Slack (WORK) 10-Q 4 Dec 19 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Oct. 31, 2019	Nov. 15, 2019
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Oct. 31, 2019
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 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 Central Index Key	0001764925
Current Fiscal Year End Date	--01-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Class A Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		291,362,103
Class B Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		259,018,136

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Oct. 31, 2019	Jan. 31, 2019
Current assets:
Cash and cash equivalents	$ 476,474	$ 180,770
Marketable securities	297,632	660,301
Accounts receivable, net	84,977	87,438
Prepaid expenses and other current assets	58,811	54,213
Total current assets	917,894	982,722
Restricted cash	38,490	20,490
Strategic investments	24,215	12,334
Property and equipment, net	109,806	88,359
Intangible assets, net	12,104	15,203
Goodwill	48,598	48,598
Other assets	33,745	31,250
Total assets	1,184,852	1,198,956
Current liabilities:
Accounts payable	11,159	16,613
Accrued compensation and benefits	47,029	46,151
Accrued expenses and other current liabilities	44,641	29,809
Deferred revenue	302,690	239,825
Total current liabilities	405,519	332,398
Deferred revenue, noncurrent	1,234	2,048
Other liabilities	30,868	22,904
Total liabilities	437,621	357,350
Commitments and contingencies (Note 6)
Stockholders’ equity:
Convertible preferred stock	0	1,392,101
Common stock	55	13
Additional paid-in-capital	1,879,601	105,633
Accumulated other comprehensive loss	13	(498)
Accumulated deficit	(1,147,618)	(665,563)
Total Slack Technologies, Inc. stockholders’ equity	732,051	831,686
Noncontrolling interest	15,180	9,920
Total stockholders’ equity	747,231	841,606
Total liabilities and stockholders’ equity	$ 1,184,852	$ 1,198,956

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Income Statement [Abstract]
Revenue	$ 168,725	$ 105,648	$ 448,519	$ 278,585
Cost of revenue	23,140	13,540	72,820	35,002
Gross profit	145,585	92,108	375,699	243,583
Operating expenses:
Research and development	94,853	40,990	363,725	111,582
Sales and marketing	96,210	67,687	299,440	163,408
General and administrative	49,524	34,185	209,624	79,361
Total operating expenses	240,587	142,862	872,789	354,351
Loss from operations	(95,002)	(50,754)	(497,090)	(110,768)
Other income (expense), net	7,135	3,376	17,323	7,263
Loss before income taxes	(87,867)	(47,378)	(479,767)	(103,505)
Provision (benefit) for income taxes	(101)	318	(504)	753
Net loss	(87,766)	(47,696)	(479,263)	(104,258)
Net income (loss) attributable to noncontrolling interest	1,395	(24)	2,792	156
Net loss attributable to Slack	$ (89,161)	$ (47,672)	$ (482,055)	$ (104,414)
Basic and diluted net loss per share:
Net loss per share attributable to Slack common stockholders, basic and diluted (in dollars per share)	$ (0.16)	$ (0.39)	$ (1.38)	$ (0.86)
Weighted-average shares used in computing net loss per share attributable to Slack common stockholders, basic and diluted (in shares)	544,057	122,880	348,580	120,924

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (87,766)	$ (47,696)	$ (479,263)	$ (104,258)
Other comprehensive income (loss), net of tax:
Change in unrealized income or loss on marketable securities	132	(246)	511	(465)
Other comprehensive income (loss), net of tax	132	(246)	511	(465)
Comprehensive loss	(87,634)	(47,942)	(478,752)	(104,723)
Comprehensive income (loss) attributable to noncontrolling interest	1,395	(24)	2,792	156
Comprehensive loss attributable to Slack	$ (89,029)	$ (47,918)	$ (481,544)	$ (104,879)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In-Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Noncontrolling Interest	Restricted stock awardsCommon Stock	Restricted stock units	Restricted stock unitsCommon Stock	Restricted stock unitsAdditional Paid-In-Capital	Series H Preferred Stock	Series H Preferred StockConvertible Preferred Stock	Series H-1 Preferred Stock	Series H-1 Preferred StockConvertible Preferred Stock
Beginning of period (in shares) at Jan. 31, 2018		337,483	119,735
Beginning 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)			1,163
Exercise of stock options	832			832
Vesting of early exercised stock options	101			101
Cancellation of restricted stock awards (RSAs) (in shares)								(19)
Repurchase of early exercised stock options (in shares)			(103)
Other comprehensive income (loss)	(516)				(516)
Stock-based compensation	6,118			6,118
Net income (loss)	(24,876)					(24,882)	6
End of period (in shares) at Apr. 30, 2018		337,483	120,776
End of period at Apr. 30, 2018	500,947	$ 965,221	$ 12	78,936	(1,605)	(549,762)	8,145
Beginning of period (in shares) at Jan. 31, 2018		337,483	119,735
Beginning 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]
Vesting of early exercised stock options	194
Other comprehensive income (loss)	(465)
Net income (loss)	(104,258)
End of period (in shares) at Oct. 31, 2018		373,372	125,891
End of period at Oct. 31, 2018	868,764	$ 1,392,101	$ 12	99,204	(1,554)	(629,294)	8,295
Beginning of period (in shares) at Apr. 30, 2018		337,483	120,776
Beginning of period at Apr. 30, 2018	500,947	$ 965,221	$ 12	78,936	(1,605)	(549,762)	8,145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			1,466
Exercise of stock options	1,077			1,077
Vesting of early exercised stock options	93			93
Issuance of restricted stock awards (in shares)								119
Issuance of stock (in shares)			900
Issuance of stock	6,084			6,084
Other comprehensive income (loss)	297				297
Stock-based compensation	1,638			1,638
Net income (loss)	(31,686)					(31,860)	174
End of period (in shares) at Jul. 31, 2018		337,483	123,261
End of period at Jul. 31, 2018	478,450	$ 965,221	$ 12	87,828	(1,308)	(581,622)	8,319
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			923
Exercise of stock options	771			771
Vesting of early exercised stock options	90			90
Issuance of restricted stock awards (in shares)			1,721
Repurchase of early exercised stock options (in shares)			(14)
Issuance of stock (in shares)													33,470		2,419
Issuance of stock												$ 398,082	$ 398,082	$ 28,798	$ 28,798
Other comprehensive income (loss)	(246)				(246)
Stock-based compensation	10,515			10,515
Net income (loss)	(47,696)					(47,672)	(24)
End of period (in shares) at Oct. 31, 2018		373,372	125,891
End of period at Oct. 31, 2018	868,764	$ 1,392,101	$ 12	99,204	(1,554)	(629,294)	8,295
Beginning of period (in shares) at Jan. 31, 2019		373,372	127,573
Beginning 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)			2,694
Exercise of stock options	2,907			2,907
Vesting of early exercised stock options	88			88
Issuance of restricted stock awards (in shares)								505
Other comprehensive income (loss)	420				420
Stock-based compensation	3,639			3,639
Net income (loss)	(31,881)					(33,332)	1,451
End of period (in shares) at Apr. 30, 2019		373,372	130,772
End of period at Apr. 30, 2019	816,779	$ 1,392,101	$ 13	112,267	(78)	(698,895)	11,371
Beginning of period (in shares) at Jan. 31, 2019		373,372	127,573
Beginning 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)	11,636
Vesting of early exercised stock options	$ 214
Other comprehensive income (loss)	511
Net income (loss)	(479,263)
End of period (in shares) at Oct. 31, 2019		0	549,015
End of period at Oct. 31, 2019	747,231	$ 0	$ 55	1,879,601	13	(1,147,618)	15,180
Beginning of period (in shares) at Apr. 30, 2019		373,372	130,772
Beginning of period at Apr. 30, 2019	816,779	$ 1,392,101	$ 13	112,267	(78)	(698,895)	11,371
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			8,046
Exercise of stock options	6,805		$ 1	6,804
Vesting of early exercised stock options	69			69
Cancellation of restricted stock awards (RSAs) (in shares)			(10)
Repurchase of early exercised stock options (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)	$ 37	1,392,064
Issuance of stock (in shares)										30,388
Issuance of common stock upon settlement of restricted stock units (RSUs)									$ 0	$ 3	$ (3)
Other comprehensive income (loss)	(41)				(41)
Stock-based compensation	285,787			285,787
Net income (loss)	(359,616)					(359,562)	(54)
End of period (in shares) at Jul. 31, 2019		0	542,566
End of period at Jul. 31, 2019	749,783	$ 0	$ 54	1,796,988	(119)	(1,058,457)	11,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			896
Exercise of stock options	1,345		$ 0	1,345
Vesting of early exercised stock options	57			57
Issuance of stock (in shares)										5,217
Issuance of common stock upon settlement of restricted stock units (RSUs)									$ 0	$ 1	$ (1)
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)	132				132
Stock-based compensation	73,861			73,861
Net income (loss)	(87,766)					(89,161)	1,395
End of period (in shares) at Oct. 31, 2019		0	549,015
End of period at Oct. 31, 2019	$ 747,231	$ 0	$ 55	$ 1,879,601	$ 13	$ (1,147,618)	$ 15,180

