attributed to intangible assets, $2.2 million was attributed to goodwill, and $0.6 million was attributed to a service agreement. As part of one of the acquisitions referenced above, the Company concurrently entered into a two-year services agreement, a purchase of technology and a sale of its Class A common stock. Concurrent with this transaction, the Company sold 896,057 shares of Class A common stock to the sellers for $10.0 million . This represented a premium of $3.9 million over the then fair value of the shares which the Company recorded as a reduction to the acquisition price. These arrangements were treated as one transaction as they were executed at the same time and in contemplation of one another. The Company accounted for the transaction as an asset acquisition with $9.9 million being allocated to intangible assets and $0.6 million to the services arrangement. These acquisitions generally enhance the breadth and depth of the Company’s product offerings, expand its expertise in engineering, and are for defensive purposes to eliminate competition. The Company anticipates both goodwill and intangible assets from other acquisitions to be fully deductible for income tax purposes. Following are the details of all intangible assets acquired as a result of acquisitions for the year ended January 31, 2019 (dollars in thousands): Amount Weighted Customer relationships $ 9,100 7 years Developed technology 6,700 3 years Assembled workforce 1,198 2 years Fair value of intangible assets acquired $ 16,998 5 years

Goodwill and Intangible Assets,

Goodwill and Intangible Assets, Net	12 Months Ended
	Jan. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets, Net	Goodwill and Intangible Assets, Net Goodwill The following table reflects the changes in the carrying amount of goodwill (in thousands): Year ended January 31, 2020 2019 Balance at beginning of year $ 48,598 $ 8,653 Additions due to acquisitions — 39,945 Balance at end of year $ 48,598 $ 48,598 Intangible Assets, Net Intangible assets as of January 31, 2020 and 2019 consist of the following (in thousands, except years): As of January 31, 2020 Weighted-average Gross carrying Accumulated Net carrying Customer relationships 5.5 years $ 9,100 $ 2,004 $ 7,096 Developed technology 1.6 years 8,527 4,976 3,551 Patents 4.9 years 2,500 42 2,458 Assembled workforce 0.7 years 1,198 773 425 Total $ 21,325 $ 7,795 $ 13,530 As of January 31, 2019 Weighted-average remaining amortization period Gross carrying amount Accumulated amortization Net carrying amount Customer relationships 6.5 years $ 9,100 $ 704 $ 8,396 Developed technology 2.6 years 8,527 2,743 5,784 Assembled workforce 1.7 years 1,198 175 1,023 Total $ 18,825 $ 3,622 $ 15,203 The Company records amortization expense associated with customer relationships, developed technology, assembled workforce and patents in sales and marketing expense, cost of revenue, research and development expense and general and administrative expense, respectively, in the accompanying consolidated statements of operations. Amortization expense of intangible assets was $4.2 million , $1.8 million , and $0.5 million for the years ended January 31, 2020 , 2019 , and 2018 , respectively. As of January 31, 2020 , expected amortization expense relating to intangible assets for each of the next five years and thereafter is as follows (in thousands): Year ending January 31, 2021 $ 4,458 2022 3,118 2023 1,800 2024 1,800 2025 1,758 Thereafter 596 Total $ 13,530

Revolving Credit Facility

Revolving Credit Facility	12 Months Ended
	Jan. 31, 2020
Debt Disclosure [Abstract]
Revolving Credit Facility	Revolving Credit Facility On May 30, 2019 , the Company entered into a $215.0 million revolving credit and guaranty agreement with a syndicate of financial institutions. The revolving credit facility has an accordion option, which, if exercised, would allow the Company to increase the aggregate commitments by up to the greater of $200.0 million and 100% of the consolidated adjusted EBITDA of the Company and its subsidiaries, plus an unlimited amount subject to satisfaction of certain leverage ratio based compliance tests after giving effect to the exercise, in each case subject to obtaining additional lender commitments and satisfying certain conditions. Pursuant to the terms of the revolving credit facility, the Company may issue letters of credit under the revolving credit facility, which reduce the total amount available for borrowing under such facility. The revolving credit facility terminates on May 30, 2024 . Interest on borrowings under the revolving credit facility accrues at a variable rate tied to the prime rate or the LIBOR, plus the applicable margin, at the Company’s election. The margin is 0.25% in the case of prime rate loans and 1.25% in the case of LIBOR loans. Interest is payable quarterly in arrears. Pursuant to the terms of the revolving credit facility, the Company is required to pay an annual commitment fee that accrues at a rate of 0.10% per annum on the unused portion of the borrowing commitments under the revolving credit facility. In addition, the Company is required to pay a fee in connection with letters of credit issued and outstanding under the revolving credit facility that accrues at a rate of 1.25% per annum on the amount to be drawn under such letters of credit outstanding. There is an additional fronting fee of 0.125% per annum multiplied by the aggregate face amount of issued and outstanding letters of credit. The revolving credit facility contains customary conditions to borrowing, events of default, and covenants, including covenants that restrict the Company’s and its subsidiaries’ ability to, among other things, incur additional indebtedness, create or incur liens, merge or consolidate with other companies, sell substantially all of the Company’s assets, liquidate or dissolve, make distributions to the Company’s equity holders or its subsidiaries’ equity interests, pay dividends, make redemptions and repurchases of stock, or engage in transactions with affiliates. In addition, the revolving credit facility contains financial covenants, including a minimum liquidity balance and a minimum revenue amount. The Company has been in compliance with all covenants under the revolving credit facility since it entered into the revolving credit and guaranty agreement on May 30, 2019 . As of January 31, 2020 , the Company had no amounts or letters of credit issued and outstanding under the revolving credit facility. The Company’s total available borrowing capacity under the revolving credit facility was $215.0 million as of January 31, 2020 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Jan. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Letters of Credit As of January 31, 2020 , the Company had $38.5 million in standby letters of credit outstanding related to facility lease obligations in San Francisco, California and Denver, Colorado, which is included in restricted cash in the accompanying consolidated balance sheets. Hosting Commitments In April 2018, the Company executed an amendment to its existing agreement with Amazon Web Services (“AWS”). The amended agreement was effective as of May 1, 2018 and continues through July 31, 2023. The Company has minimum annual commitments of $50.0 million each year of the agreement term for a total minimum commitment of $250.0 million . As of January 31, 2020 , the Company had a remaining minimum payment obligation of $162.5 million to AWS through July 31, 2023. Legal Matters The Company records a loss contingency when it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. The Company also discloses material contingencies when it believes a loss is not probable but reasonably possible. Accounting for contingencies requires the Company to use judgment related to both the likelihood of a loss and the estimate of the amount or range of loss. The outcomes of the Company’s legal proceedings are inherently unpredictable and subject to significant uncertainties. For some matters for which a material loss is reasonably possible, an estimate of the amount of loss or range of losses is not possible, nor is the Company able to estimate the loss or range of losses that could potentially result from the application of non-monetary remedies. Many legal and tax contingencies can take years to be resolved. Until the final resolution of legal matters, all amounts of loss or range of losses are estimates only. The final losses the Company incurs may differ materially from these estimates. Beginning in September 2019, seven purported class action lawsuits were filed against the Company, its directors, certain of its officers, and certain investment funds associated with certain of its directors, each alleging violations of securities laws in connection with the Company’s registration statement on Form S-1 filed with the SEC. The Company believes these lawsuits are without merit and intends to vigorously defend them. Based on the preliminary nature of the proceedings in these cases, the outcome of these matters remains uncertain. In addition, the Company is involved from time to time in various claims and legal actions arising in the ordinary course of business. While it is not feasible to predict or determine the ultimate outcome of these matters, the Company believes that none of these ordinary course legal proceedings will have a material adverse effect on its consolidated financial statements. Indemnification Agreements In the ordinary course of business, the Company provides indemnifications of varying scope and terms to customers, business partners, vendors, lessors, investors, directors, officers, employees, and other parties with respect to certain matters. Indemnification may include losses from the Company’s breach of such agreements, intellectual property infringement claims made by third parties, and other liabilities relating to or arising from Slack, or the Company’s acts or omissions. These indemnifications may survive termination of the underlying agreement and the maximum potential amount of future indemnification payments may not be subject to a cap. It is not possible to determine the maximum potential loss under these indemnifications due to the Company’s limited history of prior indemnification claims and the unique facts and circumstances involved in each particular indemnification. The Company has not incurred material costs to defend lawsuits or settle claims related to these indemnifications as of January 31, 2020 . As of January 31, 2020 and 2019 , no material amounts were accrued.

