Fastly (FSLY) 10-Q 8 Nov 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares shares in Millions	9 Months Ended
	Sep. 30, 2021	Oct. 29, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-38897
Entity Registrant Name	FASTLY, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-5411834
Entity Address, Address Line One	475 Brannan Street, Suite 300
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94107
City Area Code	844
Local Phone Number	432-7859
Title of 12(b) Security	Class A Common Stock, $0.00002 par value
Trading Symbol	FSLY
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		117.5
Entity Central Index Key	0001517413
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 282,131	$ 62,900
Marketable securities, current	361,290	131,283
Accounts receivable, net of allowance for credit losses of $3,173 and $3,248 as of September 30, 2021 and December 31, 2020, respectively	54,234	50,258
Restricted cash	0	87
Prepaid expenses and other current assets	22,230	16,728
Total current assets	719,885	261,256
Marketable securities, noncurrent	429,489	20,448
Property and equipment, net	147,729	95,979
Operating right-of-use assets	70,149	60,019
Goodwill	635,635	635,590
Intangible assets, net	107,905	121,742
Other assets	28,142	24,917
Total assets	2,138,934	1,219,951
Current liabilities:
Accounts payable	7,766	9,150
Accrued expenses	36,063	34,334
Finance lease liabilities, current	18,675	11,033
Operating lease liabilities, current	20,007	19,895
Other current liabilities	24,758	19,677
Total current liabilities	107,269	94,089
Long-term debt	932,305	0
Finance lease liabilities, noncurrent	24,659	14,707
Operating lease liabilities, noncurrent	54,066	44,890
Other long-term liabilities	5,056	4,400
Total liabilities	1,123,355	158,086
Commitments and contingencies (Note 10)
Stockholders’ equity:
Class A and Class B common stock	2	2
Additional paid-in capital	1,469,366	1,350,050
Accumulated other comprehensive income (loss)	(420)	6
Accumulated deficit	(453,369)	(288,193)
Total stockholders’ equity	1,015,579	1,061,865
Total liabilities and stockholders’ equity	$ 2,138,934	$ 1,219,951

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 3,173	$ 3,248

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenue	$ 86,735	$ 70,638	$ 256,613	$ 208,225
Cost of revenue	41,244	29,292	119,058	86,254
Gross profit	45,491	41,346	137,555	121,971
Operating expenses:
Research and development	32,528	18,271	91,862	49,224
Sales and marketing	39,288	22,568	110,494	66,416
General and administrative	28,609	23,961	97,564	56,199
Total operating expenses	100,425	64,800	299,920	171,839
Loss from operations	(54,934)	(23,454)	(162,365)	(49,868)
Interest income	280	353	730	1,450
Interest expense	(1,555)	(410)	(3,652)	(1,097)
Other income	41	69	155	418
Loss before income taxes	(56,168)	(23,442)	(165,132)	(49,097)
Income tax expense	30	336	44	1,131
Net loss	$ (56,198)	$ (23,778)	$ (165,176)	$ (50,228)
Net loss per share attributable to common stockholders, basic (in US dollar per share)	$ (0.48)	$ (0.22)	$ (1.43)	$ (0.50)
Net loss per share attributable to common stockholders, diluted (in US dollar per share)	$ (0.48)	$ (0.22)	$ (1.43)	$ (0.50)
Weighted-average shares used in computing net loss per share attributable to common stockholder, basic (in shares)	116,475	105,942	115,320	100,413
Weighted-average shares used in computing net loss per share attributable to common stockholder, diluted (in shares)	116,475	105,942	115,320	100,413

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Other Comprehensive Income [Abstract]
Net loss	$ (56,198)	$ (23,778)	$ (165,176)	$ (50,228)
Other comprehensive loss:
Foreign currency translation loss	(186)	(68)	(228)	(149)
Gain (loss) on investments in available-for-sale-securities, net of tax	27	(193)	(198)	77
Total other comprehensive loss	(159)	(261)	(426)	(72)
Comprehensive loss	$ (56,357)	$ (24,039)	$ (165,602)	$ (50,300)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Class B	Common StockCommon Class A	Common StockCommon Class AVesting of restricted stock units	Common StockCommon Class ARevest Shares	Common StockCommon Class B	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated DeficitCumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Dec. 31, 2019				60,954,694			33,863,021
Beginning balance at Dec. 31, 2019	$ 257,652	$ (252)		$ 1			$ 1	$ 449,463	$ 196	$ (192,009)	$ (252)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued (in shares)				6,900,000
Shares issued	274,177							274,177
Vesting of early exercised stock options (in shares)							94,048
Vesting of early exercised stock options	401							401
Vesting of restricted stock units/awards (in shares)					905,093
Shares issued under ESPP (in shares)				226,288
Shares issued under ESPP	4,247							4,247
Exercise of stock options (in shares)				3,802,613
Exercise of stock options	12,953							12,953
Exercise of common stock warrants (in shares)							144,635
Stock-based compensation	35,990							35,990
Conversion of stock (in shares)			144,635,000	22,727,685			(22,727,685)
Net loss	(50,228)									(50,228)
Other comprehensive income (loss)	(72)								(72)
Ending balance (in shares) at Sep. 30, 2020				95,516,373			11,374,019
Ending balance at Sep. 30, 2020	534,868			$ 1			$ 1	777,231	124	(242,489)
Beginning balance (in shares) at Jun. 30, 2020				90,321,462			14,716,313
Beginning balance at Jun. 30, 2020	541,913			$ 1			$ 1	760,237	385	(218,711)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of early exercised stock options (in shares)							28,730
Vesting of early exercised stock options	127							127
Vesting of restricted stock units/awards (in shares)					844,635
Exercise of stock options (in shares)				979,252
Exercise of stock options	4,122							4,122
Stock-based compensation	12,745							12,745
Conversion of stock (in shares)			0	3,371,024			(3,371,024)
Net loss	(23,778)									(23,778)
Other comprehensive income (loss)	(261)								(261)
Ending balance (in shares) at Sep. 30, 2020				95,516,373			11,374,019
Ending balance at Sep. 30, 2020	534,868			$ 1			$ 1	777,231	124	(242,489)
Ending balance (in shares) at Dec. 31, 2020				103,394,496			10,228,700
Ending balance at Dec. 31, 2020	1,061,865			$ 1			$ 1	1,350,050	6	(288,193)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of early exercised stock options (in shares)							43,095
Vesting of early exercised stock options	192							192
Vesting of restricted stock units/awards (in shares)					1,520,101	336,186
Shares issued under ESPP (in shares)				153,678
Shares issued under ESPP	$ 5,719							5,719
Exercise of stock options (in shares)	1,527,000			1,527,091
Exercise of stock options	$ 9,094							9,094
Stock-based compensation	104,311							104,311
Conversion of stock (in shares)				10,271,795			(10,271,795)
Conversion of stock				$ 1			$ (1)
Net loss	(165,176)									(165,176)
Other comprehensive income (loss)	(426)								(426)
Ending balance (in shares) at Sep. 30, 2021				117,203,347			0
Ending balance at Sep. 30, 2021	1,015,579			$ 2			$ 0	1,469,366	(420)	(453,369)
Beginning balance (in shares) at Jun. 30, 2021				106,259,339			9,708,299
Beginning balance at Jun. 30, 2021	1,029,090			$ 1			$ 1	1,426,520	(261)	(397,171)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of early exercised stock options (in shares)							14,366
Vesting of early exercised stock options	64							64
Vesting of restricted stock units/awards (in shares)					611,020	112,062
Exercise of stock options (in shares)				498,261
Exercise of stock options	3,489							3,489
Stock-based compensation	39,293							39,293
Conversion of stock (in shares)				9,722,665			(9,722,665)
Conversion of stock				$ 1			$ (1)
Net loss	(56,198)									(56,198)
Other comprehensive income (loss)	(159)								(159)
Ending balance (in shares) at Sep. 30, 2021				117,203,347			0
Ending balance at Sep. 30, 2021	$ 1,015,579			$ 2			$ 0	$ 1,469,366	$ (420)	$ (453,369)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (56,198)	$ (23,778)	$ (165,176)	$ (50,228)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense			20,710	14,266
Amortization of intangible assets	5,300	100	15,929	145
Amortization of right-of-use assets and other			19,818	15,824
Amortization of debt discount and issuance costs			2,235	58
Amortization of deferred contract costs	1,600	900	4,567	2,375
Stock-based compensation			100,900	34,752
Provision for credit losses			41	1,212
Interest paid on finance leases	(524)	(186)	(1,259)	(454)
Loss on disposals of property and equipment			(177)	(133)
Other adjustments			1,496	176
Changes in operating assets and liabilities:
Accounts receivable			(4,017)	(6,669)
Prepaid expenses and other current assets			(5,502)	(3,778)
Other assets			(7,320)	(7,410)
Accounts payable			(1,653)	7,046
Accrued expenses			2,713	17,224
Operating lease liabilities			(19,735)	(12,852)
Other liabilities			5,856	(321)
Net cash (used in) provided by operating activities			(30,574)	11,233
Cash flows from investing activities:
Purchases of marketable securities			(777,569)	(204,361)
Sales of marketable securities			64,236	143,241
Maturities of marketable securities			72,853	83,718
Purchase of property and equipment			(31,267)	(23,602)
Proceeds from sale of property and equipment			291	150
Capitalized internal-use software			(10,299)	(4,082)
Purchases of intangible assets			(2,092)	(1,811)
Net cash used in investing activities			(683,847)	(6,747)
Cash flows from financing activities:
Proceeds from follow-on public offering, net of underwriting fees			0	274,896
Payments of costs related to initial public offering			0	(675)
Issuance of convertible note, net of issuance costs			930,775	0
Payments of other debt issuance costs			(1,351)	0
Repayments of finance lease liabilities	(3,985)	(1,001)	(10,564)	(3,901)
Proceeds from employee stock purchase plan			5,994	6,206
Proceeds from exercise of vested stock options			9,094	12,953
Net cash provided by financing activities			933,948	289,479
Effects of exchange rate changes on cash, cash equivalents, and restricted cash			(383)	(139)
Net increase in cash, cash equivalents, and restricted cash			219,144	293,826
Cash, cash equivalents, and restricted cash at beginning of period			63,880	86,229
Cash, cash equivalents, and restricted cash at end of period	283,024	380,055	283,024	380,055
Supplemental disclosure of cash flow information:
Cash paid for interest			1,379	758
Cash paid for income taxes, net of refunds received			240	1,000
Property and equipment additions not yet paid in cash			443	9,613
Vesting of early-exercised stock options			192	401
Cashless exercise of common stock warrants			0	1,557
Stock-based compensation capitalized to internal-use software	2,600	600	3,411	1,238
Assets obtained in exchange for operating lease obligations	12,264	4,817	25,745	15,095
Assets obtained in exchange for finance lease obligations	12,861	3,510	28,399	11,352
Reconciliation of cash, cash equivalents, and restricted cash as shown in the statements of cash flows:
Cash and cash equivalents	282,131	309,968	282,131	309,968
Restricted cash	0	70,087	0	70,087
Restricted cash included in other assets	893	0	893	0
Total cash, cash equivalents, and restricted cash	$ 283,024	$ 380,055	$ 283,024	$ 380,055