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018
Cash flows from operating activities:
Net loss	$ (479,263)	$ (104,258)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	20,419	11,227
Loss on disposal of property and equipment	0	2,165
Stock-based compensation	363,287	18,271
Amortization of deferred contract acquisition costs	5,522	1,965
Net amortization of bond premium on debt securities available for sale	(2,077)	(1,589)
Change in fair value of strategic investments	(5,791)	(287)
Other non-cash charges	(742)	500
Changes in operating assets and liabilities:
Accounts receivable	2,920	(12,315)
Prepaid expenses and other assets	(12,049)	(38,053)
Accounts payable	1,005	9,251
Accrued compensation and benefits	879	7,488
Deferred revenue	62,051	64,719
Other current and long-term liabilities	20,935	17,462
Net cash used in operating activities	(22,904)	(23,454)
Cash flows from investing activities:
Purchases of marketable securities	(202,895)	(734,778)
Maturities of marketable securities	402,255	479,291
Sales of marketable securities	166,074	11,271
Acquisitions of businesses, net of cash acquired	0	(45,313)
Acquisition of intangible assets	0	(2,382)
Purchases of property and equipment	(38,276)	(42,704)
Sales of property and equipment	0	762
Capitalized software development costs	0	(415)
Purchase of strategic investments	(9,283)	(1,610)
Proceeds from liquidation of strategic investments	2,858	190
Net cash provided by (used in) investing activities	320,733	(335,688)
Cash flows from financing activities:
Proceeds from exercise of stock options	11,612	2,637
Payment of contingent consideration for an acquisition	(5,000)	0
Issuance of common stock for employee stock purchase plan	7,351	0
Net proceeds from issuance of convertible preferred stock	0	426,880
Capital contributions from noncontrolling interest holders	3,840	0
Distributions to noncontrolling interest holders	(1,372)	0
Issuance of common stock to third party	0	6,084
Other financing activities	(556)	(47)
Net cash provided by financing activities	15,875	435,554
Net increase in cash, cash equivalents and restricted cash	313,704	76,412
Cash, cash equivalents and restricted cash at beginning of period	201,260	138,063
Cash, cash equivalents and restricted cash at end of period	514,964	214,475
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,157	298
Non-cash investing and financing activities:
Increase in purchases of property and equipment included in liabilities	491	770
Vesting of early exercised stock options	214	194
Unrealized short-term gain on marketable securities	$ 686	$ 219

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	9 Months Ended
	Oct. 31, 2019
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. 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 $0 and $30.4 million in general and administrative expense for the three and nine months ended October 31, 2019 , respectively. 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. Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”), regarding interim financial reporting. The accompanying condensed consolidated financial statements 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 condensed 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. The unaudited condensed consolidated balance sheet as of January 31, 2019 included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including certain notes required by U.S. GAAP on an annual reporting basis. In management's opinion, the unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the balance sheets, statements of comprehensive loss, statements of stockholders’ equity, and statements of cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full fiscal year or any future period. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Company’s final prospectus filed with the SEC pursuant to Rule 424(b) under the Securities Act of 1933, as amended, on June 20, 2019 , and as amended by the prospectus supplement dated September 5, 2019 (the “Prospectus”). Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the condensed 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. Summary of Significant Accounting Policies The Company’s significant accounting policies are discussed in “Index to Consolidated Financial Statements–Note 1. Description of Business and Summary of Significant Accounting Policies” in the Notes to Consolidated Financial Statements in its Prospectus. There have been no significant changes to these policies during the three months ended October 31, 2019 . Recently Issued Accounting Standards Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases , which supersedes the guidance in topic ASC 840, Leases. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. Under the standard, disclosures are required to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The Company will be required to recognize and measure leases existing at, or entered into after, the beginning of the earliest comparative period presented using a modified retrospective approach, with certain practical expedients available. For public companies, Topic 842 is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The Company has elected to use the extended transition period that allows the Company to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are made applicable to private companies under the Jumpstart Our Business Startups Act. For as long as the Company remains an “emerging growth company,” the new guidance is effective for annual reporting periods beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020, and is required to be applied using a modified retrospective approach. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of this standard and currently believes the most significant impact upon adoption will be the recognition of material right-of-use assets and lease liabilities on its condensed consolidated balance sheets associated with operating leases. The Company does not believe this standard will have a material impact on its condensed consolidated statements of operations. 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 is currently evaluating the impact of the adoption of this standard on its condensed 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 fiscal years 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 condensed 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, and interim periods within those years, beginning after December 15, 2019, 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 condensed consolidated financial statements.