Stockholders Equity

Stockholders Equity	12 Months Ended
	Jan. 31, 2020
Equity [Abstract]
Stockholders Equity	Stockholders’ Equity Convertible Preferred Stock Prior to the completion of the Direct Listing, all of the 373.4 million shares of convertible preferred stock converted into an equivalent number of shares of Class B common stock. At January 31, 2019, convertible preferred stock consisted of the following (in thousands): Shares Net Liquidation preference Authorized Outstanding Series A 84,751 84,751 $ 8,011 $ 8,060 Series B 43,320 43,320 10,674 10,700 Series C 64,805 64,805 42,678 42,750 Series D 47,059 42,490 108,266 108,350 Series D-1 1,235 1,235 2,561 3,149 Series E 26,787 22,602 134,832 135,000 Series E-1 6,047 6,047 37,940 37,950 Series F 19,867 19,867 154,957 155,000 Series F-1 6,793 6,793 52,940 53,000 Series G 24,718 24,718 229,648 230,000 Series G-1 2,149 2,149 20,000 20,000 Series G-2 17,241 17,241 150,000 150,000 Series G-3 1,465 1,465 12,714 8,700 Series H 35,150 33,470 398,082 398,468 Series H-1 9,202 2,419 28,798 28,798 Total 390,589 373,372 $ 1,392,101 $ 1,389,925 Preferred Stock The Company’s board of directors has the authority, without further action by the Company’s stockholders, to issue up to 100,000,000 shares of undesignated preferred stock with rights and preferences, including voting rights, designated from time to time by the board of directors. Common Stock On June 7, 2019, the Company amended and restated its certificate of incorporation to authorize 5,000,000,000 shares of Class A common stock and 700,000,000 shares of Class B common stock. Holders of Class A common stock and Class B common stock are entitled to dividends on a pro rata basis, when, as, and if declared by the Company’s board of directors, subject to preferences that may apply to any shares of preferred stock outstanding at the time. Holders of Class A common stock are entitled to one vote per share, and holders of Class B common stock are entitled to ten votes per share. Upon a liquidation, dissolution or winding-up of the Company, any distribution of proceeds to common stockholders will be made on a pro rata basis to the holders of Class A common stock, Class B common stock and any participating preferred stock outstanding at that time, subject to prior satisfaction of all outstanding debt and liabilities and the preferential rights of and the payment of liquidation preferences, if any, on any outstanding shares of preferred stock. Shares of Class B common stock will automatically convert into shares of Class A common stock upon a sale or transfer (other than with respect to certain estate planning and other transfers). All shares of Class B common stock outstanding in June 2029 will automatically convert into shares of Class A common stock. Class A common stock and Class B common stock is not redeemable at the option of the holder. The Company had reserved shares of common stock for future issuance as follows (in thousands): As of January 31, 2020 Stock options outstanding 8,425 Restricted stock units outstanding 42,002 Shares available for future grants 59,200 Shares available for ESPP 8,664 Total 118,291 Equity Incentive Plan The Company maintains two equity incentive plans: the 2009 Plan and the 2019 Plan. Upon the completion of the Direct Listing, the Company adopted the 2019 Plan and terminated the 2009 Plan with all shares that remained available for future issuance at the time canceled. The 2019 Plan is a successor to and continuation of the 2009 Plan that provides for the grant of stock options, stock appreciation rights, restricted stock awards, restricted stock units, and other forms of awards. The Company initially reserved 60.2 million shares of Class A common stock for the issuance of awards under the 2019 Plan. These available shares automatically increase each February 1, beginning on February 1, 2020, by 5% of the number of shares of the Company’s Class A and Class B common stock outstanding on the immediately preceding January 31, or such lesser number of shares as determined by the Company’s board of directors or compensation committee. Stock Options A summary of stock option activity under the 2009 Plan and 2019 Plan and related information is as follows (in thousands, except years and per share data): Number of stock options outstanding Weighted-average exercise price per share Weighted-average remaining contractual term (In years) Aggregate intrinsic value Outstanding at January 31, 2019 18,406 $ 0.94 6.12 $ 177,012 Granted 3,663 10.58 Exercised (13,268 ) 1.04 Canceled (376 ) 7.67 Outstanding at January 31, 2020 8,425 $ 4.68 6.27 $ 135,224 Stock options vested and exercisable at January 31, 2020 5,342 $ 1.44 4.96 $ 103,049 Stock options vested and expected to vest at January 31, 2020 8,425 $ 4.68 6.27 $ 135,224 The total grant-date fair value of stock options granted in the years ended January 31, 2020 , 2019 , and 2018 was $21.4 million , $0 , and $0.1 million , respectively. The total intrinsic value of stock options exercised in the years ended January 31, 2020 , 2019 , and 2018 , was $393.3 million , $30.0 million , and $13.6 million , respectively. As of January 31, 2020 , there was $16.7 million of total unrecognized stock-based compensation related to outstanding stock options, which will be recognized on a straight-line basis over a weighted average period of 4.8 years . RSUs and RSAs The fair value of RSUs and RSAs are determined using the fair value of the Company’s common stock on the date of grant. A summary of RSUs and RSAs activity under the 2009 Plan and 2019 Plan is as follows (in thousands, except per share data): Restricted stock units Restricted stock awards Number of shares Weighted-average grant date fair value (per share) Number of shares Weighted-average grant date fair value (per share) Unvested at January 31, 2019 63,114 $ 4.87 2,289 $ 7.23 Granted 23,804 18.93 505 13.60 Released (40,318 ) 4.84 (1,205 ) 7.74 Canceled (4,598 ) 8.45 (10 ) 2.37 Unvested at January 31, 2020 42,002 $ 12.48 1,579 $ 8.91 The weighted-average estimated fair value of RSUs granted in the year ended January 31, 2019 and 2018 was $7.02 and $4.15 per share, respectively. The weighted-average estimated fair value of RSAs granted in the year ended January 31, 2019 was $7.86 per share. No RSAs were granted in the year ended January 31, 2018. As of January 31, 2020 , the Company had $313.6 million of unrecognized stock-based compensation related to RSUs, which will be recognized over the weighted average remaining requisite service period of 1.5 years . As of January 31, 2020 , the Company had $13.5 million of unrecognized stock-based compensation related to RSAs, which will be recognized over the weighted average remaining requisite service period of 3.7 years . 2019 Employee Stock Purchase Plan The Company’s 2019 ESPP became effective on June 6, 2019. A total of 9.0 million shares of the Company’s Class A common stock were reserved for issuance under the 2019 ESPP. These available shares automatically increase each February 1, beginning on February 1, 2020, by the lesser of 6.0 million shares of the Class A common stock, 1% of the number of shares of the Company’s Class A and Class B common stock issued and outstanding on the immediately preceding January 31, or such lesser number of shares as determined by the Company’s compensation committee. The 2019 ESPP allows eligible employees to purchase shares of the Company’s Class A common stock at a discount of 15% through payroll deductions of their eligible compensation, subject to any plan limitations. Except for the first offering period from the date of the Direct Listing, the 2019 ESPP provides for separate six-month offering periods beginning each October 10 and April 10. On each purchase date, eligible employees will purchase the Company’s Class A common stock at a price per share equal to 85% of the lesser of (i) the fair market value of the Company’s Class A common stock on the offering date or (ii) the fair market value of the Company’s Class A common stock on the purchase date. For the year ended January 31, 2020 , 0.3 million shares of Class A common stock were issued under the 2019 ESPP. The Company selected the Black-Scholes option-pricing model as the method for determining the estimated fair value for the Company’s 2019 ESPP. As of January 31, 2020 , total unrecognized compensation cost related to the 2019 ESPP was $1.7 million which will be amortized over a weighted average period of 0.2 years . Tender Offers and Repurchases In connection with the Series G and G-1 convertible preferred stock financing, the Company facilitated a tender offer for all vested and outstanding shares of Class B common stock and all outstanding series of convertible preferred stock. In November 2017, the Company facilitated the sale of an aggregate of 17.9 million shares of vested and outstanding Class B common stock, Series A convertible preferred stock, Series D convertible preferred stock, Series D-1 convertible preferred stock and Series E convertible preferred stock from its existing or former employees and investors at a per share price of $8.37 , representing a 10% discount to the Series G and G-1 issuance price, for a total gross sale of $150.0 million . Following the close of the November 2017 tender offer, the Company repurchased an additional 0.8 million shares of Class B common stock from one of the Company’s co-founders at the same price per share of $8.37 for a total gross sale of $6.6 million . At the time of the tender offers, the fair value of the Company’s Class B common stock was $4.24 per share. For shares of Class B common stock repurchased from both current and former employees, the Company recorded compensation expense of $38.9 million related to the excess of the selling price per share of Class B common stock over the fair value of the tendered shares. In addition, the Company recorded deemed dividends of $40.9 million as a reduction to stockholder’s deficit in relation to the selling price per share of Class B common stock and convertible preferred stock paid to existing investors in excess of the original issuance price paid by investors of the shares tendered. Upon close of the tender offer, the Company retired the repurchased shares and subsequently issued the same number of shares in Series G-2 convertible preferred stock and Series G-3 convertible preferred stock to the lead investor of the Series G convertible preferred stock financing. In April and June 2017, the Company repurchased 0.1 million shares of common stock from former employees at a purchase price of $7.41 per share. In December 2017, the Company repurchased a combined 0.1 million shares of Class B common stock from one current and one former employee at a purchase price of $8.37 per share. For all the repurchased shares of common stock, the purchase price per share represented an excess to the fair value of the Company’s fair value of common stock at the time of each transaction. In total, the Company recorded $0.5 million of compensation expense and retired all repurchased shares of common stock as of January 31, 2018. A summary of the stock-based compensation related to the tender offers and repurchases, recorded in the accompanying consolidated statements of operations is as follows (in thousands): Year ended January 31, 2020 2019 2018 Cost of revenue $ — $ — $ 252 Research and development — — 30,674 Sales and marketing — — 6,549 General and administrative — — 1,899 Total $ — $ — $ 39,374 Stock Transfers During the years ended January 31, 2019 and 2020, certain of the Company’s existing investors, or investors to whom the Company waived its right of first refusal and transfer restrictions with respect to proposed transfers of outstanding common stock, acquired outstanding common stock from current or former employees of the Company for a purchase price greater than the fair value at the time of the transactions. In connection with these stock transfers, the Company waived its right of first refusal and other transfer restrictions applicable to such shares. As a result, the Company recorded stock-based compensation for the difference between the price paid and the fair value on the date of the transaction. A summary of the stock-based compensation related to the stock transfers recorded in the accompanying consolidated statements of operations is as follows (in thousands): Year ended January 31, 2020 2019 2018 Cost of revenue $ — $ 533 $ — Research and development — 6,228 — Sales and marketing — 1,707 — General and administrative — 6,353 — Total $ — $ 14,821 $ — Stock-Based Compensation A summary of the stock-based compensation excluding tender offers and stock transfers recorded in the accompanying consolidated statements of operations is as follows (in thousands): Year ended January 31, 2020 2019 2018 Cost of revenue $ 16,013 $ 199 $ 239 Research and development 226,507 3,720 4,586 Sales and marketing 98,797 970 1,495 General and administrative 85,207 3,422 2,389 Total $ 426,524 $ 8,311 $ 8,709 The fair value of stock options granted to employees is estimated on the date of grant using the Black-Scholes option valuation model. This stock-based compensation expense valuation model requires the Company to make assumptions and judgments regarding the variables used in the calculation. These variables include the expected term (weighted average period of time that the stock options granted are expected to be outstanding), the expected volatility of the Company’s common stock, expected risk-free interest rate and expected dividends. To the extent actual results differ from the estimates, the difference is recorded as a cumulative adjustment in the period estimates are revised. The Company accounts for forfeitures as they occur. The Company uses the simplified calculation of expected term, as the Company does not have sufficient historical data to use any other method to estimate expected term. Expected volatility is based on an average of the historical volatilities of the common stock of several entities with characteristics similar to those of the Company. The expected risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the option. The expected dividend yield is 0% as the Company has not paid, and does not expect to pay, cash dividends. The following assumptions used in the valuation of stock options and ESPP: Stock Option ESPP Year ended January 31, Year ended 2020 2018 January 31, 2020 Expected Term 6.1 - 6.5 years 6.05 years 0.3 - 0.5 years Expected volatility 43% - 44% 41% 40% - 42% Risk-free interest rate 2.33% - 2.52% 1.62% 1.68% - 2.08% Dividend yield —% —% —% Fair value of common stock on grant date $11.67 - $19.36 $4.24 $23.82 - $38.62 There were no stock options granted to employees during the year ended January 31, 2019.

Other Income (Expense), Net

Other Income (Expense), Net	12 Months Ended
	Jan. 31, 2020
Other Income and Expenses [Abstract]
Other Income (Expense), Net	Other Income (Expense), Net Other income (expense), net consist of the following (in thousands): Year ended January 31, 2020 2019 2018 Interest income, net $ 16,190 $ 13,400 $ 3,838 Unrealized gains (losses) on foreign exchange (786 ) (869 ) 1,970 Transaction losses on foreign exchange (1,526 ) (99 ) (1,503 ) Change in fair value of strategic investments 5,599 3,701 27 Other non-operating income, net 1,033 13 249 Other income (expense), net $ 20,510 $ 16,146 $ 4,581

Income Taxes

Income Taxes	12 Months Ended
	Jan. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Loss before income taxes consisted of the following (in thousands): Year ended January 31, 2020 2019 2018 United States $ (294,259 ) $ (85,175 ) $ (100,364 ) Foreign (273,509 ) (52,887 ) (38,906 ) Total $ (567,768 ) $ (138,062 ) $ (139,270 ) The components of the Company’s provision for income tax are as follows (in thousands): Year ended January 31, 2020 2019 2018 Current: Federal $ — $ — $ — State 303 355 20 Foreign 1,919 279 894 Total current 2,222 634 914 Deferred: Federal (120 ) (200 ) — State (23 ) (120 ) — Foreign (1,490 ) 526 (121 ) Total deferred (1,633 ) 206 (121 ) Provision for income taxes $ 589 $ 840 $ 793 A reconciliation of the U.S. federal statutory tax rate to the Company’s provision for income tax is as follows: Year ended January 31, 2020 2019 2018 Tax at statutory federal rate 21.00 % 21.00 % 33.80 % State tax, net of federal benefit 12.68 2.12 2.19 Stock-based compensation 45.16 (2.95 ) (2.29 ) Credits 17.37 6.01 4.34 Foreign rate differential (7.06 ) 9.52 (9.92 ) Other (1.49 ) (3.80 ) (0.55 ) Change in statutory tax rates 0.01 0.13 (17.93 ) Change in valuation allowance (87.77 ) (32.64 ) (10.21 ) Effective tax rate (0.10 )% (0.61 )% (0.57 )% Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The Company’s deferred income tax assets and liabilities consisted of the following (in thousands): Year ended January 31, 2020 2019 2018 Deferred tax assets (liabilities): Accrued liabilities $ 10,646 $ 7,907 $ 3,905 Accounts receivable 93 70 131 Deferred rent — 4,304 1,438 Operating lease liabilities 51,085 — — Operating lease right-of-use assets (42,919 ) — — Net operating losses 415,236 65,385 46,736 Tax credits 120,743 22,116 13,510 Intangible assets 13,176 15,258 (108 ) Property and equipment 2,566 870 1,637 Stock-based compensation 43,182 (2,549 ) (275 ) Other (1,309 ) (684 ) 88 Total gross deferred tax assets 612,499 112,677 67,062 Valuation allowance (611,027 ) (112,693 ) (66,557 ) Total deferred tax assets (liabilities), net $ 1,472 $ (16 ) $ 505 The Company has assessed, based on available evidence, both positive and negative, it is more likely than not that the deferred tax assets will not be utilized, such that a valuation allowance has been recorded, except for certain foreign subsidiaries which generate income. The valuation allowance increased $498.3 million , $46.1 million , and $14.2 million in the years ended January 31, 2020 , 2019 , and 2018 , respectively. As of January 31, 2020 , the Company had U.S. federal and state net operating loss carryforwards of $1.5 billion and $1.2 billion , respectively, available to offset future taxable income. If not utilized, these carryforward losses will expire, in various amounts, for federal and state tax purposes, both beginning in 2029. The Company had no Federal and California capital loss carryforwards as of January 31, 2020 . In addition, the Company had $99.5 million and $54.0 million of federal and state research and development tax credits, respectively, available to offset future taxes as of January 31, 2020 . If not utilized, the federal credits will begin to expire in 2029. California state research and development tax credits may be carried forward indefinitely. Utilization of the net operating loss and tax credit carryforwards may be subject to a substantial annual limitation due to the “ownership change” limitations provided by Section 382 and 383 of the Internal Revenue Code of 1986, as amended, and other similar state provisions. Any annual limitation may result in the expiration of net operating loss and tax credit carryforwards before utilization. The Company is required to inventory, evaluate and measure all uncertain tax positions taken or to be taken on tax returns, and to record liabilities for the amount of such positions that may not be sustained, or may only partially be sustained, upon examination by the relevant taxing authorities. As of January 31, 2020 , the Company’s total unrecognized tax benefits were $37.5 million , exclusive of interest and penalties described below. A reconciliation of the beginning and ending amount of total unrecognized tax benefits is as follows (in thousands): Year ended January 31, 2020 2019 2018 Balance at beginning of period $ 20,484 $ 18,545 $ 17,767 Increase related to prior year tax provisions 1 — 28 Decrease related to prior year tax provisions (2,495 ) (2,076 ) (2,687 ) Increase related to current year tax provisions 19,526 4,022 3,472 Lapse of statute of limitations (21 ) (7 ) (35 ) Balance at end of period $ 37,495 $ 20,484 $ 18,545 As of January 31, 2020 , the unrecognized tax benefits of $37.5 million , if recognized, would no t affect the effective tax rate as it would be offset by the reversal of related deferred tax assets, which are subject to a full valuation allowance. Unrecognized tax benefits that would affect the effective tax rate, if recognized, as of January 31, 2019 and 2018 were no t material. The Company does not expect its gross unrecognized tax benefits to change significantly within the next 12 months. The Company recognizes interest and penalties related to uncertain tax positions in provision for income taxes. Accrued interest and penalties were not material as of January 31, 2020 and 2019 . On December 22, 2017, the legislation commonly referred to as the Tax Cuts and Jobs Act, (the “Tax Act”) was enacted, which contains significant changes to U.S. tax law. The impact of the Tax Act will likely be subject to ongoing technical guidance and accounting interpretation, which the Company will continue to monitor and assess. The Company does not currently anticipate that these changes will have a material impact on its consolidated financial statements. As the Company expands the scale of our international business activities, any changes in the U.S. or foreign taxation of such activities may increase its worldwide effective tax rate and harm our business, results of operations, and financial condition. Under the provisions of the Tax Act, all foreign earnings are subject to U.S. taxation. As a result of the Tax Act, the Company intends to repatriate foreign earnings that have been taxed in the United States to the extent that the foreign earnings are not restricted by local laws and accounting rules. The Company files tax returns in the U.S. (federal and various states) and other foreign jurisdictions. Due to the Company’s U.S. net operating loss carryforwards, its income tax returns generally remain subject to examination by federal and most state tax authorities. As of January 31, 2020, the Company was subject to an income tax audit by Ireland’s Office of the Revenue Commissioner (“Ireland Revenue”). The audit may result in an additional tax charge with related penalties and interest if the Company’s position is not upheld during the audit. On July 27, 2015, the United States Tax Court issued a decision (“Tax Court Decision”) in Altera Corp. v. Commissioner, which concluded that related parties in a cost sharing arrangement are not required to share expenses related to share-based compensation. The Tax Court Decision was appealed by the Commissioner to the Ninth Circuit Court of Appeals (“Ninth Circuit”). On June 7, 2019, the Ninth Circuit issued an opinion (“Altera Ninth Circuit Opinion”) that reversed the Tax Court Decision. On July 22, 2019, the taxpayer requested a rehearing before the full Ninth Circuit and the request was denied on November 12, 2019. The taxpayer has until February 10, 2020 to request a hearing before the Supreme Court of the United States. As a result, the final outcome of the case is uncertain. Starting in the fourth quarter of 2020, the Company has included share-based compensation in its cost share allocation. Due to the full valuation allowance the Company has against its deferred tax assets in the U.S. and Ireland, the Company does not expect the change to have a significant impact to its income tax expense.