Nature of Business

Nature of Business	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Fastly, Inc. has built an edge cloud platform that can process, serve, and secure its customer’s applications as close to their end users as possible. As of September 30, 2021, our edge network spans across 68 markets around the world. We were incorporated in Delaware in 2011 and are headquartered in San Francisco, California. As used herein, "Fastly," "we," "our," "the Company," and similar terms include Fastly, Inc. and its subsidiaries, unless the context indicates otherwise, Conversion of dual class common stock structure On October 12, 2020, the outstanding shares of our Class B common stock represented less than 10% of the aggregate number of shares of the then outstanding Class A common stock and Class B common stock. As a result, all outstanding shares of Class B common stock automatically converted into the same number of shares of Class A common stock on July 12, 2021, pursuant to the terms of our amended and restated certificate of incorporation (the "Certificate"). Upon the conversion, outstanding options denominated in shares of Class B common stock issued under any of our equity incentive plans remained unchanged, except that they now represent the right to receive shares of Class A common stock on exercise. In accordance with the Certificate, the shares of Class B common stock that converted to Class A common stock were retired and will not be reissued by us.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The interim unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with United States generally accepted accounting principles ("U.S. GAAP") along with instructions to Form 10-Q and Article 10 of Securities and Exchange Commission ("SEC") Regulation S-X. Certain changes in presentation have been made to conform the prior period presentation to the current period reporting. Such reclassifications did not affect total revenues, operating income, or net income. We have made certain presentation changes to distinguish and disclose as a separate line item, our Marketable securities, noncurrent balance from our Other assets line in the Condensed Consolidated Balance Sheets. We have made certain presentation changes to distinguish and disclose as separate line items, the amortization of intangible assets and depreciation expenses within operating cash flows in the Condensed Consolidated Statements of Cash Flows. We have also made certain presentation changes to retroactively adjust for the effects of Accounting Standards Codification No. 842, Leases ("ASC 842") that was adopted as part of our form 10-K filing on March 1, 2021 with an adoption effective date of January 1, 2020, using the modified retrospective method. Changes to our Condensed Consolidated Statements of Cash Flows include separately disclosing under operating cash flows the amortization of right-of-use assets and other, and payments associated with operating lease liabilities. We have also updated our supplemental cash flow disclosures accordingly to disclose assets obtained in exchange for operating lease obligations and assets obtained in exchange for finance lease obligations, in accordance with the disclosure requirements of ASC 842. We have also updated our Condensed Consolidated Statement of Stockholders' Equity to include the impact to accumulated deficit upon adoption for the activity in the three and nine months ended September 30, 2020. The following tables show the affected line items within the condensed consolidated financial statements (in millions): Condensed Consolidated Statement of Stockholders' Equity Three Months Ended September 30, 2020 As previously reported Adjustments As adjusted (in thousands) Accumulated Deficit: Balance as of June 30, 2020 $ (218,459) $ (252) $ (218,711) Balance as of September 30, 2020 $ (242,237) $ (252) $ (242,489) Total Stockholders' Equity Balance as of June 30, 2020 $ 542,165 $ (252) $ 541,913 Balance as of September 30, 2020 $ 535,120 $ (252) $ 534,868 Nine months ended September 30, 2020 As previously reported Adjustments As adjusted (in thousands) Accumulated Deficit: Balance as of December 31, 2019 $ (192,009) $ — $ (192,009) Change in accounting policy $ — $ (252) $ (252) Balance as of September 30, 2020 $ (242,237) $ (252) $ (242,489) Total Stockholders' Equity Balance as of December 31, 2019 $ 257,652 $ — $ 257,652 Change in accounting policy $ — $ (252) $ (252) Balance as of September 30, 2020 $ 535,120 $ (252) $ 534,868 Condensed Consolidated Statement of Cash Flows Nine months ended September 30, 2020 As previously reported Adjustments As adjusted (in thousands) Cash flows from operating activities: Amortization of deferred rent $ 2,941 $ (2,941) $ — Amortization of right-of-use asset and other — 15,824 15,824 Other adjustments 207 (31) 176 Operating lease liabilities — (12,852) (12,852) Net cash used in operating activities 11,233 — 11,233 Cash flows from investing activities: Purchase of property and equipment (24,443) 841 (23,602) Net cash provided by investing activities (7,588) 841 (6,747) Cash flows from financing activities: Repayments of capital lease liabilities (3,060) 3,060 — Repayments of finance lease liabilities — (3,901) (3,901) Net cash provided by financing activities $ 290,320 $ (841) $ 289,479 Supplemental disclosure of cash flow information: Capital lease outstanding on current year addition $ 5,439 $ (5,439) $ — Assets obtained in exchange for operating lease obligations $ — $ 15,095 $ 15,095 Assets obtained in exchange for finance lease obligations $ — $ 11,352 11,352 Principles of Consolidation The accompanying interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Unaudited Interim Financial Statements The accompanying interim condensed consolidated balance sheet as of September 30, 2021, the related interim condensed consolidated statements of operations, the condensed consolidated statements of comprehensive loss, and the condensed consolidated statements of stockholders' equity for the three and nine months ended September 30, 2021 and 2020, the condensed consolidated statements of cash flows for the nine months ended September 30, 2021 and 2020, and the related footnote disclosures are unaudited. The unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. GAAP. In management’s opinion, the unaudited financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, which include only normal recurring adjustments necessary for the fair presentation of our financial position as of September 30, 2021. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results expected for the full fiscal year or any other periods. Use of Estimates The preparation of our condensed consolidated financial statements requires us to make estimates, judgments, and assumptions that affect the reported amounts of assets, liabilities, revenue, costs and expenses and related disclosures. Actual results and outcomes could differ significantly from our estimates, judgments, and assumptions. Significant estimates, judgments, and assumptions used in these financial statements include, but are not limited to, those related to revenue, accounts receivable and related reserves, fair value of assets acquired and liabilities assumed for business combinations, useful lives and realizability of long-lived assets including our goodwill and intangible assets, income tax reserves and accounting for stock-based compensation. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. The effects of material revisions in estimates are reflected in the condensed consolidated financial statements in the period of change and prospectively from the date of the change in estimate. The ongoing global COVID-19 pandemic has adversely impacted many operational aspects of our business and may continue to do so in the future. Since the start of the pandemic, we have assessed the impact that COVID-19 had on our results of operations, including, but not limited to an assessment of our allowance for credit losses, the carrying value of short-term and long-term marketable securities, the carrying value of goodwill and other long-lived assets, and the impact on revenue recognition and cost of revenues. The future impacts of the pandemic and any resulting economic impact are largely unknown and are continuing to evolve. We will continue to actively monitor the impact that COVID-19 has on the results of our business operations, and may make decisions required by federal, state or local authorities, or that are determined to be in the best interests of our employees, customers, partners, suppliers and stockholders. As a result, our estimates and judgments may change materially as new events occur or additional information becomes available to us. Concentrations of Credit Risk Financial instruments that potentially subject us to significant concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, and accounts receivable. The primary focus of our investment strategy is to preserve capital and meet liquidity requirements. Our investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. To manage the risk exposure, we invest cash equivalents and marketable securities in a variety of fixed income securities, including government and investment-grade debt securities and money market funds. We place our cash primarily in checking and money market accounts with reputable financial institutions. Deposits held with these financial institutions may exceed the amount of insurance provided on such deposits, if any. Concentrations of credit risk with respect to accounts receivable are primarily limited to certain customers to which we make substantial sales. Our customer base consists of a large number of geographically dispersed customers diversified across several industries. To reduce this risk, we routinely assess the financial strength of our customers. Based on such assessments, we believe that our accounts receivable credit risk exposure is limited. No customer accounted for more than 10% of revenue for the three and nine months ended September 30, 2021. No customer accounted for more than 10% of revenue for the three months ended September 30, 2020. One customer accounted for 11% of revenue for the nine months ended September 30, 2020. As of September 30, 2021, we had one customer that accounted for more than 10% of the total accounts receivable balance. As of December 31, 2020, we had a different customer that accounted for more than 10% of the total accounts receivable balance. Significant Accounting Policies Other than the following updates to our accounting policies in conjunction with the issuance of the convertible debt in March 2021, there have been no material changes to our significant accounting policies as compared to those described in “Note 2 – Summary of Significant Accounting Policies” of our Annual Report on Form 10-K for the fiscal year ended December 31, 2020. Convertible Debt We early adopted ASU 2020-06 as of January 1, 2021, which in effect, allows for the separation models for convertible debt that contain cash conversion features accounted for as a cash conversion or beneficial conversion features to be removed. We evaluated the terms of our debt in line with ASU 2020-06 and concluded that the instrument does not require separation and that there were no other derivatives that required separation. We have combined these features with the host contract and we account for our convertible debt as a single liability in long-term debt on our condensed consolidated balance sheet. The carrying amount of the liability is based on the gross proceeds, net of the unamortized transaction costs incurred related to the issuance of the convertible debt instrument. This difference represents a debt discount that is amortized to interest expense over the term of the convertible debt instrument using the effective interest rate method. We apply the if-converted method for calculation of diluted earnings per share for our convertible debt instrument. Recently Adopted Accounting Pronouncements On December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740), which simplifies the accounting for income taxes, primarily by eliminating certain exceptions to ASC 740. This standard is effective for fiscal periods beginning after December 15, 2020. We adopted this standard on January 1, 2021. The adoption of this standard did not have a material impact on our consolidated financial statements. In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40). The update removes separation models for convertible debt that contain cash conversion features accounted for as a cash conversion or beneficial conversion features. Under this ASU, these features will be combined with the host contract. ASU 2020-06 does not impact the accounting treatment for conversion features that are accounted for as a derivative under Topic 815. The update also requires the application of the if-converted method to be used for convertible instruments and the effect of potential share settlement be included in the diluted earnings per share calculation when an instrument may be settled in cash or shares. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2021, and interim periods within those fiscal years. The amendment is to be adopted through either a fully retrospective or modified retrospective method of transition, only at the beginning of an entity's fiscal year. Early adoption is permitted. We have elected to early adopt the standard as of January 1, 2021 using the modified retrospective method of transition. We evaluated the terms of our debt and concluded that the instrument does not require separation and that there were no other derivatives that required separation. As a result, there is no equity component and we recorded the convertible note as a single liability within long-term debt on our Condensed Consolidated Balance Sheet. We apply the if-converted method for calculation of diluted earnings per share for our convertible debt instruments. Other Recent Accounting Pronouncements Other recently issued accounting pronouncements are not expected to have a material impact on our condensed consolidated financial statements.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Revenue recognition Revenue is recognized upon transfer of control of promised products or services to customers in an amount that reflects the consideration we expect to receive in exchange for those products or services. The processing and recording of certain revenue requires a manual process, which uses a complex set of procedures to generate complete and accurate data to record these revenue transactions. We enter into contracts that can include various combinations of products and services, each of which are distinct and accounted for as separate performance obligations. Revenue is recognized net of any taxes collected from customers, which are subsequently remitted to governmental authorities. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account. Our contracts with customers often include promises to transfer multiple products and services to a customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment. For contracts with multiple performance obligations, we allocate the contract transaction price to each performance obligation using our estimate of the standalone selling price ("SSP") of each distinct good or service in the contract. Judgment is required to determine the SSP for each distinct performance obligation. We analyze separate sales of our products and services as a basis for estimating the SSP of our products and services. We then use the SSP as the basis for allocating the transaction price when our product and services are sold together in a contract with multiple performance obligations. In instances where SSP is not directly observable, such as when we do not sell the product or service separately, we determine the SSP using information that may include market conditions and other observable inputs. We typically have more than one SSP for individual products and services due to the stratification of those products and services by customers and circumstances. In these instances, we may use information, such as geographic region and distribution channel, in determining the SSP. The transaction price in a contract for usage-based services is typically equal to the minimum commit price in the contract less any discounts provided. The transaction price in a contract that does not contain usage-based services is equal to the total contract value. Because our typical contracts represent distinct services delivered over time with the same pattern of transfer to the customer, usage-based consideration primarily related to actual consumption over the minimum commit levels is allocated to the period to which it relates. The amount of consideration recognized for usage above the minimum commit price is limited to the amount we expect to be entitled to receive in exchange for providing services. We have elected to apply the practical expedient for estimating and disclosing the variable consideration when variable consideration is allocated entirely to a wholly unsatisfied performance obligation or to a wholly unsatisfied promise to transfer a distinct good or service that forms part of a single performance obligation from our remaining performance obligations under these contracts. Performance obligations represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by us. These obligations can be content delivery, security, subscription services, professional services, support, edge cloud platform services, and others. Accordingly, our revenue is recognized over time, consistent with the pattern of benefit provided to the customer over the term of the agreement. At times, customers may request changes that either amend, replace, or cancel existing contracts. Judgment is required to determine whether the specific facts and circumstances within the contracts should be accounted for as a separate contract or as a modification. In contracts where there are timing differences between when we transfer a promised good or service to the customer and when the customer pays for that good or service, we have determined our contracts do not include a significant financing component. We have also elected the practical expedient to not measure financing components for any contract where the timing difference is less than one year. Nature of products and services We primarily derive revenue from the sale of services to customers executing contracts in which the standard contract term is one year, although terms may vary by contract. Most of our contracts are non-cancelable over the contractual term. The majority of our usage based contracts commit the customer to a minimum monthly level of usage and specify the rate at which the customer must pay for actual usage above the monthly minimum. Beginning in the fourth quarter of 2020, we also offer subscriptions to access a unified security web application and application programming interface at a fixed rate. Revenue by geography is based on the billing address of the customer. Aside from the United States, no other single country accounted for more than 10% of revenue for the three and nine months ended September 30, 2021 and the three months ended September 30, 2020. Aside from the United States, the only other country with greater than 10% of revenue was Singapore, which accounted for 11% of revenue for the nine months ended September 30, 2020. The following table presents our net revenue by geographic region: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) (in thousands) United States $ 62,287 $ 49,140 $ 179,860 $ 136,194 Asia Pacific 9,804 10,306 27,969 34,157 Europe 8,550 8,003 25,969 23,549 All other 6,094 3,189 22,815 14,325 Total revenue $ 86,735 $ 70,638 $ 256,613 $ 208,225 The majority of our revenue is derived from enterprise customers, which are defined as customers with revenue in excess of $100,000 over the previous 12-month period. The following table presents our net revenue for enterprise and non-enterprise customers: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Enterprise customers $ 76,006 $ 63,353 $ 226,622 $ 186,490 Non-enterprise customers 10,729 7,285 29,991 21,735 Total revenue $ 86,735 $ 70,638 $ 256,613 $ 208,225 Contract balances The timing of revenue recognition may differ from the timing of invoicing to customers. We have an unconditional right to consideration when we invoice our customers and record a receivable. We record a contract asset when revenue is recognized prior to invoicing, or a contract liability (deferred revenue) when revenue is recognized subsequent to invoicing. Deferred revenue includes amounts billed to customers for which revenue has not been recognized and consists of the unearned portions of edge cloud platform usage and billings to customers for our security subscription services. Amounts that have been invoiced for annual subscriptions, but not collected, are recorded in accounts receivable and in unearned revenue or in revenue depending on whether services have been delivered to the customer. Our payment terms and conditions vary by contract type. Payment terms on invoiced amounts are at an average of 40 days. The following table presents our contract assets and contract liabilities as of September 30, 2021 and as of December 31, 2020: As of September 30, 2021 As of December 31, 2020 (in thousands) Contract assets $ 181 $ 387 Contract liabilities $ 24,817 $ 18,020 The following table presents the revenue recognized during the three and nine months ended September 30, 2021 and 2020 from amounts included in the contract liability at the beginning of the period: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Revenue recognized in the period from amounts included in contract liability at the beginning of the period $ 8,815 $ 37 $ 13,942 $ 310 Remaining performance obligations As of September 30, 2021, we had $147.6 million of remaining performance obligations, which includes deferred revenue and amounts that will be invoiced and recognized in future periods, respectively. We apply the practical expedient of ASC 606, which gives us the optional exemption from disclosing certain information about our remaining performance obligations for our service contracts for which the original contract duration is one year or less, such as the aggregate transaction price allocated to the performance obligations that are unsatisfied (or partially unsatisfied) as of the end of the reporting period. The typical contract term is one year, although terms may vary by contract. As of September 30, 2021, we expect to recognize 84% of this balance over the next 12 months and the remainder within the following year. Costs to obtain a contract We capitalize incremental costs associated with obtaining customer contracts, specifically for sales commissions. These costs are deferred on our Condensed Consolidated Balance Sheets and are amortized over the expected period of benefit on a straight-line basis. Based on the nature of our unique technology and services, the rate at which we continually enhance and update our technology, and our historical customer retention, the expected period of benefit is determined to be approximately five years. Amortization is recorded within the sales and marketing line item on the accompanying Condensed Consolidated Statements of Operations. The incremental costs associated with obtaining customer contracts, the majority of which are deferred commissions, are included in other assets on the accompanying Condensed Consolidated Balance Sheets. As of September 30, 2021 and December 31, 2020, our costs to obtain contracts were as follows: As of September 30, 2021 As of December 31, 2020 (in thousands) Deferred contract costs, net $ 23,067 $ 19,332