Revenue and Contract Costs

Revenue and Contract Costs	9 Months Ended
	Oct. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue and Contract Costs	Revenue and Contract Costs Contract Balances Contract liabilities consist of deferred revenue. The Company recognized $116.0 million and $66.9 million during the three months ended October 31, 2019 and 2018 , respectively, that was included in deferred revenue balances at the beginning of the respective periods. The Company recognized $195.7 million and $103.0 million during the nine months ended October 31, 2019 and 2018 , respectively, that was included in deferred revenue balances at the beginning of the respective periods. Contract Costs, Net Sales commissions earned by the Company’s sales force are capitalized as deferred costs within prepaid expenses and other current assets and other assets in the accompanying condensed consolidated balance sheets. Deferred commissions, net, included in prepaid expenses and other current assets were $9.6 million and $5.3 million as of October 31, 2019 and January 31, 2019 , respectively. Deferred commissions, net, included in other assets were $19.2 million and $11.9 million as of October 31, 2019 and January 31, 2019 , respectively. Amortized costs are included in sales and marketing expense in the accompanying condensed consolidated statements of operations and were $2.2 million and $0.9 million for the three months ended October 31, 2019 and 2018 , respectively, and $5.5 million and $2.0 million for the nine months ended October 31, 2019 and 2018 , respectively. There was no impairment loss in relation to the deferred costs for any period presented. Remaining Performance Obligation As of October 31, 2019 , future estimated revenue related to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period was $279.3 million , of which 55% , 36% , 7% , 1% , and 1% is expected to be recognized in the twelve months ending October 31, 2020, 2021, 2022, 2023, and 2024, respectively. 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. 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): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 United States $ 105,775 $ 67,345 $ 280,838 $ 177,923 International 62,950 38,303 167,681 100,662 Total $ 168,725 $ 105,648 $ 448,519 $ 278,585 No individual foreign country contributed in excess of 10% of revenue for the three months or nine months ended October 31, 2019 and 2018 .

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Oct. 31, 2019
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, certificates of deposit, 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 condensed 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 October 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 327,471 $ — $ — $ 327,471 Commercial paper — 88,814 — 88,814 Total cash equivalents $ 327,471 $ 88,814 $ — $ 416,285 Marketable securities: Commercial paper $ — $ 37,369 $ — $ 37,369 U.S. agency securities — 13,995 — 13,995 U.S. government securities — 110,008 — 110,008 International government securities — 20,327 — 20,327 Corporate bonds — 115,933 — 115,933 Total marketable securities $ — $ 297,632 $ — $ 297,632 Noncurrent assets: Strategic investments $ — $ — $ 24,215 $ 24,215 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): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 Balance at beginning of period $ 17,496 $ 8,738 $ 12,334 $ 7,623 Purchases 3,813 710 9,283 1,610 Proceeds from liquidation — (37 ) (3,193 ) (171 ) Realized gains (losses) (466 ) (363 ) 2,227 (429 ) Unrealized gains relating to investments still held at reporting date 3,372 301 3,564 716 Balance at end of period $ 24,215 $ 9,349 $ 24,215 $ 9,349

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Oct. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	Balance Sheet Components Cash, Cash Equivalents, and Marketable Securities The following tables summarize the amortized cost, unrealized gains and losses, and estimated fair value of cash, cash equivalents, and marketable securities consisting of the following (in thousands): As of October 31, 2019 Amortized Unrealized Unrealized Fair value Cash and cash equivalents: Cash $ 60,189 $ — $ — $ 60,189 Money market funds 327,471 — — 327,471 Commercial paper 88,819 5 (10 ) 88,814 Total cash and cash equivalents 476,479 5 (10 ) 476,474 Marketable securities: Commercial paper $ 37,365 $ 7 $ (3 ) $ 37,369 U.S. agency securities 13,981 19 (6 ) 13,994 U.S. government securities 109,777 231 — 110,008 International government securities 20,313 15 — 20,328 Corporate bonds 115,807 138 (12 ) 115,933 Total marketable securities 297,243 410 (21 ) 297,632 Total cash, cash equivalents and marketable securities $ 773,722 $ 415 $ (31 ) $ 774,106 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 were immaterial as of October 31, 2019 and January 31, 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 October 31, 2019 or January 31, 2019 to represent an other-than temporary impairment or credit losses. The following table classifies marketable securities by contractual maturities (in thousands): As of October 31, 2019 January 31, 2019 Due in one year $ 242,512 $ 506,297 Due in one to two years 55,120 154,004 Total $ 297,632 $ 660,301 Property and Equipment, Net The following is a summary of the Company’s property and equipment by category (in thousands): As of October 31, 2019 January 31, 2019 Leasehold improvements $ 92,917 $ 86,258 Furniture and fixtures 26,229 19,693 Capitalized internal-use software costs 4,241 4,241 Computer equipment 3,093 2,222 Construction in progress 19,331 6,076 Property and equipment, gross 145,811 118,490 Less: accumulated depreciation and amortization (36,005 ) (30,131 ) Property and equipment, net $ 109,806 $ 88,359 As of October 31, 2019 and January 31, 2019 , property and equipment, net attributed to United States were 83% and 87% , respectively, of total property and equipment, net. There was no individual foreign country with an excess of 10% of total property and equipment, net as of October 31, 2019 or January 31, 2019 . Depreciation and amortization expense was $6.7 million and $3.9 million for the three months ended October 31, 2019 and 2018 , respectively. Depreciation and amortization expense was $17.3 million and $10.5 million for the nine months ended October 31, 2019 and 2018 , respectively. Intangible Assets, Net Intangible assets consist of the following (in thousands): October 31, 2019 Weighted-average Gross carrying Accumulated Net carrying Customer relationships 5.7 years $ 9,100 $ 1,679 $ 7,421 Developed technology 1.8 years 8,527 4,418 4,109 Assembled workforce 1.0 year 1,198 624 574 Total $ 18,825 $ 6,721 $ 12,104 January 31, 2019 Weighted-average Gross carrying Accumulated Net carrying 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 Amortization expense of intangible assets was $1.0 million and $0.7 million for the three months ended October 31, 2019 and 2018 , respectively. Amortization expense of intangible assets was $3.1 million and $0.8 million for the nine months ended October 31, 2019 and 2018 , respectively. As of October 31, 2019 , expected amortization expense relating to intangible assets for each of the next five fiscal years and thereafter is as follows (in thousands): Year ending January 31, 2020 (3 months remaining) $ 1,033 2021 3,957 2022 2,618 2023 1,300 2024 1,300 Thereafter 1,896 Total $ 12,104

Revolving Credit Facility

Revolving Credit Facility	9 Months Ended
	Oct. 31, 2019
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 October 31, 2019 , 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 October 31, 2019 .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Oct. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Lease Commitments The Company has entered into various noncancelable operating leases for its facilities expiring between fiscal years 2020 and 2031. Certain operating leases contain provisions under which monthly rent escalates over time. When lease agreements contain escalating rent clauses or free rent periods, the Company recognizes rent expense on a straight-line basis over the term of the lease. In March 2019 , the Company entered into a noncancelable operating lease for an office facility in San Francisco, California. In connection with entering into the lease agreement, the Company made a security deposit of $18.0 million in the form of a standby letter of credit, which is included in restricted cash as of October 31, 2019 . The lease term is from March 2019 through June 2030 , with future minimum lease payments of $165.8 million . The Company is entitled to receive tenant improvement reimbursements not to exceed $25.4 million . In September 2019, the Company entered into an amendment that would provide an additional free rent period in the event the Company’s access to certain floors is delayed. Rent expense, net of sublease income, was $9.3 million and $7.6 million for the three months ended October 31, 2019 and 2018 , respectively. Rent expense, net of sublease income, was $26.3 million and $19.6 million for the nine months ended October 31, 2019 and 2018 , respectively. Future minimum lease payments under noncancelable operating leases that have initial terms in excess of one year as of October 31, 2019 are as follows (in thousands): Year ending January 31, 2020 (3 months remaining) $ 8,758 2021 33,284 2022 40,804 2023 41,126 2024 40,506 Thereafter 231,750 Total $ 396,228 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 October 31, 2019 , the Company had a remaining minimum payment obligation of $175.0 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 condensed 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 October 31, 2019. As of October 31, 2019 and January 31, 2019, no material amounts were accrued.