Net Loss per Share Attributable

Net Loss per Share Attributable to Slack Common Stockholders	12 Months Ended
	Jan. 31, 2020
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Slack Common Stockholders	Net Loss per Share Attributable to Slack Common Stockholders Basic net loss per share attributable to Slack common stockholders is computed by dividing the net loss attributable to Slack common stockholders by the weighted average number of shares of common stock outstanding during the period. Diluted loss per share is the same as basic loss per share for all years presented because the effects of potentially dilutive items were antidilutive given the Company’s net loss in each period presented. The following table presents the calculation of basic and diluted net loss per share attributable to Slack common stockholders (in thousands, except per share data): Year ended January 31, 2020 2019 2018 Net loss attributable to Slack $ (571,058 ) $ (140,683 ) $ (140,085 ) Less: Deemed dividends to preferred stock stockholders — — 40,883 Net loss attributable to Slack common stockholders $ (571,058 ) $ (140,683 ) $ (180,968 ) Weighted average common shares outstanding 399,461 121,732 122,865 Net loss per share attributable to Slack common stockholders, basic and diluted $ (1.43 ) $ (1.16 ) $ (1.47 ) Since the Company was in a loss position for all periods presented, basic net loss per share attributable to Slack common stockholders is the same as diluted net loss per share attributable to Slack common stockholders as the inclusion of all potential common shares outstanding would have been antidilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows (in thousands) As of January 31, 2020 2019 2018 Convertible preferred stock — 373,372 337,483 Stock options 8,425 18,406 23,720 Unvested early exercised stock options — 115 419 Restricted stock units 42,002 63,114 40,594 Restricted stock awards 1,579 2,289 894 Employee stock purchase plan 814 — — Total antidilutive securities 52,820 457,296 403,110

Geographic Information

Geographic Information	12 Months Ended
	Jan. 31, 2020
Segment Reporting [Abstract]
Geographic Information	Geographic Information See Note 2. Revenues for the Company’s revenue by geographic areas, as determined based on the billing address of its customers. The following table sets forth the Company’s long-lived assets by geographic area, which consist of property and equipment, net and operating lease right-of-use assets (in thousands): As of January 31, 2020 2019 United States $ 256,695 $ 76,768 International 43,475 11,591 Total $ 300,170 $ 88,359

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Jan. 31, 2020
Retirement Benefits [Abstract]
Defined Contribution Plan	Defined Contribution Plan The Company provides a tax-qualified employee savings and retirement plan, commonly known as a 401(k) plan, that allows participating employees in the United States to contribute up to 100% of their pre-tax annual compensation subject to Internal Revenue Service limits. The Company matches employee contributions at a rate of 50% , up to a maximum annual matched contribution of $4,000 per employee. Employee contributions are always fully vested while the matching contributions fully vest following one year of employee’s credited service with the Company. The Company’s matching contributions to its 401(k) plan totaled $5.8 million , $3.7 million , and $2.2 million for the years ended January 31, 2020 , 2019 , and 2018 , respectively.