Investments and Fair Value Meas

Investments and Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Investments and Fair Value Measurements	Investments and Fair Value Measurements Our total cash, cash equivalents and marketable securities consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Cash and cash equivalents: Cash $ 21,832 $ 21,273 Money market funds 259,699 36,629 Commercial paper — 4,998 Municipal securities 400 — Certificate of deposit 200 — Total cash and cash equivalents $ 282,131 $ 62,900 Marketable securities: Corporate notes and bonds $ 3,129 $ 14,314 Commercial paper 134,015 41,445 U.S. Treasury securities 190,183 75,524 Foreign government and supranational securities 10,025 — Municipal securities 2,250 — Asset-backed securities 21,688 — Total marketable securities, current $ 361,290 $ 131,283 Corporate notes and bonds 131,177 — U.S. Treasury securities 220,291 20,448 Municipal securities 2,330 — Asset-backed securities 55,332 — Foreign government and supranational securities 20,359 — Total marketable securities, non-current $ 429,489 $ 20,448 Total marketable securities $ 790,779 $ 151,731 Total cash, cash equivalents and marketable securities $ 1,072,910 $ 214,631 Cash equivalents include investments with maturity date of three months or less . As of September 30, 2021 and December 31, 2020, all of our securities are classified as available-for-sale. The majority of these securities have contractual maturities of one year or less and accordingly, we have classified these securities as short-term. These short-term securities are included within the marketable securities, current financial statement line item on our Condensed Consolidated Balance Sheet. As of September 30, 2021 and December 31, 2020, we also held certain securities that have contractual maturities greater than one year. As we intend to hold these securities for more than 12 months, we have classified all securities that we intend to hold for more than 12 months as long-term. These securities are included within the marketable securities, noncurrent financial statement line item on our Condensed Consolidated Balance Sheet. Available-for-Sale Investments The following table summarizes adjusted cost, gross unrealized gains and losses, and fair value related to available-for-sale securities classified as marketable securities on the accompanying Condensed Consolidated Balance Sheets as of September 30, 2021 and December 31, 2020: As of September 30, 2021 Amortized Gross Gross Fair (in thousands) Corporate notes and bonds $ 134,282 $ 42 $ (18) $ 134,306 Commercial paper 134,038 — (23) 134,015 U.S. Treasury securities 410,542 6 (74) 410,474 Municipal securities 4,578 2 — 4,580 Asset-backed securities 77,038 — (18) 77,020 Foreign government and supranational securities 30,394 — (10) 30,384 Total available-for-sale investments $ 790,872 $ 50 $ (143) $ 790,779 As of December 31, 2020 Amortized Gross Gross Fair (in thousands) Corporate notes and bonds $ 14,297 $ 17 $ — $ 14,314 Commercial paper 41,445 — — 41,445 U.S. Treasury securities 95,884 93 (5) 95,972 Total available-for-sale investments $ 151,626 $ 110 $ (5) $ 151,731 There were no securities in a continuous loss position for 12 months or longer as of September 30, 2021 and December 31, 2020. Investments are reviewed periodically to identify possible other-than-temporary impairments. No impairment loss has been recorded on the securities included in the tables above, as we believe that the decrease in fair value of these securities is temporary. Fair Value of Financial Instruments For certain of our financial instruments, including cash held in banks, accounts receivable, and accounts payable, the carrying amounts approximate fair value due to their short maturities, and are therefore excluded from the fair value tables below. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There is a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1—Observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3—Unobservable inputs that are supported by little or no market activity, which require management judgment or estimation. We measure our cash equivalents, marketable securities, and restricted cash at fair value. We classify our cash equivalents, marketable securities and restricted cash within Level 1 or Level 2 because we value these investments using quoted market prices or alternative pricing sources and models utilizing market observable inputs. The fair value of our Level 1 financial assets is based on quoted market prices of the identical underlying security. The fair value of our Level 2 financial assets is based on inputs that are directly or indirectly observable in the market, including the readily available pricing sources for the identical underlying security that may not be actively traded. Financial assets and liabilities measured and recorded at fair value on a recurring basis consisted of the following types of instruments: As of September 30, 2021 Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 132,880 $ — $ — $ 132,880 Certificate of deposit 200 — — 200 Municipal securities — 400 — 400 Total cash equivalents 133,080 400 — 133,480 Marketable securities: Corporate notes and bonds — 134,306 — 134,306 Commercial paper — 134,015 — 134,015 U.S. Treasury securities — 410,474 — 410,474 Municipal securities — 4,580 — 4,580 Asset-backed securities — 77,020 — 77,020 Foreign government and supranational securities — 30,384 — 30,384 Total marketable securities — 790,779 — 790,779 Restricted cash: Money market funds 893 893 Total restricted cash 893 — — 893 Total financial assets $ 134,373 $ 791,179 $ — $ 925,152 As of December 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 36,629 $ — $ — $ 36,629 Commercial paper — 4,998 — 4,998 Total cash equivalents 36,629 4,998 — 41,627 Marketable securities: Corporate notes and bonds — 14,314 — 14,314 Commercial paper — 41,445 — 41,445 U.S. Treasury securities — 95,972 — 95,972 Total marketable securities — 151,731 — 151,731 Restricted cash: Money market funds 980 — — 980 Total restricted cash 980 — — 980 Total financial assets $ 37,609 $ 156,729 $ — $ 194,338