Stockholders Equity

Stockholders Equity	9 Months Ended
	Oct. 31, 2019
Equity [Abstract]
Stockholders Equity	Stockholders Equity 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. As of October 31, 2019 , 289.9 million shares of Class A common stock and 259.1 million shares of Class B common stock were issued and outstanding. 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. Convertible Preferred Stock Prior to the Company’s Direct Listing, all of the 373.4 million shares of outstanding convertible preferred stock were converted into an equivalent number of shares of Class B common stock. Equity Incentive Plans The Company maintains two equity incentive plans: the 2009 Stock Plan (the “2009 Plan”) and the 2019 Stock Option and Incentive Plan (the “2019 Plan”). Upon the completion of the Direct Listing, the Company adopted the 2019 Plan and ceased to make any additional awards under the 2009 Plan and all shares that remained available for future issuance under the 2009 Plan at that time were canceled. The 2009 Plan continues to govern the terms of outstanding awards previously issued thereunder. The 2019 Plan 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 will 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 related information is as follows (in thousands, except years and per share data): Number of shares 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 (11,636 ) 0.97 Cancelled (254 ) 6.34 Outstanding at October 31, 2019 10,179 $ 4.25 6.44 $ 180,672 Stock options vested and exercisable at October 31, 2019 6,662 $ 1.25 5.23 $ 138,261 Stock options vested and expected to vest at October 31, 2019 10,179 $ 4.25 6.44 $ 180,672 As of October 31, 2019 , there was $18.4 million of total unrecognized stock-based compensation related to outstanding stock options, which will be recognized over a weighted average period of 4.8 years . Restricted Stock Units and Restricted Stock Awards A summary of Restricted Stock Units (“RSUs”) and Restricted Stock Awards (“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 Number of shares Weighted-average grant date fair value Unvested at January 31, 2019 63,114 $ 4.87 2,289 $ 7.23 Granted 22,099 18.73 505 13.60 Released (35,605 ) 4.46 (648 ) 5.89 Cancelled (3,252 ) 7.82 (10 ) 2.37 Unvested at October 31, 2019 46,356 $ 11.59 2,136 $ 9.17 As of October 31, 2019 , there was $347.4 million of total unrecognized stock-based compensation related to unvested RSUs, which will be recognized over a weighted average period of 1.5 years . As of October 31, 2019 , there was $15.6 million of total unrecognized stock-based compensation related to unvested RSAs, which will be recognized over a weighted average period of 3.2 years . 2019 Employee Stock Purchase Plan The Company’s 2019 Employee Stock Purchase Plan (“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 will 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 three and nine months ended October 31, 2019 , 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 October 31, 2019 , total unrecognized compensation cost related to the 2019 ESPP was $4.0 million which will be amortized over a weighted average period of 0.4 years . Stock-Based Compensation The Company recorded the total stock-based compensation expense as follows (in thousands): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 Cost of revenue $ 2,673 $ 40 $ 13,671 $ 701 Research and development 40,077 3,532 193,117 7,871 Sales and marketing 17,638 227 82,792 1,679 General and administrative 13,473 6,716 73,707 8,020 Total $ 73,861 $ 10,515 $ 363,287 $ 18,271 On June 20, 2019 , the Company recorded cumulative stock-based compensation of $245.1 million related to all then-outstanding RSUs as the performance vesting condition was satisfied upon the completion of the Direct Listing.

Other Income (Expense), Net

Other Income (Expense), Net	9 Months Ended
	Oct. 31, 2019
Other Income and Expenses [Abstract]
Other Income (Expense), Net	Other Income (Expense), Net Other income (expense), net consist of the following (in thousands): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 Interest income, net $ 3,872 $ 3,970 $ 12,727 $ 8,452 Unrealized gains (losses) on foreign exchange 44 (131 ) (1,066 ) (1,608 ) Transaction gains (losses) on foreign exchange 41 (358 ) (807 ) 144 Change in fair value of strategic investments 2,906 (61 ) 5,791 287 Other non-operating income (loss), net 272 (44 ) 678 (12 ) Other income (expense), net $ 7,135 $ 3,376 $ 17,323 $ 7,263

Income Taxes

Income Taxes	9 Months Ended
	Oct. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company computes its provision (benefit) for income taxes by applying the estimated annual effective tax rate to pretax income or loss and adjusts the provision for discrete tax items recorded in the period. For the three months ended October 31, 2019 and 2018 , the Company recorded a tax provision (benefit) of $(0.1) million and $0.3 million on pretax losses of $87.9 million and $47.4 million , respectively. The effective tax rates for the three months ended October 31, 2019 and 2018 were 0.1% and (0.7)% , respectively. For the three months ended October 31, 2019 , the Company maintained a full valuation allowance on its U.S. federal, state, and certain foreign jurisdictions net deferred tax assets as it was more likely than not that those deferred tax assets would not be realized. For the nine months ended October 31, 2019 and 2018 , the Company recorded a tax provision (benefit) of $(0.5) million and $0.8 million on pretax losses of $479.8 million and $103.5 million , respectively. The effective tax rates for the nine months ended October 31, 2019 and 2018 were 0.1% and (0.7)% , respectively. For the nine months ended October 31, 2019 , the Company maintained a full valuation allowance on its U.S. federal, state, and certain foreign jurisdictions net deferred tax assets as it was more likely than not that those deferred tax assets would not be realized. As of October 31, 2019 , the Company files tax returns in the U.S. federal, various state, and foreign jurisdictions. Due to the Company’s U.S. net operating loss carryforwards, our income tax returns generally remain subject to examination by federal and most state tax authorities. In July 2015, the U.S. Tax Court issued an opinion favorable to Altera Corporation (“Altera”) with respect to the exclusion of stock-based compensation from its intercompany cost-sharing arrangement. In June 2019, the U.S. Court of Appeals reversed the 2015 decision of the U.S. Tax Court. On July 22, 2019, Altera petitioned the Ninth Circuit to a rehearing of a larger panel of eleven Ninth Circuit judges. Altera’s petition for rehearing was denied on November 12, 2019. The Company is currently evaluating the potential impact on its consolidated financial statements for the year ending January 31, 2020.