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Jan. 31, 2020
Accounting Policies [Abstract]
Fiscal Year	The Company’s fiscal year ends on January 31. References to fiscal year 2020, for example, refer to the fiscal year ended January 31, 2020.
Basis of Presentation	The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”), and include the accounts of the Company and its wholly owned and majority-owned subsidiaries.
Consolidation	All intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements include 100% of the accounts of wholly owned and majority-owned subsidiaries and the ownership interest of minority investors is recorded as noncontrolling interest.
Use of Estimates	The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the consolidated financial statements. On a regular basis, management evaluates these estimates and assumptions; however, actual results could materially differ from these estimates. The Company’s most significant estimates and judgments involve revenue recognition, stock-based compensation including the estimation of fair value of common stock, valuation of strategic investments, valuation of acquired goodwill and intangibles from acquisitions, period of benefit for deferred costs, and uncertain tax positions.
Revenue Recognition and Deferred Revenue	Deferred revenue consists of customer billings in advance of revenue being recognized from the Company’s contracts, including credit balances due to the Company’s fair billing policy. Deferred revenue is generally recognized during the succeeding twelve‑month period. The Company derives its revenue from monthly and annual subscription fees earned from customers accessing Slack. The Company’s policy is to exclude sales and other indirect taxes when measuring the transaction price of its subscription agreements. The Company accounts for revenue contracts with customers through the following steps: • Identification of the contract, or contracts, with the customer; • Identification of the performance obligations in the contract; • Determination of the transaction price; • Allocation of the transaction price to the performance obligations in the contract; and • Recognition of the revenue when, or as, the Company satisfies a performance obligation. Subscription revenue is recognized on a straight-line basis over the contractual term of the arrangement beginning on the date that the service is made available to the customer. The Company’s subscription service contracts are generally one month to thirty-six months in duration and are generally non-cancellable. Customers are billed either annually or monthly generally in advance of services. The contracts do not provide customers with the right to take possession of the software supporting Slack. The Company’s arrangements do not contain general rights of return. Amounts that have been invoiced are recorded in accounts receivable and in revenue or deferred revenue, depending on whether the performance obligation has been satisfied. For certain multi-year agreements, revenue recognition may occur in advance of invoicing, resulting in a contract asset when a conditional right to consideration exists and transfer of control for the services rendered. These contract assets are included in prepaid expenses and other current assets. The Company maintains a fair billing policy, under which certain customers maintain a credit balance if they have not used the entirety of the allotment of users for which they have paid during the contractual term of their respective arrangements. These credits, accounted for as a part of deferred revenue, may be carried over to offset billings related to increases in a customer’s number of active users and are not refundable for cash. A majority of the Company’s contracts give a right to bill for additional usage, and this is deemed variable consideration. The variable consideration is allocated to the distinct day the services are completed, as services provided to the additional users are specific to the period that the usage occurs. To the extent that the Company believes it is probable that a significant reversal would not occur, an estimate is made for the revenue associated with incremental usage during a period. The incremental revenue recognized associated with these estimates has not been material for any period presented.
Cost of Revenue	Cost of revenue consists primarily of expenses related to hosting Slack and providing ongoing customer experience support for paid customers, including employee compensation (including stock-based compensation) and other employee-related expenses for customer experience and technical operations staff, payments to outside service providers, third-party hosting costs, payment processing fees and amortization of internally-developed and purchased technology.
Stock-Based Compensation	The Company measures compensation for all stock-based payment awards, including stock options, restricted stock units (“RSUs”), restricted stock awards (“RSAs”), and purchase rights issued under the 2019 Employee Stock Purchase Plan (“ESPP”) granted to employees, directors, and nonemployees, based on the estimated fair value of the awards on the date of grant. The fair value of each stock option and purchase rights issued under the ESPP granted is estimated using the Black-Scholes option pricing model. Stock-based compensation is recognized on a straight-line basis over the requisite service period, except for the RSUs granted under the 2009 Stock Plan (the “2009 Plan”). Under the 2009 Plan, the Company granted RSUs to its employees and directors with both a service-based vesting condition and a performance-based vesting condition. The service-based vesting period for these awards was typically four years with a cliff vesting period of one year and continued vesting quarterly thereafter. The fair value of RSUs was estimated based on the fair market value of t he Company’s common stock at the date of grant. On June 20, 2019 , the performance vesting condition was satisfied upon the completion of the Direct Listing and as a result, the Company recorded cumulative stock-based compensation of $245.1 million related to all then-outstanding RSUs granted under the 2009 Plan. The Company recognizes stock compensation associated with the RSUs granted under the 2009 Plan using the accelerated attribution method over the requisite service period. The Company also granted stock options and RSAs to its employees and directors under the 2009 Plan with a service-based vesting condition. The service-based vesting period for these awards is typically four years with a cliff vesting period of one year and continued vesting monthly thereafter. The fair value of each stock option is estimated using the Black-Scholes option pricing model. The fair value of RSAs is estimated based on the fair market value of t he Company’s common stock at the date of grant. Under the 2019 Stock Option and Incentive Plan (the “2019 Plan”), the Company grants RSUs and stock options to its employees and directors with a service-based vesting condition. The service-based vesting period for these awards is typically four years with a cliff vesting period of one year and continued vesting quarterly thereafter.
Research and Development Costs	Research and development costs are expensed as incurred and consist primarily of personnel costs and allocated overhead.
Advertising Costs	Advertising costs are expensed as incurred and were $38.1 million , $61.7 million , and $35.5 million for the years ended January 31, 2020 , 2019 , and 2018 , respectively. Advertising costs are included in sales and marketing expense in the accompanying consolidated statements of operations.
Income Taxes	The Company recognizes deferred tax liabilities and assets for the expected future tax consequences of temporary differences between the carrying amounts and the tax bases of assets and liabilities. A valuation allowance is established, when necessary, to reduce deferred tax assets to the amount that is more likely than not to be realized. The Company accounts for uncertain tax positions based on an evaluation as to whether it is more likely than not that a tax position will be sustained on audit, including resolution of any related appeals or litigation processes. This evaluation is based on all available evidence and assumes that the appropriate tax authorities have full knowledge of all relevant information concerning the tax position. The tax benefit recognized is based on the largest amount that is greater than 50% likely of being realized upon ultimate settlement. The Company includes interest expense and penalties related to its uncertain tax positions in interest expense and other expense, respectively.
Financial Information about Segments and Geographical Areas	The Company has one business activity and there are no segment managers who are held accountable for operations, results of operations, or plans for levels or components below the consolidated unit level. The Company’s chief operating decision maker is its Chief Executive Officer, who reviews the financial information presented on a consolidated basis for purposes of allocating resources and evaluating the Company’s financial performance. Accordingly, the Company has determined that it operates in a single operating and reporting segment.
Foreign Currency Transaction	The functional currency of the Company’s foreign subsidiaries is the U.S. dollar. Accordingly, each foreign subsidiary remeasures monetary assets and liabilities at period-end exchange rates, while nonmonetary items are remeasured at historical rates. Revenue and expense accounts are remeasured at the average exchange rate in effect during the year. Remeasurement adjustments are recognized in the accompanying consolidated statements of operations as transaction gains or losses in the year of occurrence as other income (expense).
Cash and Cash Equivalents and Restricted Cash	The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. Cash equivalents consist of funds deposited into money market funds, and commercial paper. Restricted cash consists of cash deposited with financial institutions as collateral for the Company’s obligations under its facility leases.
Marketable Securities	The Company determines the appropriate classification of its investments in marketable securities at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its marketable securities as available-for-sale. All of the Company’s available-for-sale investments consist of debt securities, adjusted for amortization of premiums and discounts to maturity and such amortization is included in other income (expense), net. After consideration of the Company’s capital preservation objectives, as well as its liquidity requirements, the Company may sell securities prior to their stated maturities. As the Company views these securities as available to support current operations, it has classified all available-for-sale securities as short-term. The Company carries its available-for-sale securities at fair value and reports the unrealized gains and losses as a component of stockholders’ equity, except for unrealized losses determined to be other than temporary. The Company evaluates its investments periodically for possible other-than-temporary impairment. A decline in fair value below the amortized costs of debt securities is considered an other-than-temporary impairment if the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security before recovery of the entire amortized cost basis. In those instances, an impairment charge equal to the difference between the fair value and the amortized cost basis is recognized in earnings. Regardless of the Company’s intent or requirement to sell a debt security, impairment is considered other than temporary if the Company does not expect to recover the entire amortized cost basis.
Strategic Investments	In December 2015, the Company committed $13.0 million to a newly formed entity, Slack Fund L.L.C. (“Slack Fund”), in exchange for a 52% voting interest. Slack Fund is in the business of purchasing, selling, investing and trading in minority equity and convertible debt securities of privately-held companies that develop applications that have potential for substantial contribution to Slack and its ecosystem. Slack Fund has a duration of ten years and its duration may be extended for three additional years. At dissolution, Slack Fund will be liquidated and the remaining assets of the Slack Fund will be distributed to the investors based on their voting interest. As of January 31, 2020 , the Company had contributed its full commitment of $13.0 million . Additionally, the minority investors in Slack Fund are also investors in the Company. The Company has elected the measurement alternative, defined as cost, less any impairment, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. These investments are valued using significant unobservable inputs or data in inactive markets which require judgment due to the absence of market prices and inherent lack of liquidity. This could result in volatility in other income (expense), net on the accompanying consolidated statements of operations in future periods due to the valuation and timing of identical or similar investments of the same issuer.
Concentration of Credit Risk	Financial instruments that potentially subject the Company to credit risk primarily consist of cash and cash equivalents, restricted cash, marketable securities, and accounts receivable. For cash, cash equivalents, restricted cash, and marketable securities, the Company is exposed to credit risk in the event of default by the financial institutions to the extent of the amounts recorded on the accompanying consolidated balance sheets that are in excess of federal insurance limits. For accounts receivable, the Company is exposed to credit risk in the event of nonpayment by customers to the extent of the amounts recorded on the accompanying consolidated balance sheets.
Fair Value of Financial Instruments	The Company records its financial assets and liabilities at fair value. The carrying amounts of the Company’s financial instruments, which include cash, cash equivalents, restricted cash, accounts receivable, and accounts payable, approximate their fair values due to their short-term nature. The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value, and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows: • Level 1 inputs: Unadjusted quoted prices in active markets for identical assets or liabilities accessible to the reporting entity at the measurement date. • Level 2 inputs: Other than quoted prices included in Level 1 inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the asset or liability. • Level 3 inputs: Unobservable inputs for the asset or liability used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at measurement date. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.
Accounts Receivable, Net	Trade accounts receivable are recorded at invoiced amounts and do not bear interest. The Company generally does not require collateral and performs ongoing credit evaluations of its customers and provides for expected losses. The expectation of collectability is based on the Company’s review of credit profiles of customers, contractual terms and conditions, current economic trends, and historical payment experience. If events or changes in circumstances indicate that specific receivable balances may be impaired, further consideration is given to the collectability of those balances and an allowance is recorded accordingly. Past-due receivable balances are written off when internal collection efforts have been unsuccessful in collecting the amount due.
Property and Equipment, Net	Property and equipment, net is stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful life of the related asset, which is typically two years for computer equipment and software, five years for furniture and fixtures, and in the case of leasehold improvements, the remaining term of the lease, unless the useful life of the asset is shorter. Maintenance and repairs are charged to expense as incurred.
Internal-Use Software Development Costs	The Company capitalizes qualifying internal-use software development costs that are incurred during the application development stage. Capitalization of costs begins when two criteria are met: (i) the preliminary project stage is completed and (ii) it is probable that the software will be completed and used for its intended function. Capitalization ceases when the software is substantially complete and ready for its intended use, including the completion of all significant testing. Costs related to preliminary project activities and post-implementation operating activities are expensed as incurred. Capitalized costs are included in property and equipment. These costs are amortized over the estimated useful life of the software (generally two years ) on a straight-line basis. Management evaluates the useful life of these assets on an annual basis and tests for impairment whenever events or changes in circumstances occur that could impact the recoverability of these assets. The amortization of costs related to the platform applications is included in cost of revenue.
Business Combinations	The Company applies the acquisition method of accounting for business combinations. Under this method of accounting, all assets acquired and liabilities assumed are recorded at their respective fair values at the date of the acquisition. Determining the fair value of assets acquired and liabilities assumed requires management’s judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, discount rates, intangibles, and other asset lives, among other items. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Market participants are assumed to be buyers and sellers in the principal (most advantageous) market for the asset or liability. Additionally, fair value measurements for an asset assume the highest and best use of that asset by market participants. As a result, the Company may be required to value the acquired assets at fair value measures that do not reflect its intended use of those assets. Use of different estimates and judgments could yield different results. Any excess of the purchase price over the fair value of the net assets acquired is recognized as goodwill. If the fair value of net assets acquired exceeds the fair value of purchase price, a gain on bargain purchase is recognized within the accompanying consolidated statements of operations. Although the Company believes the assumptions and estimates it has made are reasonable and appropriate, they are based in part on historical experience and information that may be obtained from the management of the acquired company and are inherently uncertain. During the measurement period, which may be up to one year from the acquisition date, the Company may record adjustments to the assets acquired and liabilities assumed with the corresponding offset to goodwill for facts and considerations that were known at the acquisition date. Upon the conclusion of the measurement period or final determination of the values of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded within the accompanying consolidated statements of operations.
Accounting for Impairment of Long-Lived Assets	The Company evaluates long-lived assets, such as property and equipment and acquired intangibles, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets held and used is measured by comparison of the carrying amount of an asset or an asset group to estimated undiscounted future net cash flows expected to be generated by the asset or asset group. If the carrying amount of an asset exceeds these estimated future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the assets exceeds the fair value of the asset or asset group, based on discounted cash flows.
Goodwill	Goodwill is not amortized, but rather is tested for impairment at least annually or more frequently if indicators of impairment are present. The Company operates as one
Operating Leases	The Company leases real estate facilities under non-cancelable operating leases with various expiration dates through fiscal year 2031. The Company determines if an arrangement contains a lease at inception based on whether there is an identified property, plant or equipment and whether the Company controls the use of the identified asset throughout the period of use. The Company adopted the Accounting Standard Update (“ASU”) No. 2016-02, Leases ( Topic 842 ) on November 1, 2019. Operating leases are included in operating lease right-of-use (“ROU”) assets and in operating lease liabilities in the accompanying consolidated balance sheets. Operating lease ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and lease liabilities are recognized at the lease inception date based on the present value of lease payments over the lease term discounted based on the more readily determinable of (i) the rate implicit in the lease or (ii) the Company’s incremental borrowing rate (which is the estimated rate the Company would be required to pay for a collateralized borrowing equal to the total lease payments over the term of the lease). Because the Company’s operating leases generally do not provide an implicit rate, the Company estimates its incremental borrowing rate based on the information available at lease commencement date for borrowings with a similar term. The Company’s operating lease ROU assets are measured based on the corresponding operating lease liability adjusted for (i) payments made to the lessor at or before the commencement date, (ii) initial direct costs incurred and (iii) tenant incentives under the lease. The Company does not assume renewals or early terminations unless it is reasonably certain to exercise these options at commencement. The Company does not allocate consideration between lease and non-lease components. Variable lease payments are recognized in the period in which the obligation for those payments are incurred. In addition, the Company does not recognize ROU assets or lease liabilities for leases with a term of 12 months or less of all asset classes. Operating lease expense is recognized on a straight-line basis over the lease term. Lease accounting prior to the adoption of Topic 842
Deferred Contract Acquisition Costs, Net	Sales commissions earned by the Company’s sales force are considered to be incremental and recoverable costs of obtaining a contract with a customer. As a result, these amounts have been capitalized as deferred contract acquisition costs within prepaid expenses and other current assets and other assets on the accompanying consolidated balance sheets. Deferred contract acquisition costs are typically amortized over a period of benefit of four years
Recently Adopted Accounting Standards and Recently Issued Accounting Standards Not Yet Adopted	In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments, which requires an entity to utilize a new impairment model known as the current expected credit loss (“CECL”) model to estimate its lifetime “expected credit loss” and record an allowance that, when deducted from the amortized cost basis of the financial asset, presents the net amount expected to be collected on the financial asset. The CECL model is expected to result in more timely recognition of credit losses. This guidance also requires new disclosures for financial assets measured at amortized cost, loans and available-for-sale debt securities. ASU No. 2016-13 is effective for public companies for annual periods beginning after December 15, 2019, including interim periods within those fiscal years. Entities will apply the standard’s provisions as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The Company does not believe this standard will have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement , which modifies the disclosure requirements on fair value measurements in Topic 820, Fair Value Measurement . The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. This standard is effective for all entities for annual reporting periods beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. The Company does not believe this standard will have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which aligns the accounting for implementation costs incurred in a hosting arrangement that is a service contract with the accounting for implementation costs incurred to develop or obtain internal-use software under ASC 350-40, in order to determine which costs to capitalize and recognize as an asset and which costs to expense. ASU No. 2018-15 is effective for annual reporting periods beginning after December 15, 2019, and interim periods within those years, and can be applied either prospectively to implementation costs incurred after the date of adoption or retrospectively to all arrangements. The Company does not believe this standard will have a material impact on its consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740 and also improve consistent application of other areas by clarifying and amending existing guidance. This standard is effective for annual reporting periods beginning after December 15, 2020, and interim periods within those years, and early adoption is permitted. Certain amendments of this standard may be adopted on a retrospective basis, modified retrospective basis or prospective basis. The Company is currently evaluating the impact this standard will have on its consolidated financial statements. In February 2016, the Financial Accounting Standards Board (“FASB”) issued Topic 842, Leases , which generally requires companies to recognize operating and financing lease liabilities and corresponding ROU assets on the balance sheet. The Company early adopted the standard as of November 1, 2019, using the modified retrospective approach and has elected to use the optional transition method which allows the Company to apply the guidance of ASC 840, including disclosure requirements, in the comparative periods presented. The Company does not believe reflecting the adoption as of February 1, 2019 would have materially impacted its consolidated balance sheet as of January 31, 2020 or its results of operations or operating cash flows for the year then ended. In addition, the Company elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed the Company to carry forward the historical lease classification related to agreements entered prior to adoption. The adoption of the new standard resulted in recognition of operating lease ROU assets and operating lease liabilities of $198.4 million and $228.4 million , respectively, as of November 1, 2019. There was no cumulative impact of transition to retained earnings as of the adoption date. The standard did not materially impact the accompanying consolidated statements of operations and had no impact on the accompanying consolidated statements of cash flows. In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (Subtopic 825-10) and issued a subsequent amendment to the initial guidance within ASU 2018-03, which requires entities to carry all investments in equity securities at fair value and recognize any changes in fair value in net income. Under the standard, equity investments that do not have readily determinable fair values and do not qualify for the net asset value practical expedient are eligible for the measurement alternative. For our equity investments in private companies, we will elect the measurement alternative, defined as cost, less any impairment, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. The guidance was effective for the Company’s fiscal year beginning February 1, 2018 on a prospective basis for the amendments related to equity securities without readily determinable fair values existing as of the date of adoption. The Company adopted the new standard as of February 1, 2018 and it did not have a material impact on its consolidated financial statements. The impact of the new standard going forward could result in volatility in other income (expense), net on the accompanying consolidated statements of operations in future periods due to the valuation and timing of identical or similar investments of the same issuer. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740) Intra-Entity Transfers of Assets other than Inventory, which amends the guidance used in the recognition of current and deferred income taxes for an intra-entity transfer of assets other than inventory. The guidance requires an entity recognize the income tax consequences of an intra-entity transfer of an asset other than inventory at the time of transfer. The guidance is effective for annual and interim reporting periods beginning after December 15, 2017 for public entities. The Company adopted ASU No. 2016-06 as of February 1, 2018. The adoption of this guidance did not have a material impact on the accompanying consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business , which clarifies the definition of a business to determine when a transaction is accounted for as an acquisition (or disposal) of a set of assets or a business. The Company adopted ASU No. 2017-01 as of February 1, 2018, utilizing the prospective method of transition. The adoption of the new standard did not have any impact on the accompanying consolidated financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation: Scope of Modification Accounting , which clarifies when a change to the terms or conditions of a stock-based payment award must be accounted for as a modification. This guidance requires modification accounting if the fair value, vesting condition, or the classification of the award is not the same immediately before and after a change to the terms and conditions of the award. This standard was effective for annual periods beginning after December 15, 2017 and early adoption was permitted. The Company adopted ASU No. 2017-09 as of February 1, 2018, utilizing the prospective method of transition. The adoption of this guidance did not have a material impact on the accompanying consolidated financial statements. In February 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income , which allows a reclassification of the income tax effects of the U.S. Tax Cuts and Jobs Act (the “Tax Act”) on items within accumulated other comprehensive income to retained earnings. This standard became effective for all entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The new guidance may be applied retrospectively to each period in which the effect of the Tax Reform Act is recognized in the period of adoption. The Company adopted ASU No. 2018-02 as of February 1, 2019. The adoption of this standard did not have a material impact on the accompanying consolidated financial statements. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting , which simplifies the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees, with certain exceptions. This standard is effective for public business entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. For all other entities, this ASU is effective for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted, but no earlier than the adoption date of Topic 606. The Company adopted ASU No. 2018-07 as of February 1, 2019. The adoption of the new standard did not have any impact on the accompanying consolidated financial statements.