Business Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2021
Business Combination and Asset Acquisition [Abstract]
Business Combinations	Business Combinations Signal Sciences On October 1, 2020, we completed the acquisition of Signal Sciences. We acquired 100% of the voting rights of Signal Sciences and it is now our wholly-owned subsidiary. The acquisition is expected to expand our security portfolio and bolster our existing security offerings with our web application and API protection solutions. Under the terms of the Merger Agreement, we acquired Signal Sciences for an aggregate purchase price of $759.4 million, consisting of approximately $223.0 million in cash and the balance in Class A Common Stock and equity consideration of $536.4 million. A total of 6,367,709 shares were issued, of which the fair value of 5,471,210 shares were attributed to purchase price and 896,499 shares, which are restricted as they are subject to revesting conditions, will be recognized as stock-based compensation expense as the required employee services are provided. These restricted shares, which belong to the three co-founders of Signal Sciences, will revest on a quarterly basis over a 2-year period. All of these shares have a par value of $0.00002 per share. As part of the acquisition, we assumed the Signal Sciences Corp. 2014 Stock Option and Grant Plan, as amended (the “Signal Plan”) and registered 251,754 shares under the Signal Plan, which were the outstanding unvested options to purchase shares of common stock of Signal Sciences. Such options became exercisable to purchase shares of Fastly’s Class A common stock, subject to appropriate adjustments to the number of shares and the exercise price of each such option. We assumed the aforementioned unvested options at the completion of the acquisition with an estimated fair value of $21.8 million. Of the total consideration, $1.1 million was allocated to the purchase price and $20.7 million was allocated to future services, which will be expensed over the employees' remaining requisite service periods of approximately 2.5 years on a straight-line basis. The estimated fair value of the stock options assumed was determined using the Black-Scholes option pricing model. The share conversion ratio of 0.1 was applied to convert Signal Sciences’ outstanding stock awards into shares of Fastly's Class A common stock. We accounted for the transaction as a business combination using the acquisition method of accounting. We allocated the purchase price to the tangible and identifiable intangible assets acquired and liabilities assumed based on their respective estimated fair values on the acquisition date. The acquired tangible assets acquired and liabilities assumed were recorded at their estimated fair values. The determination of the fair value of the intangible assets acquired required management to make significant estimates and assumptions related to forecasted future revenues and selection of the royalty rate and discount rate. The purchase consideration was allocated to the tangible and intangible assets and liabilities acquired as of the acquisition date, with the excess recorded to goodwill, which includes the value attributable to the assembled workforce, as shown below (in thousands): Amount Assets acquired Cash and cash equivalents $ 21,501 Other current assets 6,419 Intangible assets, net 124,100 Other non-current assets 8,094 Total assets acquired $ 160,114 Liabilities assumed Current liabilities (14,755) Non-current liabilities (21,170) Total liabilities assumed $ (35,925) Net assets acquired 124,189 Total acquisition consideration 759,393 Goodwill recorded $ 635,204 Identifiable finite-lived intangible assets were comprised of the following: Total (in thousands) Estimated useful life (in years) Customer relationships $ 69,100 8.0 Developed technology 49,500 5.0 Trade name 3,300 3.0 Backlog 2,200 2.0 Total intangible assets acquired $ 124,100 The fair values of the acquired developed technology and trade name intangible assets were determined using the relief from royalty method. The fair values of the acquired customer relationships and backlog intangible assets were determined using the multi-period excess earnings method. The acquired intangible assets have a total weighted average amortization period of 6.6 years. As part of the stock acquisition of Signal Sciences, we allocated a significant value of the acquisition to intangible assets. The deferred tax liability provided an additional source of taxable income to support the realization of the pre-existing deferred tax assets. As a result a portion of our valuation allowance was released and we recorded a $13.0 million tax benefit in the year ended December 31, 2020. During the year ended December 31, 2020, acquisition-related expenses of $20.8 million were expensed within general and administrative expenses as incurred. The amounts of revenue and net loss of Signal Sciences included in our consolidated statement of operations from the acquisition date of October 1, 2020 to December 31, 2020 are $6.7 million and $23.0 million, respectively. The unaudited pro forma results do not reflect any cost saving synergies from operating efficiencies, or the effect of the incremental costs incurred from integrating these companies. For pro forma purposes, 2020 earnings were adjusted to exclude acquisition-related costs. Accordingly, these unaudited pro forma results are presented for informational purposes only and are not necessarily indicative of what the actual results of operations of the combined company would have been if the acquisition had occurred at the beginning of the period presented, nor are they indicative of future results of operations. The unaudited pro forma financial information was as follows (in thousands): (Unaudited) For the year ended (in thousands) Revenue $ 313,665 Net loss $ (159,248)

Balance Sheet Information

Balance Sheet Information	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Information	Balance Sheet Information Property and equipment, net Property and equipment, net consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Computer and networking equipment $ 187,050 $ 129,998 Leasehold improvements 3,793 3,817 Furniture and fixtures 1,223 1,092 Office equipment 654 659 Internal-use software 35,316 22,066 Property and equipment, gross $ 228,036 $ 157,632 Accumulated depreciation and amortization (80,307) (61,653) Property and equipment, net $ 147,729 $ 95,979 Depreciation on property and equipment for the three months ended September 30, 2021 and 2020 was approximately $7.4 million and $4.9 million, respectively. Included in these amounts was amortization expense for capitalized internal-use software costs of approximately $1.3 million and $0.5 million, respectively, for the three months ended September 30, 2021 and 2020. Depreciation expense on property and equipment for the nine months ended September 30, 2021 and 2020 was approximately $20.7 million and $14.3 million, respectively. Included in these amounts was amortization expense for capitalized internal-use software costs of approximately $3.2 million and $1.7 million, respectively, for the nine months ended September 30, 2021 and 2020. We recorded out-of-period adjustments in the quarter ended September 30, 2021 to correct and capitalize certain internal-use software costs that were previously expensed of $5.1 million, of which $2.4 million and $2.7 million related to the quarterly periods ended March 31, 2021 and June 30, 2021, respectively. In the quarter ended March 31, 2021, $2.0 million and $0.4 million were previously recorded to research and development and cost of revenue, respectively. In the quarter ended June 30, 2021, $2.3 million and $0.4 million were previously recorded to research and development and cost of revenue, respectively. The out-of-period adjustments are considered quantitatively and qualitatively immaterial. As of September 30, 2021 and December 31, 2020, the unamortized balance of capitalized internal-use software costs on our Condensed Consolidated Balance Sheets was approximately $24.4 million and $14.2 million, respectively. We lease certain networking equipment from various third parties, through equipment finance leases. Our networking equipment assets as of September 30, 2021 and December 31, 2020, included a total of $56.8 million and $36.2 million acquired under finance lease agreements, respectively. These leases are capitalized in property and equipment, and the related amortization of assets under finance leases is included in depreciation and amortization expense. The accumulated depreciation of the associated networking equipment assets under finance leases totaled $13.0 million and $6.7 million as of September 30, 2021 and December 31, 2020, respectively. Other assets Other assets consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Deferred contract costs, net $ 23,067 $ 19,332 Restricted cash 893 893 Other assets 4,182 4,692 Total other assets $ 28,142 $ 24,917 Accrued expenses Accrued expenses consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Accrued compensation and related benefits $ 14,812 $ 17,840 Sales and use tax payable 7,486 6,274 Accrued acquisition-related costs — 3,644 Accrued colocation and bandwidth costs 7,231 2,208 Other accrued liabilities 6,534 4,368 Total accrued expenses $ 36,063 $ 34,334 Other Current Liabilities Other current liabilities consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Deferred revenue, current $ 21,631 $ 15,916 Accrued computer and networking equipment 2,274 3,126 Liability for early-exercised stock options 213 255 Other current liabilities 640 380 Total other current liabilities $ 24,758 $ 19,677 Other Long-Term Liabilities Other long-term liabilities consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Deferred revenue, non-current $ 3,186 $ 2,104 CARES Act payroll tax deferral 1,676 1,676 Other long-term liabilities 194 620 Total other long-term liabilities $ 5,056 $ 4,400