Net Loss per Share Attributable

Net Loss per Share Attributable to Slack Common Stockholders	9 Months Ended
	Oct. 31, 2019
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): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 Numerator: Net loss attributable to Slack $ (89,161 ) $ (47,672 ) $ (482,055 ) $ (104,414 ) Denominator: Weighted average common shares outstanding 544,057 122,880 348,580 120,924 Net loss per share attributable to Slack common stockholders, basic and diluted $ (0.16 ) $ (0.39 ) $ (1.38 ) $ (0.86 ) 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 October 31, 2019 October 31, 2018 Convertible preferred stock — 373,372 Stock options 10,179 19,816 Unvested early exercised stock options 23 162 Restricted stock units 46,356 52,322 Restricted stock awards 2,136 2,214 Employee stock purchase plan 767 — Total antidilutive securities 59,461 447,886 The Company had 373.4 million shares of preferred stock outstanding that were converted to Class B common shares in connection with the Direct Listing. These securities were potentially dilutive, as outstanding shares of preferred stock, through the date of conversion of June 7, 2019.

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Oct. 31, 2019
Accounting Policies [Abstract]
Fiscal Year	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	Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”), regarding interim financial reporting. The accompanying condensed consolidated financial statements 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 condensed 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. The unaudited condensed consolidated balance sheet as of January 31, 2019 included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including certain notes required by U.S. GAAP on an annual reporting basis. In management's opinion, the unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the balance sheets, statements of comprehensive loss, statements of stockholders’ equity, and statements of cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full fiscal year or any future period. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Company’s final prospectus filed with the SEC pursuant to Rule 424(b) under the Securities Act of 1933, as amended, on June 20, 2019 , and as amended by the prospectus supplement dated September 5, 2019 (the “Prospectus”).
Consolidation	Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”), regarding interim financial reporting. The accompanying condensed consolidated financial statements 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 condensed 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. The unaudited condensed consolidated balance sheet as of January 31, 2019 included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including certain notes required by U.S. GAAP on an annual reporting basis. In management's opinion, the unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the balance sheets, statements of comprehensive loss, statements of stockholders’ equity, and statements of cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full fiscal year or any future period. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Company’s final prospectus filed with the SEC pursuant to Rule 424(b) under the Securities Act of 1933, as amended, on June 20, 2019 , and as amended by the prospectus supplement dated September 5, 2019 (the “Prospectus”).
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the condensed 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.
Recently Issued Accounting Standards Not Yet Adopted	Recently Issued Accounting Standards Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases , which supersedes the guidance in topic ASC 840, Leases. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. Under the standard, disclosures are required to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The Company will be required to recognize and measure leases existing at, or entered into after, the beginning of the earliest comparative period presented using a modified retrospective approach, with certain practical expedients available. For public companies, Topic 842 is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The Company has elected to use the extended transition period that allows the Company to delay adoption of new or revised accounting pronouncements applicable to public companies until such pronouncements are made applicable to private companies under the Jumpstart Our Business Startups Act. For as long as the Company remains an “emerging growth company,” the new guidance is effective for annual reporting periods beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020, and is required to be applied using a modified retrospective approach. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of this standard and currently believes the most significant impact upon adoption will be the recognition of material right-of-use assets and lease liabilities on its condensed consolidated balance sheets associated with operating leases. The Company does not believe this standard will have a material impact on its condensed consolidated statements of operations. 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 is currently evaluating the impact of the adoption of this standard on its condensed 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 fiscal years 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 condensed 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, and interim periods within those years, beginning after December 15, 2019, 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 condensed consolidated financial statements.
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.

Revenue and Contract Costs (Tab

Revenue and Contract Costs (Tables)	9 Months Ended
	Oct. 31, 2019
Revenue from Contract with Customer [Abstract]
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): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 United States $ 105,775 $ 67,345 $ 280,838 $ 177,923 International 62,950 38,303 167,681 100,662 Total $ 168,725 $ 105,648 $ 448,519 $ 278,585

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Oct. 31, 2019
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 October 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 327,471 $ — $ — $ 327,471 Commercial paper — 88,814 — 88,814 Total cash equivalents $ 327,471 $ 88,814 $ — $ 416,285 Marketable securities: Commercial paper $ — $ 37,369 $ — $ 37,369 U.S. agency securities — 13,995 — 13,995 U.S. government securities — 110,008 — 110,008 International government securities — 20,327 — 20,327 Corporate bonds — 115,933 — 115,933 Total marketable securities $ — $ 297,632 $ — $ 297,632 Noncurrent assets: Strategic investments $ — $ — $ 24,215 $ 24,215 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): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 Balance at beginning of period $ 17,496 $ 8,738 $ 12,334 $ 7,623 Purchases 3,813 710 9,283 1,610 Proceeds from liquidation — (37 ) (3,193 ) (171 ) Realized gains (losses) (466 ) (363 ) 2,227 (429 ) Unrealized gains relating to investments still held at reporting date 3,372 301 3,564 716 Balance at end of period $ 24,215 $ 9,349 $ 24,215 $ 9,349

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Oct. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Cash and Cash Equivalents and Marketable Securities	The following tables summarize the amortized cost, unrealized gains and losses, and estimated fair value of cash, cash equivalents, and marketable securities consisting of the following (in thousands): As of October 31, 2019 Amortized Unrealized Unrealized Fair value Cash and cash equivalents: Cash $ 60,189 $ — $ — $ 60,189 Money market funds 327,471 — — 327,471 Commercial paper 88,819 5 (10 ) 88,814 Total cash and cash equivalents 476,479 5 (10 ) 476,474 Marketable securities: Commercial paper $ 37,365 $ 7 $ (3 ) $ 37,369 U.S. agency securities 13,981 19 (6 ) 13,994 U.S. government securities 109,777 231 — 110,008 International government securities 20,313 15 — 20,328 Corporate bonds 115,807 138 (12 ) 115,933 Total marketable securities 297,243 410 (21 ) 297,632 Total cash, cash equivalents and marketable securities $ 773,722 $ 415 $ (31 ) $ 774,106 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 October 31, 2019 January 31, 2019 Due in one year $ 242,512 $ 506,297 Due in one to two years 55,120 154,004 Total $ 297,632 $ 660,301
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 October 31, 2019 January 31, 2019 Leasehold improvements $ 92,917 $ 86,258 Furniture and fixtures 26,229 19,693 Capitalized internal-use software costs 4,241 4,241 Computer equipment 3,093 2,222 Construction in progress 19,331 6,076 Property and equipment, gross 145,811 118,490 Less: accumulated depreciation and amortization (36,005 ) (30,131 ) Property and equipment, net $ 109,806 $ 88,359
Schedule of Intangible Assets	Intangible assets consist of the following (in thousands): October 31, 2019 Weighted-average Gross carrying Accumulated Net carrying Customer relationships 5.7 years $ 9,100 $ 1,679 $ 7,421 Developed technology 1.8 years 8,527 4,418 4,109 Assembled workforce 1.0 year 1,198 624 574 Total $ 18,825 $ 6,721 $ 12,104 January 31, 2019 Weighted-average Gross carrying Accumulated Net carrying 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 October 31, 2019 , expected amortization expense relating to intangible assets for each of the next five fiscal years and thereafter is as follows (in thousands): Year ending January 31, 2020 (3 months remaining) $ 1,033 2021 3,957 2022 2,618 2023 1,300 2024 1,300 Thereafter 1,896 Total $ 12,104