Description of Business and S_3

Description of Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Jan. 31, 2020
Accounting Policies [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash to Statements of Cash Flows	A reconciliation of cash, cash equivalents and restricted cash to the accompanying consolidated statements of cash flows is as follows (in thousands): As of January 31, 2020 2019 Cash and cash equivalents $ 498,999 $ 180,770 Restricted cash 38,490 20,490 Total cash, cash equivalents and restricted cash $ 537,489 $ 201,260
Reconciliation of Cash, Cash Equivalents and Restricted Cash to Statements of Cash Flows	A reconciliation of cash, cash equivalents and restricted cash to the accompanying consolidated statements of cash flows is as follows (in thousands): As of January 31, 2020 2019 Cash and cash equivalents $ 498,999 $ 180,770 Restricted cash 38,490 20,490 Total cash, cash equivalents and restricted cash $ 537,489 $ 201,260

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Jan. 31, 2020
Revenue from Contract with Customer [Abstract]
Schedule of Contract Liabilities	Contract liabilities consist of deferred revenue. The changes in deferred revenue were as follows (in thousands): Year Ended January 31, 2020 Balance, beginning of period $ 241,873 Billings 765,263 Revenue (630,422 ) Balance, end of period $ 376,714
Schedule of Revenues by Geographical Area	The following table shows the Company’s revenue by geographic areas, as determined based on the billing address of its customers (in thousands): Year ended January 31, 2020 2019 2018 United States $ 394,716 $ 255,155 $ 144,720 International 235,706 145,397 75,824 Total $ 630,422 $ 400,552 $ 220,544

Cash, Cash Equivalents and Ma_2

Cash, Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Jan. 31, 2020
Cash and Cash Equivalents [Abstract]
Schedule of Cash and Cash Equivalents and Marketable Securities	The carrying amounts and estimated fair value of cash, cash equivalents, and marketable securities consisted of the following (in thousands): As of January 31, 2020 2019 Cash and cash equivalents: Cash $ 71,593 $ 62,033 Money market funds 357,524 118,737 Commercial paper 69,882 — Cash and cash equivalents $ 498,999 $ 180,770 Marketable securities: Commercial paper $ 19,795 $ 17,462 U.S. agency securities 29,515 44,879 U.S. government securities 97,172 370,574 International government securities 8,115 36,734 Corporate bonds 114,996 190,652 Total marketable securities $ 269,593 $ 660,301 The following tables summarize unrealized gains and losses related to cash equivalents and marketable securities on the Company’s consolidated balance sheets (in thousands): As of January 31, 2020 Amortized Unrealized Unrealized Fair value Cash and cash equivalents: Cash $ 71,593 $ — $ — $ 71,593 Money market funds 357,524 — — 357,524 Commercial paper 69,891 — (9 ) 69,882 Total cash and cash equivalents 499,008 — (9 ) 498,999 Marketable securities: Commercial paper 19,799 4 (8 ) 19,795 U.S. agency securities 29,460 55 — 29,515 U.S. government securities 97,071 102 (1 ) 97,172 International government securities 8,109 6 — 8,115 Corporate bonds 114,871 139 (14 ) 114,996 Total marketable securities 269,310 306 (23 ) 269,593 Total cash, cash equivalents and marketable securities $ 768,318 $ 306 $ (32 ) $ 768,592 As of January 31, 2019 Amortized Unrealized Unrealized Fair value Cash and cash equivalents: Cash $ 62,033 $ — $ — $ 62,033 Money market funds 118,737 — — 118,737 Total cash and cash equivalents 180,770 — — 180,770 Marketable securities: Commercial paper 17,461 1 — 17,462 U.S. agency securities 44,886 7 (14 ) 44,879 U.S. government securities 370,498 143 (67 ) 370,574 International government securities 36,810 — (76 ) 36,734 Corporate bonds 190,944 — (292 ) 190,652 Total marketable securities 660,599 151 (449 ) 660,301 Total cash, cash equivalents and marketable securities $ 841,369 $ 151 $ (449 ) $ 841,071
Schedule of Marketable Securities by Contractual Maturity	The following table classifies marketable securities by contractual maturities (in thousands): As of January 31, 2020 2019 Due in one year $ 190,344 $ 506,297 Due in one to two years 79,249 154,004 Total $ 269,593 $ 660,301

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Jan. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments Measured at Fair Value on a Recurring Basis	The following table provides the financial instruments measured at fair value on a recurring basis, within the fair value hierarchy (in thousands): As of January 31, 2020 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 357,524 $ — $ — $ 357,524 Commercial paper — 69,882 — 69,882 Total cash equivalents $ 357,524 $ 69,882 $ — $ 427,406 Marketable securities: Commercial paper $ — $ 19,795 $ — $ 19,795 U.S. agency securities — 29,515 — 29,515 U.S. government securities — 97,172 — 97,172 International government securities — 8,115 — 8,115 Corporate bonds — 114,996 — 114,996 Total marketable securities $ — $ 269,593 $ — $ 269,593 Noncurrent assets: Strategic investments $ — $ — $ 28,814 $ 28,814 As of January 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 118,737 $ — $ — $ 118,737 Total cash equivalents $ 118,737 $ — $ — $ 118,737 Marketable securities: Commercial paper $ — $ 17,462 $ — $ 17,462 U.S. agency securities — 44,879 — 44,879 U.S. government securities — 370,574 — 370,574 International government securities — 36,734 — 36,734 Corporate bonds — 190,652 — 190,652 Total marketable securities $ — $ 660,301 $ — $ 660,301 Noncurrent assets: Strategic investments $ — $ — $ 12,334 $ 12,334
Schedule of Level 3 Assets Measured at Fair Value on Recurring Basis	The following table presents additional information about Level 3 assets measured at fair value on a recurring basis (in thousands): Year ended January 31, 2020 2019 Balance at beginning of period $ 12,334 $ 7,623 Purchases 14,132 2,276 Proceeds from liquidation (3,251 ) (1,266 ) Realized gains (losses) 2,285 (131 ) Unrealized gains relating to investments still held at reporting date 3,314 3,832 Balance at end of period $ 28,814 $ 12,334

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Jan. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment by Category	The following is a summary of the Company’s property and equipment by category (in thousands): As of January 31, 2020 2019 Computer equipment and software $ 3,183 $ 2,222 Furniture and fixtures 27,384 19,693 Capitalized internal-use software costs 4,241 4,241 Leasehold improvements 98,770 86,258 Construction in progress 10,345 6,076 Property and equipment, gross 143,923 118,490 Less: accumulated depreciation and amortization (41,583 ) (30,131 ) Property and equipment, net $ 102,340 $ 88,359

Operating Leases (Tables)

Operating Leases (Tables)	12 Months Ended
	Jan. 31, 2020
Leases [Abstract]
Schedule of Operating Leases, Other Information	The following table sets forth a summary of and other information pertaining to the Company’s operating leases for the fourth quarter of fiscal year 2020 (dollars in thousands): Operating cash flows used for operating leases $ 9,495 Operating lease liabilities arising from obtaining ROU assets $ 4,832 Weighted average remaining terms 8.3 years Weighted average discount rate 5.2 %
Schedule of Maturities of Operating Lease Liabilities	Future minimum lease payments under non-cancelable operating leases with initial lease terms in excess of one year as of January 31, 2020 as follows (in thousands): Year ending January 31, 2021 $ 37,633 2022 50,472 2023 51,276 2024 49,723 2025 52,373 Thereafter 254,256 Gross lease payments 495,733 Less: Imputed interest (64,683 ) Less: Tenant improvement receivables (14,381 ) Less: Leases executed but not yet commenced (189,826 ) Present value of lease liabilities $ 226,843

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Jan. 31, 2020
Business Combinations [Abstract]
Schedule of Allocation of Purchase Price	A summary of the allocation of the purchase price is presented as follows (in thousands): Identified intangible asset - developed technology $ 5,300 Goodwill 37,795 Net tangible assets acquired 234 Total purchase price $ 43,329
Schedule of Intangible Assets Acquired	Following are the details of all intangible assets acquired as a result of acquisitions for the year ended January 31, 2019 (dollars in thousands): Amount Weighted Customer relationships $ 9,100 7 years Developed technology 6,700 3 years Assembled workforce 1,198 2 years Fair value of intangible assets acquired $ 16,998 5 years

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets, Net (Tables)	12 Months Ended
	Jan. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in Carrying Amount of Goodwill	The following table reflects the changes in the carrying amount of goodwill (in thousands): Year ended January 31, 2020 2019 Balance at beginning of year $ 48,598 $ 8,653 Additions due to acquisitions — 39,945 Balance at end of year $ 48,598 $ 48,598
Schedule of Intangible Assets	Intangible assets as of January 31, 2020 and 2019 consist of the following (in thousands, except years): As of January 31, 2020 Weighted-average Gross carrying Accumulated Net carrying Customer relationships 5.5 years $ 9,100 $ 2,004 $ 7,096 Developed technology 1.6 years 8,527 4,976 3,551 Patents 4.9 years 2,500 42 2,458 Assembled workforce 0.7 years 1,198 773 425 Total $ 21,325 $ 7,795 $ 13,530 As of January 31, 2019 Weighted-average remaining amortization period Gross carrying amount Accumulated amortization Net carrying amount Customer relationships 6.5 years $ 9,100 $ 704 $ 8,396 Developed technology 2.6 years 8,527 2,743 5,784 Assembled workforce 1.7 years 1,198 175 1,023 Total $ 18,825 $ 3,622 $ 15,203
Schedule of Expected Amortization Expense Related to Intangible Assets	As of January 31, 2020 , expected amortization expense relating to intangible assets for each of the next five years and thereafter is as follows (in thousands): Year ending January 31, 2021 $ 4,458 2022 3,118 2023 1,800 2024 1,800 2025 1,758 Thereafter 596 Total $ 13,530

Stockholders Equity (Tables)

Stockholders Equity (Tables)	12 Months Ended
	Jan. 31, 2020
Equity [Abstract]
Schedule of Reserved Shares of Common Stock for Future Issuance	The Company had reserved shares of common stock for future issuance as follows (in thousands): As of January 31, 2020 Stock options outstanding 8,425 Restricted stock units outstanding 42,002 Shares available for future grants 59,200 Shares available for ESPP 8,664 Total 118,291 At January 31, 2019, convertible preferred stock consisted of the following (in thousands): Shares Net Liquidation preference Authorized Outstanding Series A 84,751 84,751 $ 8,011 $ 8,060 Series B 43,320 43,320 10,674 10,700 Series C 64,805 64,805 42,678 42,750 Series D 47,059 42,490 108,266 108,350 Series D-1 1,235 1,235 2,561 3,149 Series E 26,787 22,602 134,832 135,000 Series E-1 6,047 6,047 37,940 37,950 Series F 19,867 19,867 154,957 155,000 Series F-1 6,793 6,793 52,940 53,000 Series G 24,718 24,718 229,648 230,000 Series G-1 2,149 2,149 20,000 20,000 Series G-2 17,241 17,241 150,000 150,000 Series G-3 1,465 1,465 12,714 8,700 Series H 35,150 33,470 398,082 398,468 Series H-1 9,202 2,419 28,798 28,798 Total 390,589 373,372 $ 1,392,101 $ 1,389,925
Schedule of Stock Options Activity	A summary of stock option activity under the 2009 Plan and 2019 Plan and related information is as follows (in thousands, except years and per share data): Number of stock options outstanding Weighted-average exercise price per share Weighted-average remaining contractual term (In years) Aggregate intrinsic value Outstanding at January 31, 2019 18,406 $ 0.94 6.12 $ 177,012 Granted 3,663 10.58 Exercised (13,268 ) 1.04 Canceled (376 ) 7.67 Outstanding at January 31, 2020 8,425 $ 4.68 6.27 $ 135,224 Stock options vested and exercisable at January 31, 2020 5,342 $ 1.44 4.96 $ 103,049 Stock options vested and expected to vest at January 31, 2020 8,425 $ 4.68 6.27 $ 135,224
Schedule of Restricted Stock Units and Restricted Stock Activity	A summary of RSUs and RSAs activity under the 2009 Plan and 2019 Plan is as follows (in thousands, except per share data): Restricted stock units Restricted stock awards Number of shares Weighted-average grant date fair value (per share) Number of shares Weighted-average grant date fair value (per share) Unvested at January 31, 2019 63,114 $ 4.87 2,289 $ 7.23 Granted 23,804 18.93 505 13.60 Released (40,318 ) 4.84 (1,205 ) 7.74 Canceled (4,598 ) 8.45 (10 ) 2.37 Unvested at January 31, 2020 42,002 $ 12.48 1,579 $ 8.91
Schedule of Stock-Based Compensation Expense	A summary of the stock-based compensation related to the stock transfers recorded in the accompanying consolidated statements of operations is as follows (in thousands): Year ended January 31, 2020 2019 2018 Cost of revenue $ — $ 533 $ — Research and development — 6,228 — Sales and marketing — 1,707 — General and administrative — 6,353 — Total $ — $ 14,821 $ — A summary of the stock-based compensation excluding tender offers and stock transfers recorded in the accompanying consolidated statements of operations is as follows (in thousands): Year ended January 31, 2020 2019 2018 Cost of revenue $ 16,013 $ 199 $ 239 Research and development 226,507 3,720 4,586 Sales and marketing 98,797 970 1,495 General and administrative 85,207 3,422 2,389 Total $ 426,524 $ 8,311 $ 8,709 A summary of the stock-based compensation related to the tender offers and repurchases, recorded in the accompanying consolidated statements of operations is as follows (in thousands): Year ended January 31, 2020 2019 2018 Cost of revenue $ — $ — $ 252 Research and development — — 30,674 Sales and marketing — — 6,549 General and administrative — — 1,899 Total $ — $ — $ 39,374
Schedule of Assumptions Used in Valuation of Stock Options	The following assumptions used in the valuation of stock options and ESPP: Stock Option ESPP Year ended January 31, Year ended 2020 2018 January 31, 2020 Expected Term 6.1 - 6.5 years 6.05 years 0.3 - 0.5 years Expected volatility 43% - 44% 41% 40% - 42% Risk-free interest rate 2.33% - 2.52% 1.62% 1.68% - 2.08% Dividend yield —% —% —% Fair value of common stock on grant date $11.67 - $19.36 $4.24 $23.82 - $38.62
Schedule of Assumptions Used in Valuation of ESPP	The following assumptions used in the valuation of stock options and ESPP: Stock Option ESPP Year ended January 31, Year ended 2020 2018 January 31, 2020 Expected Term 6.1 - 6.5 years 6.05 years 0.3 - 0.5 years Expected volatility 43% - 44% 41% 40% - 42% Risk-free interest rate 2.33% - 2.52% 1.62% 1.68% - 2.08% Dividend yield —% —% —% Fair value of common stock on grant date $11.67 - $19.36 $4.24 $23.82 - $38.62