Leases

Leases	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Leases	Leases We have operating leases for corporate offices and data centers ("colocation leases"), and finance leases for networking equipment. Our leases have remaining lease terms of 0.1 years to 6 years, some of which include options to extend the leases. We have elected the short-term lease recognition practical expedient, whereby we will not recognize right-of-use ("ROU") assets or lease liabilities for existing short-term leases. We also sublease a portion of our corporate office spaces. Our subleases have remaining lease terms of 3 years. Our sublease income was $0.2 million and $0.3 million, respectively, for the three months ended September 30, 2021, and 2020. Our sublease income was $0.7 million and $0.9 million, respectively, for the nine months ended September 30, 2021, and 2020. The components of lease cost were as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Operating lease cost: Operating lease cost $ 7,018 $ 5,578 $ 19,741 $ 15,670 Variable lease cost 1,806 1,234 4,624 2,590 Total operating lease costs $ 8,824 $ 6,812 $ 24,365 $ 18,260 Finance lease cost: Amortization of assets under finance lease $ 4,124 $ 419 $ 6,608 $ 1,827 Interest 524 186 1,259 454 Total finance lease costs $ 4,648 $ 605 $ 7,867 $ 2,281 Other information related to leases was as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Supplemental Cash Flow Information Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases liabilities included in cash from operating activities $ 6,879 $ 4,439 $ 19,735 $ 12,852 Payments for finance leases interest included in cash from operating activities $ 524 $ 186 $ 1,259 $ 454 Payments for finance leases liabilities included in cash from financing activities $ 3,985 $ 1,001 $ 10,564 $ 3,901 Assets obtained in exchange for lease obligations: Operating leases $ 12,264 $ 4,817 $ 25,745 $ 15,095 Finance leases $ 12,861 $ 3,510 $ 28,399 $ 11,352 As of September 30, As of December 31, 2021 2020 Weighted Average Remaining Lease Term (in years) Operating leases 4.44 4.44 Finance leases 2.26 2.51 Weighted Average Discount Rate Operating leases 5.29 % 5.68 % Finance leases 4.92 % 5.12 % As of September 30, 2021, we had undiscounted commitments of $7.0 million for operating leases that have not yet commenced, and therefore are not included in the right-of-use asset or operating lease liability. These operating leases will commence in 2021 with lease terms of 1 year to 6 years. Future minimum lease payments under non-cancellable leases as of September 30, 2021 were as follows: Operating Leases Finance Leases (in thousands) Remainder of 2021 $ 7,108 $ 5,268 2022 24,241 19,414 2023 17,710 15,930 2024 13,337 4,788 2025 12,395 — Thereafter 17,208 — Total future minimum lease payments $ 91,999 $ 45,400 Less: imputed interest (9,943) (2,062) Total liability $ 82,056 $ 43,338
Leases	Leases We have operating leases for corporate offices and data centers ("colocation leases"), and finance leases for networking equipment. Our leases have remaining lease terms of 0.1 years to 6 years, some of which include options to extend the leases. We have elected the short-term lease recognition practical expedient, whereby we will not recognize right-of-use ("ROU") assets or lease liabilities for existing short-term leases. We also sublease a portion of our corporate office spaces. Our subleases have remaining lease terms of 3 years. Our sublease income was $0.2 million and $0.3 million, respectively, for the three months ended September 30, 2021, and 2020. Our sublease income was $0.7 million and $0.9 million, respectively, for the nine months ended September 30, 2021, and 2020. The components of lease cost were as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Operating lease cost: Operating lease cost $ 7,018 $ 5,578 $ 19,741 $ 15,670 Variable lease cost 1,806 1,234 4,624 2,590 Total operating lease costs $ 8,824 $ 6,812 $ 24,365 $ 18,260 Finance lease cost: Amortization of assets under finance lease $ 4,124 $ 419 $ 6,608 $ 1,827 Interest 524 186 1,259 454 Total finance lease costs $ 4,648 $ 605 $ 7,867 $ 2,281 Other information related to leases was as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Supplemental Cash Flow Information Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases liabilities included in cash from operating activities $ 6,879 $ 4,439 $ 19,735 $ 12,852 Payments for finance leases interest included in cash from operating activities $ 524 $ 186 $ 1,259 $ 454 Payments for finance leases liabilities included in cash from financing activities $ 3,985 $ 1,001 $ 10,564 $ 3,901 Assets obtained in exchange for lease obligations: Operating leases $ 12,264 $ 4,817 $ 25,745 $ 15,095 Finance leases $ 12,861 $ 3,510 $ 28,399 $ 11,352 As of September 30, As of December 31, 2021 2020 Weighted Average Remaining Lease Term (in years) Operating leases 4.44 4.44 Finance leases 2.26 2.51 Weighted Average Discount Rate Operating leases 5.29 % 5.68 % Finance leases 4.92 % 5.12 % As of September 30, 2021, we had undiscounted commitments of $7.0 million for operating leases that have not yet commenced, and therefore are not included in the right-of-use asset or operating lease liability. These operating leases will commence in 2021 with lease terms of 1 year to 6 years. Future minimum lease payments under non-cancellable leases as of September 30, 2021 were as follows: Operating Leases Finance Leases (in thousands) Remainder of 2021 $ 7,108 $ 5,268 2022 24,241 19,414 2023 17,710 15,930 2024 13,337 4,788 2025 12,395 — Thereafter 17,208 — Total future minimum lease payments $ 91,999 $ 45,400 Less: imputed interest (9,943) (2,062) Total liability $ 82,056 $ 43,338

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets The changes in the carrying amount of goodwill for the nine months ended September 30, 2021 are as follows: Nine months ended September 30, 2021 (in thousands) Balance as of December 31, 2020 $ 635,590 Foreign currency translation and other adjustments 45 Balance as of September 30, 2021 $ 635,635 As of September 30, 2021 and December 31, 2020, our intangible assets consisted of the following: As of September 30, 2021 As of December 31, 2020 Gross carrying value Accumulated amortization Net carrying value Gross carrying value Accumulated amortization Net carrying value (in thousands) Intangible assets: Customer relationships $ 69,100 $ (8,638) $ 60,462 $ 69,100 $ (2,053) $ 67,047 Developed technology 49,500 (9,900) 39,600 49,500 (2,475) 47,025 Trade names 3,300 (1,100) 2,200 3,300 (275) 3,025 Internet protocol addresses 4,984 (848) 4,136 2,891 (578) 2,313 Backlog 2,200 (1,100) 1,100 2,200 (275) 1,925 In-process research and development ("IPR&D") 368 — 368 368 — 368 Domain name 39 — 39 39 — 39 Total intangible assets $ 129,491 $ (21,586) $ 107,905 $ 127,398 $ (5,656) $ 121,742 Our intangible assets are comprised of customer relationships, developed technology, trade names, internet protocol addresses, backlog, and IPR&D. Our customer relationships, developed technology, trade names, internet protocol addresses, backlog, domain name intangible assets are subject to amortization. IPR&D intangible and domain name assets are indefinite-lived and not subject to amortization. We purchased $2.1 million and $1.8 million of intangible assets during the nine months ended September 30, 2021 and 2020, respectively. We did not purchase intangible assets during the three months ended September 30, 2021 and 2020. Amortization expense was $5.3 million and $15.9 million for the three and nine months ended September 30, 2021, respectively. Amortization expense was less than $0.1 million and $0.1 million for the three and nine months ended September 30, 2020, respectively. We perform tests for impairment of goodwill and long-lived assets on an annual basis as of October 31 or more frequently if events or changes in circumstances indicate that our long-lived assets might be impaired. We did not record any impairment charges during both the three and nine months ended September 30, 2021 and 2020. The annual expected amortization expense of intangible assets subject to amortization as of September 30, 2021 is as follows: As of September 30, 2021 (in thousands) Remainder of 2021 $ 5,313 2022 20,974 2023 19,874 2024 19,040 2025 16,561 Thereafter 25,771 Total $ 107,533