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Oct. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments Under Noncancelable Operating Leases	Future minimum lease payments under noncancelable operating leases that have initial terms in excess of one year as of October 31, 2019 are as follows (in thousands): Year ending January 31, 2020 (3 months remaining) $ 8,758 2021 33,284 2022 40,804 2023 41,126 2024 40,506 Thereafter 231,750 Total $ 396,228

Stockholders Equity (Tables)

Stockholders Equity (Tables)	9 Months Ended
	Oct. 31, 2019
Equity [Abstract]
Schedule of Stock Options Activity	A summary of stock option activity related information is as follows (in thousands, except years and per share data): Number of shares 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 (11,636 ) 0.97 Cancelled (254 ) 6.34 Outstanding at October 31, 2019 10,179 $ 4.25 6.44 $ 180,672 Stock options vested and exercisable at October 31, 2019 6,662 $ 1.25 5.23 $ 138,261 Stock options vested and expected to vest at October 31, 2019 10,179 $ 4.25 6.44 $ 180,672
Schedule of Restricted Stock Units and Restricted Stock Activity	A summary of Restricted Stock Units (“RSUs”) and Restricted Stock Awards (“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 Number of shares Weighted-average grant date fair value Unvested at January 31, 2019 63,114 $ 4.87 2,289 $ 7.23 Granted 22,099 18.73 505 13.60 Released (35,605 ) 4.46 (648 ) 5.89 Cancelled (3,252 ) 7.82 (10 ) 2.37 Unvested at October 31, 2019 46,356 $ 11.59 2,136 $ 9.17
Schedule of Stock-Based Compensation Expense	The Company recorded the total stock-based compensation expense as follows (in thousands): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 Cost of revenue $ 2,673 $ 40 $ 13,671 $ 701 Research and development 40,077 3,532 193,117 7,871 Sales and marketing 17,638 227 82,792 1,679 General and administrative 13,473 6,716 73,707 8,020 Total $ 73,861 $ 10,515 $ 363,287 $ 18,271

Other Income (Expense), Net (Ta

Other Income (Expense), Net (Tables)	9 Months Ended
	Oct. 31, 2019
Other Income and Expenses [Abstract]
Schedule of Other Income (Expense), Net	Other income (expense), net consist of the following (in thousands): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 Interest income, net $ 3,872 $ 3,970 $ 12,727 $ 8,452 Unrealized gains (losses) on foreign exchange 44 (131 ) (1,066 ) (1,608 ) Transaction gains (losses) on foreign exchange 41 (358 ) (807 ) 144 Change in fair value of strategic investments 2,906 (61 ) 5,791 287 Other non-operating income (loss), net 272 (44 ) 678 (12 ) Other income (expense), net $ 7,135 $ 3,376 $ 17,323 $ 7,263

Net Loss per Share Attributab_2

Net Loss per Share Attributable to Slack Common Stockholders (Tables)	9 Months Ended
	Oct. 31, 2019
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): Three Months Ended October 31, Nine Months Ended October 31, 2019 2018 2019 2018 Numerator: Net loss attributable to Slack $ (89,161 ) $ (47,672 ) $ (482,055 ) $ (104,414 ) Denominator: Weighted average common shares outstanding 544,057 122,880 348,580 120,924 Net loss per share attributable to Slack common stockholders, basic and diluted $ (0.16 ) $ (0.39 ) $ (1.38 ) $ (0.86 )
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 October 31, 2019 October 31, 2018 Convertible preferred stock — 373,372 Stock options 10,179 19,816 Unvested early exercised stock options 23 162 Restricted stock units 46,356 52,322 Restricted stock awards 2,136 2,214 Employee stock purchase plan 767 — Total antidilutive securities 59,461 447,886

Description of Business and S_3

Description of Business and Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended	9 Months Ended
	Oct. 31, 2019	Oct. 31, 2019
Direct Listing
Subsidiary, Sale of Stock [Line Items]
Financial advisory service, audit and legal fees associated with direct listing	$ 0	$ 30,400,000

Revenue and Contract Costs - Na

Revenue and Contract Costs - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	Jan. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue recognized on contract liabilities	$ 116,000,000	$ 66,900,000	$ 195,700,000	$ 103,000,000
Deferred commissions, net included in prepaid expenses and other current assets	9,600,000		9,600,000		$ 5,300,000
Deferred commissions, net included in other assets	19,200,000		19,200,000		$ 11,900,000
Amortization of deferred contract acquisition costs	2,200,000	900,000	5,522,000	1,965,000
Impairment loss related to deferred costs	$ 0	$ 0	$ 0	$ 0

Revenue and Contract Costs - Re

Revenue and Contract Costs - Remaining Performance Obligations (Details) $ in Millions	Oct. 31, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Future estimated revenue related to unsatisfied or partially satisfied performance obligations	$ 279.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations expected to be recognized (as a percent)	55.00%
Performance obligations expected to be satisfied, expected timing	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations expected to be recognized (as a percent)	36.00%
Performance obligations expected to be satisfied, expected timing	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations expected to be recognized (as a percent)	7.00%
Performance obligations expected to be satisfied, expected timing	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations expected to be recognized (as a percent)	1.00%
Performance obligations expected to be satisfied, expected timing	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations expected to be recognized (as a percent)	1.00%
Performance obligations expected to be satisfied, expected timing	12 months

Revenue and Contract Costs - Sc

Revenue and Contract Costs - Schedule of Revenue by Geographic Areas (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 168,725	$ 105,648	$ 448,519	$ 278,585
United States
Disaggregation of Revenue [Line Items]
Total revenues	105,775	67,345	280,838	177,923
International
Disaggregation of Revenue [Line Items]
Total revenues	$ 62,950	$ 38,303	$ 167,681	$ 100,662

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Jan. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 297,632	$ 660,301
Strategic investments	24,215	12,334
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	327,471	118,737
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	88,814
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	416,285	118,737
Marketable securities	297,632	660,301
Strategic investments	24,215	12,334
Fair Value, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	37,369	17,462
Fair Value, Recurring | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	13,995	44,879
Fair Value, Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	110,008	370,574
Fair Value, Recurring | International government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	20,327	36,734
Fair Value, Recurring | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	115,933	190,652
Fair Value, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	327,471	118,737
Fair Value, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	88,814
Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	327,471	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 equivalents	327,471	118,737
Fair Value, Recurring | Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	88,814	0
Marketable securities	297,632	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	37,369	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	13,995	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	110,008	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	20,327	36,734
Fair Value, Recurring | Level 2 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	115,933	190,652
Fair Value, Recurring | Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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 equivalents	88,814
Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities	0	0
Strategic investments	24,215	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 equivalents	0	$ 0
Fair Value, Recurring | Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 17,496	$ 8,738	$ 12,334	$ 7,623
Purchases	3,813	710	9,283	1,610
Proceeds from liquidation	0	(37)	(3,193)	(171)
Realized gains (losses)	(466)	(363)	2,227	(429)
Unrealized gains relating to investments still held at reporting date	3,372	301	3,564	716
Balance at end of period	$ 24,215	$ 9,349	$ 24,215	$ 9,349