Other Income (Expense), Net (Ta

Other Income (Expense), Net (Tables)	12 Months Ended
	Jan. 31, 2020
Other Income and Expenses [Abstract]
Schedule of Other Income (Expense), Net	Other income (expense), net consist of the following (in thousands): Year ended January 31, 2020 2019 2018 Interest income, net $ 16,190 $ 13,400 $ 3,838 Unrealized gains (losses) on foreign exchange (786 ) (869 ) 1,970 Transaction losses on foreign exchange (1,526 ) (99 ) (1,503 ) Change in fair value of strategic investments 5,599 3,701 27 Other non-operating income, net 1,033 13 249 Other income (expense), net $ 20,510 $ 16,146 $ 4,581

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Jan. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Loss Before Income Taxes	Loss before income taxes consisted of the following (in thousands): Year ended January 31, 2020 2019 2018 United States $ (294,259 ) $ (85,175 ) $ (100,364 ) Foreign (273,509 ) (52,887 ) (38,906 ) Total $ (567,768 ) $ (138,062 ) $ (139,270 )
Schedule of Components of Income Tax Expense (Benefit)	The components of the Company’s provision for income tax are as follows (in thousands): Year ended January 31, 2020 2019 2018 Current: Federal $ — $ — $ — State 303 355 20 Foreign 1,919 279 894 Total current 2,222 634 914 Deferred: Federal (120 ) (200 ) — State (23 ) (120 ) — Foreign (1,490 ) 526 (121 ) Total deferred (1,633 ) 206 (121 ) Provision for income taxes $ 589 $ 840 $ 793
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the U.S. federal statutory tax rate to the Company’s provision for income tax is as follows: Year ended January 31, 2020 2019 2018 Tax at statutory federal rate 21.00 % 21.00 % 33.80 % State tax, net of federal benefit 12.68 2.12 2.19 Stock-based compensation 45.16 (2.95 ) (2.29 ) Credits 17.37 6.01 4.34 Foreign rate differential (7.06 ) 9.52 (9.92 ) Other (1.49 ) (3.80 ) (0.55 ) Change in statutory tax rates 0.01 0.13 (17.93 ) Change in valuation allowance (87.77 ) (32.64 ) (10.21 ) Effective tax rate (0.10 )% (0.61 )% (0.57 )%
Schedule of Deferred Tax Assets and Liabilities	The Company’s deferred income tax assets and liabilities consisted of the following (in thousands): Year ended January 31, 2020 2019 2018 Deferred tax assets (liabilities): Accrued liabilities $ 10,646 $ 7,907 $ 3,905 Accounts receivable 93 70 131 Deferred rent — 4,304 1,438 Operating lease liabilities 51,085 — — Operating lease right-of-use assets (42,919 ) — — Net operating losses 415,236 65,385 46,736 Tax credits 120,743 22,116 13,510 Intangible assets 13,176 15,258 (108 ) Property and equipment 2,566 870 1,637 Stock-based compensation 43,182 (2,549 ) (275 ) Other (1,309 ) (684 ) 88 Total gross deferred tax assets 612,499 112,677 67,062 Valuation allowance (611,027 ) (112,693 ) (66,557 ) Total deferred tax assets (liabilities), net $ 1,472 $ (16 ) $ 505
Schedule of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of total unrecognized tax benefits is as follows (in thousands): Year ended January 31, 2020 2019 2018 Balance at beginning of period $ 20,484 $ 18,545 $ 17,767 Increase related to prior year tax provisions 1 — 28 Decrease related to prior year tax provisions (2,495 ) (2,076 ) (2,687 ) Increase related to current year tax provisions 19,526 4,022 3,472 Lapse of statute of limitations (21 ) (7 ) (35 ) Balance at end of period $ 37,495 $ 20,484 $ 18,545

Net Loss per Share Attributab_2

Net Loss per Share Attributable to Slack Common Stockholders (Tables)	12 Months Ended
	Jan. 31, 2020
Earnings Per Share [Abstract]
Schedule Calculation of Basic and Diluted Net Loss Per Share	The following table presents the calculation of basic and diluted net loss per share attributable to Slack common stockholders (in thousands, except per share data): Year ended January 31, 2020 2019 2018 Net loss attributable to Slack $ (571,058 ) $ (140,683 ) $ (140,085 ) Less: Deemed dividends to preferred stock stockholders — — 40,883 Net loss attributable to Slack common stockholders $ (571,058 ) $ (140,683 ) $ (180,968 ) Weighted average common shares outstanding 399,461 121,732 122,865 Net loss per share attributable to Slack common stockholders, basic and diluted $ (1.43 ) $ (1.16 ) $ (1.47 )
Schedule of Potentially Dilutive Securities Excluded from Diluted Per Share Calculations	Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows (in thousands) As of January 31, 2020 2019 2018 Convertible preferred stock — 373,372 337,483 Stock options 8,425 18,406 23,720 Unvested early exercised stock options — 115 419 Restricted stock units 42,002 63,114 40,594 Restricted stock awards 1,579 2,289 894 Employee stock purchase plan 814 — — Total antidilutive securities 52,820 457,296 403,110

Geographic Information (Tables)

Geographic Information (Tables)	12 Months Ended
	Jan. 31, 2020
Segment Reporting [Abstract]
Schedule of Revenue and Tangible Long-Lived Assets by Geographical Area	The following table sets forth the Company’s long-lived assets by geographic area, which consist of property and equipment, net and operating lease right-of-use assets (in thousands): As of January 31, 2020 2019 United States $ 256,695 $ 76,768 International 43,475 11,591 Total $ 300,170 $ 88,359

Description of Business and S_4

Description of Business and Summary of Significant Accounting Policies - Narrative (Details)	Jun. 20, 2019USD ($)	Dec. 31, 2015USD ($)	Jan. 31, 2020USD ($)segmentreporting_unit	Jan. 31, 2019USD ($)	Jan. 31, 2018USD ($)	Jan. 31, 2020USD ($)	Nov. 01, 2019USD ($)
Subsidiary, Sale of Stock [Line Items]
Advertising costs			$ 38,100,000	$ 61,700,000	$ 35,500,000
Number of operating segments | segment			1
Number of reportable segments | segment			1
Long-lived asset impairment charges			$ 0	0	0
Number of reporting units | reporting_unit			1
Goodwill impairment charges			$ 0	0	0
Deferred rent credit				18,700,000
Deferred costs amortization period			4 years			4 years
Impairment loss related to deferred costs			$ 0	0	$ 0
Operating lease right-of-use assets			197,830,000			$ 197,830,000
Operating lease liabilities			$ 226,843,000			226,843,000
Accounting Standards Update 2016-02
Subsidiary, Sale of Stock [Line Items]
Operating lease right-of-use assets							$ 198,400,000
Operating lease liabilities							$ 228,400,000
Other Liabilities
Subsidiary, Sale of Stock [Line Items]
Deferred rent credit				$ 17,900,000
Computer equipment and software
Subsidiary, Sale of Stock [Line Items]
Useful life of property and equipment			2 years
Furniture and fixtures
Subsidiary, Sale of Stock [Line Items]
Useful life of property and equipment			5 years
Internal-Use Software Development Costs
Subsidiary, Sale of Stock [Line Items]
Useful life of property and equipment			2 years
Slack Fund L.L.C.
Subsidiary, Sale of Stock [Line Items]
Agreed upon commitments to acquire interest in entity		$ 13,000,000
Voting interest acquired (as percent)		52.00%
Contributions made to acquired entity since inception						$ 13,000,000
Restricted stock units
Subsidiary, Sale of Stock [Line Items]
Compensation expense	$ 245,100,000
Restricted stock units | 2009 Stock Plan
Subsidiary, Sale of Stock [Line Items]
Vesting period			4 years
Restricted stock units | 2019 Stock Option and Incentive Plan
Subsidiary, Sale of Stock [Line Items]
Vesting period			4 years
Restricted stock awards | 2009 Stock Plan
Subsidiary, Sale of Stock [Line Items]
Vesting period			4 years
Cliff Vesting Period | Restricted stock units | 2009 Stock Plan
Subsidiary, Sale of Stock [Line Items]
Vesting period			1 year
Cliff Vesting Period | Restricted stock awards | 2009 Stock Plan
Subsidiary, Sale of Stock [Line Items]
Vesting period			1 year
Cliff Vesting Period | Restricted stock awards | 2019 Stock Option and Incentive Plan
Subsidiary, Sale of Stock [Line Items]
Vesting period			1 year
Direct Listing
Subsidiary, Sale of Stock [Line Items]
Financial advisory service, audit and legal fees associated with direct listing			$ 30,400,000
Slack Fund L.L.C.
Subsidiary, Sale of Stock [Line Items]
Liquidation period for entity acquired		10 years
Liquidation extension period for entity acquired		3 years
Minimum
Subsidiary, Sale of Stock [Line Items]
Subscription service contract term			1 month
Maximum
Subsidiary, Sale of Stock [Line Items]
Subscription service contract term			36 months

Description of Business and S_5

Description of Business and Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash to Statements of Cash Flows (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 498,999	$ 180,770
Restricted cash	38,490	20,490
Total cash, cash equivalents and restricted cash	$ 537,489	$ 201,260	$ 138,063	$ 117,081

Revenue - Schedule of Contract

Revenue - Schedule of Contract Liabilities (Details) $ in Thousands	12 Months Ended
	Jan. 31, 2020USD ($)
Contract With Customer, Liability [Roll Forward]
Balance, beginning of period	$ 241,873
Billings	765,263
Revenue	(630,422)
Balance, end of period	$ 376,714

Revenue - Narrative (Details)

Revenue - Narrative (Details) - USD ($)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Revenue from Contract with Customer [Abstract]
Percentage of revenue recognized from deferred revenues	36.00%
Deferred incremental costs of obtaining a contract	$ 23,600,000	$ 15,800,000	$ 4,700,000
Deferred commissions, net included in prepaid expenses and other current assets	11,200,000	5,300,000
Deferred commissions net, included in other assets	21,400,000	11,900,000
Amortization of deferred contract acquisition costs	8,153,000	3,154,000	611,000
Impairment loss related to deferred costs	$ 0	$ 0	$ 0

Revenue - Remaining Performance

Revenue - Remaining Performance Obligations (Details) $ in Millions	Jan. 31, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Future estimated revenue related to unsatisfied or partially satisfied performance obligations	$ 328.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-02-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations expected to be recognized (as a percent)	57.00%
Performance obligations expected to be satisfied, expected timing	12 months

Revenue - Schedule of Revenue b

Revenue - Schedule of Revenue by Geographic Areas (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 630,422	$ 400,552	$ 220,544
United States
Disaggregation of Revenue [Line Items]
Total revenues	394,716	255,155	144,720
International
Disaggregation of Revenue [Line Items]
Total revenues	$ 235,706	$ 145,397	$ 75,824

Cash, Cash Equivalents and Ma_3

Cash, Cash Equivalents and Marketable Securities - Carrying Value and Fair Value of Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	$ 498,999	$ 180,770
Total marketable securities	269,593	660,301
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Total marketable securities	19,795	17,462
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Total marketable securities	29,515	44,879
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Total marketable securities	97,172	370,574
International government securities
Debt Securities, Available-for-sale [Line Items]
Total marketable securities	8,115	36,734
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total marketable securities	114,996	190,652
Cash
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	71,593	62,033
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	357,524	118,737
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	$ 69,882	$ 0

Cash, Cash Equivalents and Ma_4

Cash, Cash Equivalents and Marketable Securities - Schedule of Cash and Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	$ 498,999	$ 180,770
Cash and cash equivalents, fair value	498,999	180,770
Marketable securities, amortized cost	269,310	660,599
Marketable securities, unrealized gains	306	151
Marketable securities, unrealized losses	(23)	(449)
Marketable securities, fair value	269,593	660,301
Total cash, cash equivalents and marketable securities, amortized cost	768,318	841,369
Total cash, cash equivalents and marketable securities, unrealized gains	306	151
Total cash, cash equivalents and marketable securities, unrealized losses	(32)	(449)
Total cash, cash equivalents and marketable securities, fair value	768,592	841,071
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	19,799	17,461
Marketable securities, unrealized gains	4	1
Marketable securities, unrealized losses	(8)	0
Marketable securities, fair value	19,795	17,462
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	29,460	44,886
Marketable securities, unrealized gains	55	7
Marketable securities, unrealized losses	0	(14)
Marketable securities, fair value	29,515	44,879
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	97,071	370,498
Marketable securities, unrealized gains	102	143
Marketable securities, unrealized losses	(1)	(67)
Marketable securities, fair value	97,172	370,574
International government securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	8,109	36,810
Marketable securities, unrealized gains	6	0
Marketable securities, unrealized losses	0	(76)
Marketable securities, fair value	8,115	36,734
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	114,871	190,944
Marketable securities, unrealized gains	139	0
Marketable securities, unrealized losses	(14)	(292)
Marketable securities, fair value	114,996	190,652
Total cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	499,008	180,770
Cash and cash equivalents, unrealized gains	0	0
Cash and cash equivalents, unrealized losses	(9)	0
Cash and cash equivalents, fair value	498,999	180,770
Cash
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	71,593	62,033
Cash and cash equivalents, fair value	71,593	62,033
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	357,524	118,737
Cash and cash equivalents, fair value	357,524	118,737
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	69,891
Cash and cash equivalents, unrealized gains	0
Cash and cash equivalents, unrealized losses	(9)
Cash and cash equivalents, fair value	$ 69,882	$ 0

Cash, Cash Equivalents and Ma_5

Cash, Cash Equivalents and Marketable Securities - Schedule of Marketable Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Cash and Cash Equivalents [Abstract]
Due in one year	$ 190,344	$ 506,297
Due in one to two years	79,249	154,004
Total	$ 269,593	$ 660,301