Debt Instruments

Debt Instruments	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Debt Instruments	Debt Instruments Cash Collateralized Revolving Credit Agreement In November 2019, we entered into a Revolving Credit Agreement with Citibank, N.A (the "Lender") for an aggregate commitment amount of $70.0 million with a maturity date of November 3, 2022 (the "Revolver"). The amount of borrowings available under the Revolving Credit Agreement at any time are collateralized by our cash, which is classified as restricted cash on our balance sheets. With prior written notice to the Lender, we have the right, at any time prior to the Revolver's maturity date, without premium or penalty, to terminate or reduce the Revolver arrangement. In event of such termination, the aggregate principal of the then outstanding amounts, including any accrued interest to date, shall be repaid and the restrictions on the associated collateralized cash would be released. The interest rate associated with each advance under the Revolving Credit Agreement is equal to the sum of LIBOR for the applicable interest period plus 1.50% which is a per annum rate based on outstanding borrowings. As such, for the initial interest period ending in November 2020, the interest rate is set at 3.46%. The commitment fee is 0.20% per annum based on the average daily unused amount of the commitment amount. Interest payments on outstanding borrowings are due on the last day of each interest period and payments for the commitment fee are due at the end of each calendar quarter. In November 2020, we terminated the Revolving Credit Agreement in accordance with its terms. In connection with the termination of the Revolving Credit Agreement, we repaid the then outstanding aggregate principal amount of $20.3 million, as well as any accrued and unpaid interest, as of the termination date. The associated restriction on the collateralized cash of $70.1 million was also released, accordingly. Senior Secured Credit Facilities Agreement On February 16, 2021, we entered into a Senior Secured Credit Facilities Agreement ("Credit Agreement") with Silicon Valley Bank for an aggregate commitment amount of $100.0 million with a maturity date of February 16, 2024. The Credit Agreement bears interest at a rate per annum equal to the sum of LIBOR for the applicable interest period plus 1.75% - 2.00%, depending on the average daily outstanding balance of all loans and letters of credit under the Credit Agreement. Interest payments on outstanding borrowings are due on the last day of each interest period. The Credit Agreement has a commitment fee on the unused portion of the borrowing commitment, which is payable on the last day of each calendar quarter at a rate per annum of 0.20% - 0.25% depending on the average daily outstanding balance of all loans and letters of credit under the Credit Agreement. In addition, our Credit Agreement contains a financial covenant that requires us to maintain a consolidated adjusted quick ratio of at least 1:25 to 1:00 tested on a quarterly basis as well as a springing revenue growth covenant for certain periods if our consolidated adjusted quick ratio falls below 1.75 to 1:00 on the last day of any fiscal quarter. The Credit Agreement requires us to comply with these affirmative and negative covenants and we were in compliance with all covenants as of September 30, 2021. We recorded $0.6 million of debt issuance costs associated with the Credit Agreement in other assets on our condensed consolidated balance sheet. During the three and nine months ended September 30, 2021, no amount was drawn down on our Credit Agreement. As of September 30, 2021, and no amount was outstanding under the Credit Agreement. Convertible Senior Notes On March 5, 2021, we issued approximately $948.8 million aggregate principal amount of our 0% convertible senior notes due 2026 (the “Notes”), including the exercise in full by the initial purchasers of their option to purchase up to an additional approximately $123.8 million principal amount of the Notes. The Notes were issued in a private placement to qualified institutional buyers pursuant to Rule144A under the Securities Act. The Notes will mature on March 15, 2026, unless earlier converted, redeemed or repurchased. The net proceeds from the issuance of the Notes were approximately $930.0 million after deducting the initial purchasers’ discounts and transaction costs. We may not redeem the Notes prior to March 20, 2024. On or after March 20, 2024, we may redeem for cash, all or any portion of the Notes, at our option, at a redemption price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid special interest, if any, to, but excluding, the redemption date, if the last reported sale price of our common stock has been at least 130% of the conversion price for the Notes then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending on, and including, the trading day immediately preceding the date on which we provide notice of redemption. No sinking fund is provided for the Notes. Holders of the Notes may convert their notes at their option at any time prior to the close of business on the business day immediately preceding December 15, 2025, only under the following circumstances: (i) during any calendar quarter commencing after the calendar quarter ending on June 30, 2021 (and only during such calendar quarter), if the last reported sale price of our Class A common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price for the Notes on each applicable trading day; (ii) during the five business day period after any ten consecutive trading day period (the “Measurement Period”) in which the trading price, as defined in the indenture agreement governing the Note filed with our Current Report on Form 8-K filed with the Securities and Exchange Commission on March 5, 2021, per $1,000 principal amount of notes for each trading day of the Measurement Period was less than 98% of the product of the last reported sale price of our Class A common stock and the conversion rate on each such trading day; (iii) if we call such Notes for redemption, at any time prior to the close of business on the scheduled trading day immediately preceding the applicable redemption date, but only with respect to the Notes called (or deemed called) for redemption; or (iv) upon the occurrence of specified corporate events. On or after December 15, 2025 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert all or any portion of their notes at any time, regardless of the foregoing circumstances. Upon conversion, we may satisfy our conversion obligation by paying or delivering, as the case may be, cash, shares of our Class A common stock or a combination of cash and shares of our Class A common stock, at our election. The initial conversion rate is 9.7272 shares of Class A common stock per $1,000 principal amount of Notes, equivalent to an initial conversion price of approximately $102.80 per share of Class A common stock. The conversion rate is subject to adjustment as described in the indenture governing the Notes but will not be adjusted for any accrued and unpaid special interest. In addition, following certain corporate events that occur prior to the maturity date of the Notes or if we deliver a notice of redemption in respect of the Notes, we will, in certain circumstances, increase the conversion rate of the Notes for a holder who elects to convert its Notes, in connection with such a corporate event or convert its Notes called (or deemed called) for redemption during the related redemption period, as the case may be. The indenture includes customary covenants and sets forth certain events of default after which the Notes may be declared immediately due and payable and sets forth certain types of bankruptcy or insolvency events of default involving us after which the Notes become automatically due and payable. If we undergo a fundamental change, as defined in the indenture agreement governing the Notes, then subject to certain conditions and except as described in the indenture governing the Notes, holders may require us to repurchase for cash all or any portion of their Notes at a fundamental change repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid special interest, if any, to, but excluding, the fundamental change repurchase date. We evaluated the terms of our debt and concluded that the instrument does not require separation and that there were no other derivatives that required separation. As such, we have combined these features with the host contract and we account for our convertible debt as a single liability in long-term debt on our condensed consolidated balance sheet. The initial purchasers' discounts and transaction costs of $18.6 million incurred related to the issuance of the Notes were classified as liability and represents the difference between the principal amount of the Notes and the liability component (the “debt discount”), which is amortized to interest expense using the effective interest method over the term of the Notes. As of September 30, 2021, the conversion conditions have not been met and therefore the Notes are not yet convertible. The following table reflects the carrying values of the debt agreements as of September 30, 2021: As of September 30, 2021 (in thousands) Convertible Senior notes (effective interest rate of 0.40%) Principal amount $ 948,750 Less: unamortized debt issuance costs (16,445) Less: current portion of long-term debt — Long-term debt, less current portion $ 932,305