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Cash and Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Jan. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	$ 476,474	$ 180,770
Marketable securities, amortized cost	297,243	660,599
Marketable securities, unrealized gains	410	151
Marketable securities, unrealized losses	(21)	(449)
Marketable securities, fair value	297,632	660,301
Total cash, cash equivalents and marketable securities, amortized cost	773,722	841,369
Total cash, cash equivalents and marketable securities, unrealized gains	415	151
Total cash, cash equivalents and marketable securities, unrealized losses	(31)	(449)
Total cash, cash equivalents and marketable securities, fair value	774,106	841,071
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	37,365	17,461
Marketable securities, unrealized gains	7	1
Marketable securities, unrealized losses	(3)	0
Marketable securities, fair value	37,369	17,462
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	13,981	44,886
Marketable securities, unrealized gains	19	7
Marketable securities, unrealized losses	(6)	(14)
Marketable securities, fair value	13,994	44,879
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	109,777	370,498
Marketable securities, unrealized gains	231	143
Marketable securities, unrealized losses	0	(67)
Marketable securities, fair value	110,008	370,574
International government securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	20,313	36,810
Marketable securities, unrealized gains	15	0
Marketable securities, unrealized losses	0	(76)
Marketable securities, fair value	20,328	36,734
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Marketable securities, amortized cost	115,807	190,944
Marketable securities, unrealized gains	138	0
Marketable securities, unrealized losses	(12)	(292)
Marketable securities, fair value	115,933	190,652
Total cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	476,479	180,770
Cash and cash equivalents, unrealized gains	5	0
Cash and cash equivalents, unrealized losses	(10)	0
Cash and cash equivalents, fair value	476,474	180,770
Cash
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	60,189	62,033
Cash and cash equivalents, fair value	60,189	62,033
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	327,471	118,737
Cash and cash equivalents, fair value	327,471	$ 118,737
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, amortized cost	88,819
Cash and cash equivalents, unrealized gains	5
Cash and cash equivalents, unrealized losses	(10)
Cash and cash equivalents, fair value	$ 88,814

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Marketable Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Jan. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Due in one year	$ 242,512	$ 506,297
Due in one to two years	55,120	154,004
Total	$ 297,632	$ 660,301

Balance Sheet Components - Sc_3

Balance Sheet Components - Schedule of Property and Equipment by Category (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Jan. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 145,811	$ 118,490
Less: accumulated depreciation and amortization	(36,005)	(30,131)
Property and equipment, net	109,806	88,359
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	92,917	86,258
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	26,229	19,693
Capitalized internal-use software costs
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,241	4,241
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,093	2,222
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 19,331	$ 6,076

Balance Sheet Components - Narr

Balance Sheet Components - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	Jan. 31, 2019
Concentration Risk [Line Items]
Depreciation	$ 6.7	$ 3.9	$ 17.3	$ 10.5
Amortization expense of intangible assets	$ 1	$ 0.7	$ 3.1	$ 0.8
Geographic Concentration Risk | United States | Property, Plant and Equipment
Concentration Risk [Line Items]
Concentration risk percentage			83.00%		87.00%

Balance Sheet Components - Sc_4

Balance Sheet Components - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Oct. 31, 2019	Jan. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 18,825	$ 18,825
Accumulated amortization	6,721	3,622
Net carrying amount	12,104	$ 15,203
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period		6 years 6 months
Gross carrying amount	9,100	$ 9,100
Accumulated amortization	1,679	704
Net carrying amount	7,421	$ 8,396
Developed technology
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period		2 years 7 months 6 days
Gross carrying amount	8,527	$ 8,527
Accumulated amortization	4,418	2,743
Net carrying amount	4,109	$ 5,784
Assembled workforce
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period		1 year 8 months 12 days
Gross carrying amount	1,198	$ 1,198
Accumulated amortization	624	175
Net carrying amount	$ 574	$ 1,023
Weighted Average | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period	5 years 8 months 12 days
Weighted Average | Developed technology
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period	1 year 9 months 18 days
Weighted Average | Assembled workforce
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining amortization period	1 year

Balance Sheet Components - Sc_5

Balance Sheet Components - Schedule of Expected Amortization Expense (Details) - USD ($) $ in Thousands	Oct. 31, 2019	Jan. 31, 2019
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2020 (3 months remaining)	$ 1,033
2021	3,957
2022	2,618
2023	1,300
2024	1,300
Thereafter	1,896
Net carrying amount	$ 12,104	$ 15,203

Revolving Credit Facility (Deta

Revolving Credit Facility (Details) - Line of Credit - Revolving Credit Facility - USD ($)	May 30, 2019	Oct. 31, 2019
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
Letter of credit amount outstanding		0
Remaining borrowing capacity		$ 215,000,000
Prime Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.25%
LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	1 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2019lawsuit	Mar. 31, 2019USD ($)	Apr. 30, 2018USD ($)	Oct. 31, 2019USD ($)	Oct. 31, 2018USD ($)	Oct. 31, 2019USD ($)	Oct. 31, 2018USD ($)
Long-term Purchase Commitment [Line Items]
Future minimum lease payments				$ 396,228,000		$ 396,228,000
Rent expense, net of sublease income				9,300,000	$ 7,600,000	26,300,000	$ 19,600,000
Number of class action lawsuits | lawsuit	7
San Francisco Office Facility | Office
Long-term Purchase Commitment [Line Items]
Future minimum lease payments				165,800,000		165,800,000
Tenant improvement reimbursements		$ 25,400,000
San Francisco Office Facility | Restricted Cash, Noncurrent
Long-term Purchase Commitment [Line Items]
Security deposit for lease arrangement		$ 18,000,000
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				$ 175,000,000		$ 175,000,000

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Noncancelable Operating Leases (Details) $ in Thousands	Oct. 31, 2019USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2020 (3 months remaining)	$ 8,758
2021	33,284
2022	40,804
2023	41,126
2024	40,506
Thereafter	231,750
Total	$ 396,228