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 498,999	$ 180,770
Marketable securities	269,593	660,301
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	357,524	118,737
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	69,882	0
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	427,406	118,737
Marketable securities	269,593	660,301
Strategic investments	28,814	12,334
Fair Value, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	19,795	17,462
Fair Value, Recurring | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	29,515	44,879
Fair Value, Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	97,172	370,574
Fair Value, Recurring | International government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	8,115	36,734
Fair Value, Recurring | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	114,996	190,652
Fair Value, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	357,524	118,737
Fair Value, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	69,882
Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	357,524	118,737
Marketable securities	0	0
Strategic investments	0	0
Fair Value, Recurring | Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 1 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 1 | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 1 | International government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 1 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	357,524	118,737
Fair Value, Recurring | Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	69,882	0
Marketable securities	269,593	660,301
Strategic investments	0	0
Fair Value, Recurring | Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	19,795	17,462
Fair Value, Recurring | Level 2 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	29,515	44,879
Fair Value, Recurring | Level 2 | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	97,172	370,574
Fair Value, Recurring | Level 2 | International government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	8,115	36,734
Fair Value, Recurring | Level 2 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	114,996	190,652
Fair Value, Recurring | Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Fair Value, Recurring | Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	69,882
Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Marketable securities	0	0
Strategic investments	28,814	12,334
Fair Value, Recurring | Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 3 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 3 | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 3 | International government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 3 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Recurring | Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	$ 0
Fair Value, Recurring | Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 0

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Level 3 Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 12,334	$ 7,623
Purchases	14,132	2,276
Proceeds from liquidation	(3,251)	(1,266)
Realized gains (losses)	2,285	(131)
Unrealized gains relating to investments still held at reporting date	3,314	3,832
Balance at end of period	$ 28,814	$ 12,334

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment by Category (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 143,923	$ 118,490
Less: accumulated depreciation and amortization	(41,583)	(30,131)
Property and equipment, net	102,340	88,359
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,183	2,222
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	27,384	19,693
Capitalized internal-use software costs
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,241	4,241
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	98,770	86,258
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 10,345	$ 6,076

Property and Equipment, Net - N

Property and Equipment, Net - Narrative (Details) - USD ($)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 23,000,000	$ 15,000,000	$ 13,800,000
Amount of internal-use software capitalized	0	800,000	50,000
Amortization expense of capitalized internal-use software	500,000	300,000	$ 1,200,000
Net carrying value of capitalized internal-use software	$ 400,000	$ 900,000

Operating Leases - Narrative (D

Operating Leases - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Oct. 31, 2019	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Leases [Abstract]
Rent expense, net of sublease income	$ 26,300		$ 27,700	$ 17,500
Operating lease costs		$ 11,700
Variable lease costs		1,700
Short-term lease costs		700
Lessee, Lease, Description [Line Items]
Commitments for operating leases that have not yet commenced		$ 189,826
Minimum
Lessee, Lease, Description [Line Items]
Operating leases that have not yet commenced, term of lease		10 years 3 months 18 days
Maximum
Lessee, Lease, Description [Line Items]
Operating leases that have not yet commenced, term of lease		12 years

Operating Leases - Schedule of

Operating Leases - Schedule of Operating Lease Costs (Details) $ in Thousands	3 Months Ended
	Jan. 31, 2020USD ($)
Leases [Abstract]
Operating cash flows used for operating leases	$ 9,495
Operating lease liabilities arising from obtaining ROU assets	$ 4,832
Weighted average remaining terms	8 years 3 months 18 days
Weighted average discount rate	5.20%

Operating Leases - Schedule o_2

Operating Leases - Schedule of Maturities of Operating Lease Liabilities (Details) $ in Thousands	Jan. 31, 2020USD ($)
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2021	$ 37,633
2022	50,472
2023	51,276
2024	49,723
2025	52,373
Thereafter	254,256
Gross lease payments	495,733
Less: Imputed interest	(64,683)
Less: Tenant improvement receivables	(14,381)
Less: Leases executed but not yet commenced	(189,826)
Present value of lease liabilities	$ 226,843

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2018	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Business Acquisition [Line Items]
Intangible assets acquired			$ 16,998
Goodwill		$ 48,598	48,598	$ 8,653
Other Business and Asset Acquisitions
Business Acquisition [Line Items]
Total consideration transferred under asset acquisition			14,500
Liabilities incurred as part of acquisition			5,300
Intangible assets acquired			11,700
Goodwill			2,200
Service agreements acquired			600
Asset Acquisitions
Business Acquisition [Line Items]
Intangible assets acquired			9,900
Service agreements acquired			$ 600
Term of services agreement			2 years
Shares sold in asset acquisition (in shares)			896,057
Cash consideration received in asset acquisition			$ 10,000
Premium recognized to reduce acquisition price			3,900
Astro Technology Inc.
Business Acquisition [Line Items]
Purchase price	$ 43,300
Expenses recognized outside of business combination		$ 3,700	1,600
Other acquisition related costs			400
Goodwill			$ 37,795
Unvested Securities in Return for Future Services | Astro Technology Inc.
Business Acquisition [Line Items]
Additional consideration transferred	$ 10,700

Acquisitions - Schedule of Allo

Acquisitions - Schedule of Allocation of Purchase Price (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 48,598	$ 48,598	$ 8,653
Astro Technology Inc.
Business Acquisition [Line Items]
Identified intangible asset - developed technology		5,300
Goodwill		37,795
Net tangible assets acquired		234
Total purchase price		$ 43,329

Acquisitions - Schedule of Inta

Acquisitions - Schedule of Intangible Assets Acquired (Details) $ in Thousands	12 Months Ended
	Jan. 31, 2019USD ($)
Business Acquisition [Line Items]
Amount of intangible assets acquired	$ 16,998
Weighted Average Life	5 years
Customer relationships
Business Acquisition [Line Items]
Amount of intangible assets acquired	$ 9,100
Weighted Average Life	7 years
Developed technology
Business Acquisition [Line Items]
Amount of intangible assets acquired	$ 6,700
Weighted Average Life	3 years
Assembled workforce
Business Acquisition [Line Items]
Amount of intangible assets acquired	$ 1,198
Weighted Average Life	2 years

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets, Net - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Goodwill [Roll Forward]
Balance at beginning of year	$ 48,598	$ 8,653
Additions due to acquisitions	0	39,945
Balance at end of year	$ 48,598	$ 48,598

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets, Net - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 21,325	$ 18,825
Accumulated amortization	7,795	3,622
Net carrying amount	13,530	15,203
Amortization expense of intangible assets	4,200	1,800	$ 500
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	9,100	9,100
Accumulated amortization	2,004	704
Net carrying amount	7,096	8,396
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	8,527	8,527
Accumulated amortization	4,976	2,743
Net carrying amount	3,551	5,784
Patents
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	2,500
Accumulated amortization	42
Net carrying amount	2,458
Assembled workforce
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,198	1,198
Accumulated amortization	773	175
Net carrying amount	$ 425	$ 1,023
Weighted Average | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period	5 years 6 months	6 years 6 months
Weighted Average | Developed technology
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period	1 year 7 months 6 days	2 years 7 months 6 days
Weighted Average | Patents
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period	4 years 10 months 24 days
Weighted Average | Assembled workforce
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period	8 months 12 days	1 year 8 months 12 days

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets, Net - Schedule of Expected Amortization Expense (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2021	$ 4,458
2022	3,118
2023	1,800
2024	1,800
2025	1,758
Thereafter	596
Net carrying amount	$ 13,530	$ 15,203

Revolving Credit Facility - Nar

Revolving Credit Facility - Narrative (Details) - USD ($)	May 30, 2019	Jan. 31, 2020
Line of Credit Facility [Line Items]
Letters of credit amount outstanding		$ 38,500,000
Line of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 215,000,000
Potential increase in limit of aggregate commitments	$ 200,000,000
Potential increase in limit of aggregate commitments, as a percentage of adjusted EBITDA	100.00%
Commitment fee percentage	0.10%
Annual fee percentage	1.25%
Fronting fee percentage	0.125%
Letter of credit amount issued		0
Letters of credit amount outstanding		0
Remaining borrowing capacity		$ 215,000,000
Line of Credit | Prime Rate | Revolving Credit Facility
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.25%
Line of Credit | LIBOR | Revolving Credit Facility
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	1 Months Ended
	Sep. 30, 2019lawsuit	Apr. 30, 2018USD ($)	Jan. 31, 2020USD ($)
Long-term Purchase Commitment [Line Items]
Letters of credit amount outstanding			$ 38,500,000
Number of class action lawsuits filed against the company | lawsuit	7
Hosting Commitments
Long-term Purchase Commitment [Line Items]
Minimum annual commitment amount under hosting commitments		$ 50,000,000
Total minimum commitment amount under hosting commitments		$ 250,000,000
Remaining minimum payment obligation			$ 162,500,000

Stockholders Equity - Narrative

Stockholders Equity - Narrative (Details)	Jun. 20, 2019USD ($)	Jun. 06, 2019shares	Dec. 31, 2017$ / sharesshares	Nov. 30, 2017USD ($)$ / sharesshares	Jun. 30, 2017$ / sharesshares	Apr. 30, 2017$ / shares	Jun. 30, 2017shares	Jan. 31, 2018USD ($)$ / shares	Jan. 31, 2020USD ($)voteplan$ / sharesshares	Jan. 31, 2019USD ($)$ / sharesshares	Jan. 31, 2018USD ($)$ / sharesshares	Jun. 07, 2019shares
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)									100,000,000
Number of equity incentive plans | plan									2
Number of shares reserved for future issuance (in shares)									118,291,000
Grant-date fair value of stock options granted | $									$ 21,400,000	$ 0	$ 100,000
Intrinsic value of stock options exercised | $									393,300,000	30,000,000	13,600,000
Unrecognized stock based compensation expense related to options | $									16,700,000
Payments for repurchase of stock | $									$ 0	$ 0	$ 40,506,000
Number of stock options granted (in shares)									3,663,000	0
Stock options
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)									8,425,000
Unrecognized stock based compensation expense, weighted average period of recognition									4 years 9 months 18 days
Fair value of common stock (in dollars per share) | $ / shares								$ 4.24			$ 4.24
Dividend yield									0.00%		0.00%
Restricted stock units
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)									42,002,000
Unrecognized stock based compensation expense, weighted average period of recognition									1 year 6 months
Weighted-average estimated fair value of shares granted (in dollars per share) | $ / shares									$ 18.93	$ 7.02	$ 4.15
Number of shares granted (in shares)									23,804,000
Unrecognized stock based compensation expense | $									$ 313,600,000
Compensation expense | $	$ 245,100,000
Restricted stock awards
Class of Stock [Line Items]
Unrecognized stock based compensation expense, weighted average period of recognition									3 years 8 months 12 days
Weighted-average estimated fair value of shares granted (in dollars per share) | $ / shares									$ 13.60	$ 7.86
Number of shares granted (in shares)									505,000		0
Unrecognized stock based compensation expense | $									$ 13,500,000
Employee stock purchase plan
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)									8,664,000
Stock purchase offering period									6 months
Dividend yield									0.00%
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)									5,000,000,000	660,000,000		5,000,000,000
Common stock, number of votes per share | vote									1
Number of shares issued under employee stock purchase plan (in shares)									300,000
Class B Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)									700,000,000	650,000,000		700,000,000
Common stock, number of votes per share | vote									10
Convertible Preferred Stock
Class of Stock [Line Items]
Conversion of convertible preferred stock to common stock in connection with direct listing (in shares)		373,400,000
Convertible preferred stock, shares authorized (in shares)									0	390,589,000
2019 Stock Option and Incentive Plan | Class A Common Stock
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)												60,200,000
Potential increase in number of shares authorized, as a percentage of total common stock outstanding									5.00%
2019 Employee Stock Purchase Plan | Class A Common Stock | Employee stock purchase plan
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)		9,000,000
Potential increase in number of shares authorized, as a percentage of total common stock outstanding		1.00%
Unrecognized stock based compensation expense, weighted average period of recognition									2 months 12 days
Unrecognized stock based compensation expense | $									$ 1,700,000
Potential increase in number of shares authorized (in shares)		6,000,000
Percentage of discount on market price for eligible employees		15.00%
Purchase price of common stock, percentage of fair market value		85.00%
Tender Offer
Class of Stock [Line Items]
Sale of stock (in shares)				17,900,000
Sale price of stock (in dollars per share) | $ / shares				$ 8.37
Discount on sale of stock				10.00%
Gross sale price of stock | $				$ 150,000,000
Shares from Company Co-Founder | Class B Common Stock
Class of Stock [Line Items]
Shares repurchased (in shares)				800,000
Price of shares repurchased (in dollars per share) | $ / shares				$ 8.37
Payments for repurchase of stock | $				$ 6,600,000
Fair value of common stock (in dollars per share) | $ / shares				$ 4.24
Compensation expense | $				$ 38,900,000
Deemed dividends recorded as a reduction to stockholders' deficit | $				$ 40,900,000
Shares from Former Employees | Class B Common Stock
Class of Stock [Line Items]
Number of shares repurchased (in shares)					100,000
Shares repurchased (in shares)							100,000
Price of shares repurchased (in dollars per share) | $ / shares					$ 7.41	$ 7.41
Shares from Current and Former Employees | Class B Common Stock
Class of Stock [Line Items]
Shares repurchased (in shares)			100,000
Price of shares repurchased (in dollars per share) | $ / shares			$ 8.37
Compensation expense | $								$ 500,000