Stockholders Equity - Narrative

Stockholders Equity - Narrative (Details) $ in Thousands	Jun. 20, 2019USD ($)	Jun. 06, 2019shares	Oct. 31, 2019USD ($)voteshares	Oct. 31, 2018USD ($)	Oct. 31, 2019USD ($)voteplanshares	Oct. 31, 2018USD ($)	Jun. 07, 2019shares
Class of Stock [Line Items]
Preferred stock, number of shares authorized (in shares)			100,000,000		100,000,000
Number of equity incentive plans | plan					2
Unrecognized stock based compensation expense related to options | $			$ 18,400		$ 18,400
Cumulative stock-based compensation expense | $			73,861	$ 10,515	$ 363,287	$ 18,271
Stock options
Class of Stock [Line Items]
Unrecognized stock based compensation expense related to options, weighted average period of recognition					4 years 9 months 18 days
Restricted stock units
Class of Stock [Line Items]
Unrecognized stock based compensation expense related to options, weighted average period of recognition					1 year 6 months
Unrecognized stock based compensation expense | $			347,400		$ 347,400
Cumulative stock-based compensation expense | $	$ 245,100
Restricted stock awards
Class of Stock [Line Items]
Unrecognized stock based compensation expense related to options, weighted average period of recognition					3 years 2 months 12 days
Unrecognized stock based compensation expense | $			$ 15,600		$ 15,600
Employee stock purchase plan
Class of Stock [Line Items]
Stock purchase offering period					6 months
Class A Common Stock
Class of Stock [Line Items]
Number of shares authorized for issuance (in shares)							5,000,000,000
Common stock, number of votes per share | vote			1		1
Number of shares issued (in shares)			289,900,000		289,900,000
Number of shares outstanding (in shares)			289,900,000		289,900,000
Number of shares issued under employee stock purchase plan (in shares)			300,000		300,000
Class B Common Stock
Class of Stock [Line Items]
Number of shares authorized for issuance (in shares)							700,000,000
Common stock, number of votes per share | vote			10		10
Number of shares issued (in shares)			259,100,000		259,100,000
Number of shares outstanding (in shares)			259,100,000		259,100,000
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
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 related to options, weighted average period of recognition					4 months 24 days
Unrecognized stock based compensation expense | $			$ 4,000		$ 4,000
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%

Stockholders Equity - Schedule

Stockholders Equity - Schedule of Stock Options (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Oct. 31, 2019USD ($)$ / sharesshares	Jan. 31, 2019USD ($)$ / sharesshares
Number of shares
Outstanding at beginning of period (in shares) | shares	18,406
Granted (in shares) | shares	3,663
Exercised (in shares) | shares	(11,636)
Cancelled (in shares) | shares	(254)
Outstanding at end of period (in shares) | shares	10,179	18,406
Stock options vested and exercisable at end of period, number of shares (in shares) | shares	6,662
Stock options vested and expected to vest at end of period, number of shares (in shares) | shares	10,179
Weighted-average exercise price per share
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 0.94
Granted (in dollars per share) | $ / shares	10.58
Exercised (in dollars per share) | $ / shares	0.97
Cancelled (in dollars per share) | $ / shares	6.34
Outstanding at end of period (in dollars per share) | $ / shares	4.25	$ 0.94
Stock options vested and exercisable at end of period, weighted-average exercise price per share (in dollars per share) | $ / shares	1.25
Stock options vested and expected to vest at end of period, weighted-average exercise price per share (in dollars per share) | $ / shares	$ 4.25
Weighted-average remaining contractual term (In years)
Outstanding, weighted-average remaining contractual term	6 years 5 months 8 days	6 years 1 month 13 days
Stock options vested and exercisable, weighted-average remaining contractual term	5 years 2 months 23 days
Stock options vested and expected to vest, weighted-average remaining contractual term	6 years 5 months 8 days
Aggregate intrinsic value
Outstanding, aggregate intrinsic value | $	$ 180,672	$ 177,012
Stock options vested and exercisable, aggregate intrinsic value | $	138,261
Stock options vested and expected to vest, aggregate intrinsic value | $	$ 180,672

Stockholders Equity - Schedul_2

Stockholders Equity - Schedule of Restricted Stock Units and Restricted Stock Awards (Details) shares in Thousands	9 Months Ended
	Oct. 31, 2019$ / sharesshares
Restricted stock units
Number of shares
Unvested at beginning of period (in shares) | shares	63,114
Granted (in shares) | shares	22,099
Released (in shares) | shares	(35,605)
Cancelled (in shares) | shares	(3,252)
Unvested at end of period (in shares) | shares	46,356
Weighted-average grant date fair value per share
Unvested at beginning of period (in dollars per share) | $ / shares	$ 4.87
Granted (in dollars per share) | $ / shares	18.73
Released (in dollars per share) | $ / shares	4.46
Cancelled (in dollars per share) | $ / shares	7.82
Unvested at end of period (in dollars per share) | $ / shares	$ 11.59
Restricted stock awards
Number of shares
Unvested at beginning of period (in shares) | shares	2,289
Granted (in shares) | shares	505
Released (in shares) | shares	(648)
Cancelled (in shares) | shares	(10)
Unvested at end of period (in shares) | shares	2,136
Weighted-average grant date fair value per share
Unvested at beginning of period (in dollars per share) | $ / shares	$ 7.23
Granted (in dollars per share) | $ / shares	13.60
Released (in dollars per share) | $ / shares	5.89
Cancelled (in dollars per share) | $ / shares	2.37
Unvested at end of period (in dollars per share) | $ / shares	$ 9.17

Stockholders Equity - Schedul_3

Stockholders Equity - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 73,861	$ 10,515	$ 363,287	$ 18,271
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	2,673	40	13,671	701
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	40,077	3,532	193,117	7,871
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	17,638	227	82,792	1,679
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 13,473	$ 6,716	$ 73,707	$ 8,020

Other Income (Expense), Net (De

Other Income (Expense), Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Other Income and Expenses [Abstract]
Interest income, net	$ 3,872	$ 3,970	$ 12,727	$ 8,452
Unrealized gains (losses) on foreign exchange	44	(131)	(1,066)	(1,608)
Transaction gains (losses) on foreign exchange	41	(358)	(807)	144
Change in fair value of strategic investments	2,906	(61)	5,791	287
Other non-operating income (loss), net	272	(44)	678	(12)
Other income (expense), net	$ 7,135	$ 3,376	$ 17,323	$ 7,263

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ (101)	$ 318	$ (504)	$ 753
Pretax losses	$ 87,867	$ 47,378	$ 479,767	$ 103,505
Effective tax rate	0.10%	(0.70%)	0.10%	(0.70%)

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	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Numerator:
Net loss attributable to Slack	$ (89,161)	$ (47,672)	$ (482,055)	$ (104,414)
Denominator:
Weighted average common shares outstanding (in shares)	544,057	122,880	348,580	120,924
Net loss per share attributable to Slack common stockholders, basic and diluted (in dollars per share)	$ (0.16)	$ (0.39)	$ (1.38)	$ (0.86)

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	Jun. 07, 2019	Oct. 31, 2019	Oct. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)		59,461	447,886
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	373,400	0	373,372
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)		10,179	19,816
Unvested early exercised stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)		23	162
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)		46,356	52,322
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)		2,136	2,214
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)		767	0

Net Loss per Share Attributab_5

Net Loss per Share Attributable to Slack Common Stockholders - Narrative (Details) - shares shares in Thousands	Jun. 07, 2019	Oct. 31, 2019	Oct. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities converted from convertible preferred stock to common stock (in shares)		59,461	447,886
Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities converted from convertible preferred stock to common stock (in shares)	373,400	0	373,372