Stockholders Equity - Schedule

Stockholders Equity - Schedule of Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)	100,000,000
Series A
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		84,751,000
Convertible preferred stock, shares outstanding (in shares)		84,751,000
Net proceeds		$ 8,011
Convertible preferred stock, liquidation preference		$ 8,060
Series B
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		43,320,000
Convertible preferred stock, shares outstanding (in shares)		43,320,000
Net proceeds		$ 10,674
Convertible preferred stock, liquidation preference		$ 10,700
Series C
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		64,805,000
Convertible preferred stock, shares outstanding (in shares)		64,805,000
Net proceeds		$ 42,678
Convertible preferred stock, liquidation preference		$ 42,750
Series D
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		47,059,000
Convertible preferred stock, shares outstanding (in shares)		42,490,000
Net proceeds		$ 108,266
Convertible preferred stock, liquidation preference		$ 108,350
Series D-1
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		1,235,000
Convertible preferred stock, shares outstanding (in shares)		1,235,000
Net proceeds		$ 2,561
Convertible preferred stock, liquidation preference		$ 3,149
Series E
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		26,787,000
Convertible preferred stock, shares outstanding (in shares)		22,602,000
Net proceeds		$ 134,832
Convertible preferred stock, liquidation preference		$ 135,000
Series E-1
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		6,047,000
Convertible preferred stock, shares outstanding (in shares)		6,047,000
Net proceeds		$ 37,940
Convertible preferred stock, liquidation preference		$ 37,950
Series F
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		19,867,000
Convertible preferred stock, shares outstanding (in shares)		19,867,000
Net proceeds		$ 154,957
Convertible preferred stock, liquidation preference		$ 155,000
Series F-1
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		6,793,000
Convertible preferred stock, shares outstanding (in shares)		6,793,000
Net proceeds		$ 52,940
Convertible preferred stock, liquidation preference		$ 53,000
Series G
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		24,718,000
Convertible preferred stock, shares outstanding (in shares)		24,718,000
Net proceeds		$ 229,648
Convertible preferred stock, liquidation preference		$ 230,000
Series G-1
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		2,149,000
Convertible preferred stock, shares outstanding (in shares)		2,149,000
Net proceeds		$ 20,000
Convertible preferred stock, liquidation preference		$ 20,000
Series G-2
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		17,241,000
Convertible preferred stock, shares outstanding (in shares)		17,241,000
Net proceeds		$ 150,000
Convertible preferred stock, liquidation preference		$ 150,000
Series G-3
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		1,465,000
Convertible preferred stock, shares outstanding (in shares)		1,465,000
Net proceeds		$ 12,714
Convertible preferred stock, liquidation preference		$ 8,700
Series H
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		35,150,000
Convertible preferred stock, shares outstanding (in shares)		33,470,000
Net proceeds		$ 398,082
Convertible preferred stock, liquidation preference		$ 398,468
Series H-1
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)		9,202,000
Convertible preferred stock, shares outstanding (in shares)		2,419,000
Net proceeds		$ 28,798
Convertible preferred stock, liquidation preference		$ 28,798
Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares authorized (in shares)	0	390,589,000
Convertible preferred stock, shares outstanding (in shares)	0	373,372,000
Net proceeds		$ 1,392,101
Convertible preferred stock, liquidation preference	$ 0	$ 1,389,925

Stockholders Equity - Common St

Stockholders Equity - Common Stock Reserved for Future Issuance (Details) shares in Thousands	Jan. 31, 2020shares
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)	118,291
Shares available for future grants
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)	59,200
Stock options
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)	8,425
Restricted stock units outstanding
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)	42,002
Shares available for ESPP
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)	8,664

Stockholders Equity - Schedul_2

Stockholders Equity - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Number of stock options outstanding
Outstanding at beginning of period (in shares)	18,406,000
Granted (in shares)	3,663,000	0
Exercised (in shares)	(13,268,000)
Canceled (in shares)	(376,000)
Outstanding at end of period (in shares)	8,425,000	18,406,000
Stock options vested and exercisable at end of period, number of shares (in shares)	5,342,000
Stock options vested and expected to vest at end of period, number of shares (in shares)	8,425,000
Weighted-average exercise price per share
Outstanding at beginning of period (in dollars per share)	$ 0.94
Granted (in dollars per share)	10.58
Exercised (in dollars per share)	1.04
Canceled (in dollars per share)	7.67
Outstanding at end of period (in dollars per share)	4.68	$ 0.94
Stock options vested and exercisable at end of period, weighted-average exercise price per share (in dollars per share)	1.44
Stock options vested and expected to vest at end of period, weighted-average exercise price per share (in dollars per share)	$ 4.68
Weighted-average remaining contractual term (In years)
Outstanding, weighted-average remaining contractual term	6 years 3 months 7 days	6 years 1 month 13 days
Stock options vested and exercisable, weighted-average remaining contractual term	4 years 11 months 15 days
Stock options vested and expected to vest, weighted-average remaining contractual term	6 years 3 months 7 days
Aggregate intrinsic value
Outstanding, aggregate intrinsic value	$ 135,224	$ 177,012
Stock options vested and exercisable, aggregate intrinsic value	103,049
Stock options vested and expected to vest, aggregate intrinsic value	$ 135,224

Stockholders Equity - Schedul_3

Stockholders Equity - Schedule of Restricted Stock Units and Restricted Stock Awards (Details) - $ / shares	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Restricted stock units
Number of shares
Unvested at beginning of period (in shares)	63,114,000
Granted (in shares)	23,804,000
Released (in shares)	(40,318,000)
Canceled (in shares)	(4,598,000)
Unvested at end of period (in shares)	42,002,000	63,114,000
Weighted-average grant date fair value (per share)
Unvested at beginning of period (in dollars per share)	$ 4.87
Granted (in dollars per share)	18.93	$ 7.02	$ 4.15
Released (in dollars per share)	4.84
Canceled (in dollars per share)	8.45
Unvested at end of period (in dollars per share)	$ 12.48	$ 4.87
Restricted stock awards
Number of shares
Unvested at beginning of period (in shares)	2,289,000
Granted (in shares)	505,000		0
Released (in shares)	(1,205,000)
Canceled (in shares)	(10,000)
Unvested at end of period (in shares)	1,579,000	2,289,000
Weighted-average grant date fair value (per share)
Unvested at beginning of period (in dollars per share)	$ 7.23
Granted (in dollars per share)	13.60	$ 7.86
Released (in dollars per share)	7.74
Canceled (in dollars per share)	2.37
Unvested at end of period (in dollars per share)	$ 8.91	$ 7.23

Stockholders Equity - Schedul_4

Stockholders Equity - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Tender Offers and Repurchases
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 0	$ 0	$ 39,374
Tender Offers and Repurchases | Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	0	252
Tender Offers and Repurchases | Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	0	30,674
Tender Offers and Repurchases | Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	0	6,549
Tender Offers and Repurchases | General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	0	1,899
Stock Transfers
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	14,821	0
Stock Transfers | Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	533	0
Stock Transfers | Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	6,228	0
Stock Transfers | Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	1,707	0
Stock Transfers | General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	6,353	0
Excluding Tender Offers and Stock Transfers
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	426,524	8,311	8,709
Excluding Tender Offers and Stock Transfers | Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	16,013	199	239
Excluding Tender Offers and Stock Transfers | Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	226,507	3,720	4,586
Excluding Tender Offers and Stock Transfers | Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	98,797	970	1,495
Excluding Tender Offers and Stock Transfers | General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 85,207	$ 3,422	$ 2,389

Stockholders Equity - Schedul_5

Stockholders Equity - Schedule of Share-based Payment Award, Stock Options and ESPP, Valuation Assumptions (Details) - $ / shares	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2018
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		6 years 18 days
Expected volatility, min (as percent)	43.00%
Expected volatility, max (as percent)	44.00%
Expected volatility (as percent)		41.00%
Risk-free interest rate, min (as percent)	2.33%
Risk-free interest rate, max (as percent)	2.52%
Risk-free interest rate (as percent)		1.62%
Dividend yield	0.00%	0.00%
Fair value of common stock on grant date (in dollars per share)		$ 4.24
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, min (as percent)	40.00%
Expected volatility, max (as percent)	42.00%
Risk-free interest rate, min (as percent)	1.68%
Risk-free interest rate, max (as percent)	2.08%
Dividend yield	0.00%
Minimum | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days
Fair value of common stock on grant date (in dollars per share)	$ 11.67
Minimum | Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	3 months 18 days
Fair value of common stock on grant date (in dollars per share)	$ 23.82
Maximum | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 6 months
Fair value of common stock on grant date (in dollars per share)	$ 19.36
Maximum | Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 months
Fair value of common stock on grant date (in dollars per share)	$ 38.62

Other Income (Expense), Net (De

Other Income (Expense), Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Other Income and Expenses [Abstract]
Interest income, net	$ 16,190	$ 13,400	$ 3,838
Unrealized gains (losses) on foreign exchange	(786)	(869)	1,970
Transaction losses on foreign exchange	(1,526)	(99)	(1,503)
Change in fair value of strategic investments	5,599	3,701	27
Other non-operating income, net	1,033	13	249
Other income (expense), net	$ 20,510	$ 16,146	$ 4,581

Income Taxes - Schedule of Loss

Income Taxes - Schedule of Loss Before Income Taxes, Domestic and Foreign (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Income Tax Disclosure [Abstract]
United States	$ (294,259)	$ (85,175)	$ (100,364)
Foreign	(273,509)	(52,887)	(38,906)
Loss before income taxes	$ (567,768)	$ (138,062)	$ (139,270)

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Current:
Federal	$ 0	$ 0	$ 0
State	303	355	20
Foreign	1,919	279	894
Total current	2,222	634	914
Deferred:
Federal	(120)	(200)	0
State	(23)	(120)	0
Foreign	(1,490)	526	(121)
Total deferred	(1,633)	206	(121)
Provision for income taxes	$ 589	$ 840	$ 793

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Income Tax Disclosure [Abstract]
Tax at statutory federal rate	21.00%	21.00%	33.80%
State tax, net of federal benefit	12.68%	2.12%	2.19%
Stock-based compensation	45.16%	(2.95%)	(2.29%)
Credits	17.37%	6.01%	4.34%
Foreign rate differential	(7.06%)	9.52%	(9.92%)
Other	(1.49%)	(3.80%)	(0.55%)
Change in statutory tax rates	0.01%	0.13%	(17.93%)
Change in valuation allowance	(87.77%)	(32.64%)	(10.21%)
Effective tax rate	(0.10%)	(0.61%)	(0.57%)

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Deferred tax assets (liabilities):
Accrued liabilities	$ 10,646	$ 7,907	$ 3,905
Accounts receivable	93	70	131
Deferred rent		4,304	1,438
Operating lease liabilities	51,085
Operating lease right-of-use assets	(42,919)
Net operating losses	415,236	65,385	46,736
Tax credits	120,743	22,116	13,510
Intangible assets	13,176	15,258
Intangible assets			(108)
Property and equipment	2,566	870	1,637
Stock-based compensation	43,182	(2,549)	(275)
Other	(1,309)	(684)
Other			88
Total gross deferred tax assets	612,499	112,677	67,062
Valuation allowance	(611,027)	(112,693)	(66,557)
Total deferred tax assets (liabilities), net		$ (16)
Total deferred tax assets (liabilities), net	$ 1,472		$ 505

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Operating Loss Carryforwards [Line Items]
Increase in valuation allowance	$ 498,300,000	$ 46,100,000	$ 14,200,000
Unrecognized tax benefits	37,495,000	20,484,000	18,545,000	$ 17,767,000
Unrecognized tax benefits that would impact effective tax rate	0	$ 0	$ 0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	1,500,000,000
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	1,200,000,000
Capital Loss Carryforward | Federal
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0
Capital Loss Carryforward | State
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0
Research Tax Credit Carryforward | Federal
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	99,500,000
Research Tax Credit Carryforward | State
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 54,000,000

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 20,484	$ 18,545	$ 17,767
Increase related to prior year tax provisions	1	0	28
Decrease related to prior year tax provisions	(2,495)	(2,076)	(2,687)
Increase related to current year tax provisions	19,526	4,022	3,472
Lapse of statute of limitations	(21)	(7)	(35)
Balance at end of period	$ 37,495	$ 20,484	$ 18,545

Net Loss per Share Attributab_3

Net Loss per Share Attributable to Slack Common Stockholders - Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Numerator:
Net loss attributable to Slack	$ (571,058)	$ (140,683)	$ (140,085)
Less: Deemed dividends to preferred stockholders	0	0	40,883
Net loss attributable to Slack common stockholders	$ (571,058)	$ (140,683)	$ (180,968)
Denominator:
Weighted average common shares outstanding (in shares)	399,461	121,732	122,865
Net loss per share attributable to Slack common stockholders, basic and diluted (in dollars per share)	$ (1.43)	$ (1.16)	$ (1.47)

Net Loss per Share Attributab_4

Net Loss per Share Attributable to Slack Common Stockholders - Potentially Dilutive Securities Excluded from Diluted Per Share Calculations (Details) - shares shares in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	52,820	457,296	403,110
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	0	373,372	337,483
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	8,425	18,406	23,720
Unvested early exercised stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	0	115	419
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	42,002	63,114	40,594
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	1,579	2,289	894
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	814	0	0

Geographic Information (Details

Geographic Information (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total tangible long-lived assets	$ 300,170	$ 88,359
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total tangible long-lived assets	256,695	76,768
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total tangible long-lived assets	$ 43,475	$ 11,591

Defined Contribution Plan (Deta

Defined Contribution Plan (Details) - USD ($)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Retirement Benefits [Abstract]
Employer matching contribution, percent of match	50.00%
Maximum annual amount matched by employer	$ 4,000
Employer matching contribution, vesting period	1 year
Matching contributions made by employer	$ 5,800,000	$ 3,700,000	$ 2,200,000