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Purchase Commitments As of September 30, 2021, we had long-term commitments for cost of revenue related agreements (i.e., bandwidth usage, peering and other managed services with various networks, internet service providers ("ISPs") and other third-party vendors). We also have long-term commitments for various non-cancelable software as a service ("SaaS") agreements. Our minimum future commitments related to our purchase commitments as of September 30, 2021 were as follows: Cost of Revenue Commitments SaaS Agreements Total Purchase Commitments (in thousands) Remainder of 2021 $ 13,468 $ 4,381 $ 17,849 2022 27,771 14,590 42,361 2023 5,502 12,814 18,316 2024 2,920 140 3,060 2025 160 — 160 Thereafter 46 — 46 Total $ 49,867 $ 31,925 $ 81,792 Sales and Use Tax We conduct operations in many tax jurisdictions throughout the United States. In many of these jurisdictions, non-income-based taxes, such as sales and use and telecommunications taxes are assessed on our operations. We are subject to indirect taxes, and may be subject to certain other taxes, in some of these jurisdictions. Historically, we have not billed or collected these taxes and, in accordance with U.S. GAAP, we have recorded a provision for our tax exposure in these jurisdictions when it is both probable that a liability has been incurred and the amount of the exposure can be reasonably estimated. As a result, we have recorded a liability of $7.5 million and $6.3 million as of September 30, 2021 and December 31, 2020, respectively. These estimates are based on several key assumptions, including the taxability of our products, the jurisdictions in which we believe we have nexus and the sourcing of revenues to those jurisdictions. In the event these jurisdictions challenge our assumptions and analysis, our actual exposure could differ materially from our current estimates. Legal Matters We are currently involved in, and may in the future be involved in, various legal proceedings and claims arising from the normal course of business, and an unfavorable resolution of any of these matters could materially affect our future results of operations, cash flows or financial position. We are also party to various disputes that management considers routine and incidental to its business. Management does not expect the results of any of these routine actions to have a material effect on our business, results of operations, financial condition, or cash flows. On August 27, 2020, a purported securities class action lawsuit was filed in the United States District Court for the Northern District of California, captioned Marcos Betancourt v. Fastly, Inc., et al. (Case No. 4:20-cv-06024-PJH) naming as defendants us and certain of our officers. On September 15, 2020, a substantively identical complaint was filed against the same defendants in the same court, captioned Rami Habib v. Fastly, Inc., et al. (Case No. 4:20-cv-06454-JST). On September 27, 2020, the court consolidated the two cases into one putative class action, captioned In re Fastly, Inc. Securities Litigation. On February 10, 2021, the Court appointed lead plaintiff (“Lead Plaintiff”) and lead counsel. On April 12, 2021, Lead Plaintiff filed a consolidated complaint (the “Consolidated Complaint”). The Consolidated Complaint asserts that all defendants violated Section 10(b) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and SEC Rule 10b-5 by making materially false or misleading statements between May 6, 2020 and October 14, 2020 regarding the Company’s business and financials, including allegations that the Company failed to disclose the identity of one of its largest customers. The Lead Plaintiff also alleges that certain of the Company’s officers violated Section 20(a) of the Exchange Act. On June 11, 2021, defendants filed a motion to dismiss the Consolidated Complaint that Lead Plaintiff opposed on July 26, 2021, and defendants filed a reply on September 1, 2021. The Court held a hearing on the motion to dismiss on November 4, 2021. The Company is awaiting a decision on the motion to dismiss. On December 28, 2020, certain of our officers and directors were named as defendants in a shareholder derivative action filed in the United States District Court for the District of Delaware, captioned Wei v. Bixby, et al., Case No. 1:20-cv-01773-MN. On February 2, 2021, a substantially similar shareholder derivative complaint was filed against the same defendants in the same court, captioned Kristen Gorenberg v. Bixby et al., Case No. 1:21-cv-00136. The derivative complaints assert, inter alia, breach of fiduciary duty claims. On March 15, 2021, the Court consolidated the cases and stayed the consolidated derivative action until after resolution of our motion to dismiss in the above-referenced securities class action. It is possible that additional lawsuits will be filed, or allegations made by stockholders, regarding these same or other matters and also naming as defendants the Company and our officers and directors. The pending lawsuits and any other related lawsuits are subject to inherent uncertainties, and the actual defense and disposition costs will depend upon many unknown factors. The outcome of the pending lawsuits and any other related lawsuits is necessarily uncertain. We could be forced to expend significant resources in the defense of the pending lawsuits and any additional lawsuits, and we may not prevail. In addition, we may incur substantial legal fees and costs in connection with such lawsuits. We currently are not able to estimate the possible cost to us from these matters, as the pending lawsuits are currently at an early stage, and we cannot be certain how long it may take to resolve the pending lawsuits or the possible amount of any damages that we may be required to pay. Such amounts could be material to our financial statements if we do not prevail in the defense against the pending lawsuits and any other related lawsuits, or even if we do prevail. As of September 30, 2021, we have not accrued for any loss contingencies on the above mentioned lawsuits as we do not believe an outcome resulting in a loss is probable. We will accrue for loss contingencies if it becomes both probable that we will incur a loss and if we can reasonably estimate the amount or range of the loss. Indemnification We enter into standard indemnification agreements in the ordinary course of business. Pursuant to these agreements, we agree to indemnify, hold harmless, and reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally our business partners or customers, in connection with our provision of its services. Generally, these obligations are limited to claims relating to infringement of a patent, copyright, or other intellectual property right, breach of our security or data protection obligations, or our negligence, willful misconduct, or violation of law. Subject to applicable statutes of limitation, the term of these indemnification agreements is generally for the duration of the agreement. The maximum potential amount of future payments we could be required to make under these indemnification agreements is unlimited; however, we carry insurance that covers certain third-party claims relating to our services and could limit our exposure in that respect. We have agreed to indemnify each of our officers and directors during his or her lifetime for certain events or occurrences that happen by reason of the fact that the officer or director is, was, or has agreed to serve as an officer or director of the Company. We have director and officer insurance policies that may limit our exposure and may enable us to recover a portion of certain future amounts paid. To date, we have not encountered material costs as a result of such indemnification obligations and have not accrued any related liabilities in our financial statements. In assessing whether to establish an accrual, we consider such factors as the degree of probability of an unfavorable outcome and the ability to make a reasonable estimate of the amount of loss.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders' Equity Common Stock Our Amended and Restated Certificate of Incorporation, as amended and restated in May 2019 (the "Certificate"), authorizes the issuance of 1.0 billion shares of Class A common stock and 94.1 million shares of Class B common stock, each at a par value per share of $0.00002. Holders of Class A common stock are entitled to one vote per share and holders of Class B common stock are entitled to 10 votes per share. As of September 30, 2021 and December 31, 2020, 117.2 million and 103.4 million shares of Class A common stock were issued and outstanding, respectively. As of September 30, 2021 and December 31, 2020, 0.0 million and 10.2 million shares of Class B common stock were issued and outstanding, respectively. Our Certificate includes an automatic conversion provision, which, on the date when the outstanding shares of our Class B common stock represent less than 10% of the aggregate number of shares of the then outstanding Class A common stock and Class B common stock (the “Sunset Trigger Date”), all our outstanding shares of Class B common stock will automatically convert into the same number of shares of Class A common stock under the terms of our Certificate on the trading day falling nine months after the Sunset Trigger Date ("the Conversion"). No additional Class B shares may be issued following the Conversion. On October 12, 2020, the outstanding shares of our Class B common stock represented less than 10% of the aggregate number of shares of the then outstanding Class A common stock and Class B common stock. As a result, all our outstanding shares of Class B common stock automatically converted into the same number of shares of Class A common stock on July 12, 2021 (the "Conversion"), pursuant to the terms of our Certificate. Upon the conversion, outstanding options denominated in shares of Class B common stock issued under any of the Company’s equity incentive plans remained unchanged, except that they now represent the right to receive shares of Class A common stock. In accordance with our Certificate, the shares of Class B common stock that converted to Class A common stock were retired and will not be reissued by us. On July 12, 2021, we filed a certificate with the Secretary of State of the State of Delaware effecting the retirement of the shares of Class B common stock that were issued but no longer outstanding following the Conversion. Upon the effectiveness of the certificate, our total number of authorized shares of capital stock was reduced by the retirement of 90.0 million shares of Class B common stock. Preferred Stock Our Certificate also authorizes the issuance of 10.0 million shares of preferred stock, at a par value per share of $0.00002, with rights and preferences, including voting rights, designated from time to time by the Board of Directors (the "Board"). As of both September 30, 2021 and December 31, 2020, no shares of preferred stock were issued and outstanding. Equity Incentive Plans In March 2011, our stockholders approved our 2011 Equity Incentive Plan ("2011 Plan") which allows for the issuance of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, and restricted stock unit awards ("RSUs") to employees, directors, and consultants of the Company. Options granted under our 2011 Plan were originally exercisable for shares of our Class B common stock, but due to the Conversion, these awards are now exercisable for shares of our Class A common stock. As of December 31, 2020, there were 23.6 million shares of Class B common stock reserved for issuance pursuant to outstanding stock options under the 2011 Plan. As of December 31, 2020, there were no shares of Class B common stock available for issuance for future grants under the 2011 Plan. All such shares of Class B common stock were converted to Class A common stock in July 2021 pursuant to the Conversion. As of September 30, 2021, there were 23.6 million shares of Class A common stock reserved for issuance pursuant to outstanding stock options under the 2011 Plan. As of September 30, 2021 there were no shares of Class A common stock available for issuance for future grants under the 2011 Plan. In May 2019, in conjunction with our IPO, our Board and stockholders approved our 2019 Equity Incentive Plan (the "2019 Plan") which allows for the issuance of incentive stock options, non-statutory stock options, stock appreciation rights, RSUs, performance-based stock awards, and other forms of equity compensation, which are collectively referred to as stock awards. Additionally, the 2019 Plan provides for the grant of performance cash awards. Options are exercisable for shares of our Class A common stock. No further awards will be issued under the 2011 Plan. In October 2020, we assumed the Signal Sciences Corp. 2014 Stock Option and Grant Plan, as amended (the “Signal Plan”) and registered 251,754 shares under the Signal Plan, which were the outstanding unvested options to purchase shares of common stock of Signal Sciences. Such options became exercisable to purchase shares of our Class A common stock, subject to appropriate adjustments to the number of shares and the exercise price of each such option. As of September 30, 2021 and December 31, 2020, an aggregate of 25.1 million shares and 19.4 million shares of Class A common stock have been reserved for issuance under the 2019 Plan, respectively. As of September 30, 2021 and December 31, 2020, there were 17.1 million and 12.8 million Class A common stock available for issuance under the 2019 Plan, respectively. In May 2019, in conjunction with our IPO, our Board and stockholders approved the Employee Stock Purchase Plan ("ESPP"). The ESPP allows eligible employees to purchase shares of our Class A common stock through payroll deductions of up to 15% of their eligible compensation, subject to a maximum of $25,000 per calendar year. As of September 30, 2021 and December 31, 2020, an aggregate of 4.6 million shares and 3.5 million shares of Class A common stock have been reserved for issuance under the ESPP, respectively. As of September 30, 2021 and December 31, 2020, there we re 3.8 million shares and 2.8 million shares of Class A common stock available for future issuance under the ESPP, respectively. Stock Options Options granted under the 2011 Plan are exercisable for Class B common stock and generally expire within 10 years from the date of grant and generally vest over four years, at the rate of 25% on the first anniversary of the date of grant and ratably on a monthly basis over the remaining 36-month period thereafter based on continued service. Due to the Conversion, options granted under the 2011 Plan are now exercisable for Class A common stock. Options granted under the 2019 Plan are exercisable for Class A common stock and generally expire within 10 years from the date of grant and generally vest over four years, at the rate of 25% on the first anniversary of the date of grant and ratably on a monthly basis over the remaining 36-month period thereafter based on continued service. Forfeitures are recognized as they occur. The following table summarizes stock option activity during the nine months ended September 30, 2021: Shares Weighted- Weighted- Aggregate (in thousands) (in years) (in thousands) Outstanding at December 31, 2020 6,963 $ 5.63 6.7 $ 569,094 Granted — — Exercised (1,527) 5.96 Cancelled/forfeited (261) 11.00 Outstanding at September 30, 2021 5,175 $ 5.27 5.2 $ 182,027 Vested and exercisable at September 30, 2021 3,912 $ 3.97 4.6 $ 142,675 Unvested and exercisable at September 30, 2021 173 $ 6.65 7.1 $ 5,841 The total pre-tax intrinsic value of options exercised during the nine months ended September 30, 2021 and 2020 was $52.6 million and $157.9 million, respectively. The total grant date fair value of employee options vested for the nine months ended September 30, 2021 and 2020 was $8.3 million and $6.5 million, respectively. There were no options granted during the three and nine months ended September 30, 2021 and 2020. During the three and nine months ended September 30, 2021, we recorded stock-based compensation expense from stock options of approximately $5.3 million and $13.4 million, respectively. During the three and nine months ended September 30, 2020, we recorded stock-based compensation expense from stock options of approximately $1.8 million and $5.7 million, respectively. During the three and nine months ended September 30, 2021, we modified the terms of options awarded to certain employees to allow for the remaining unvested awards to be fully vested upon their change in employment status. As a result, we recorded stock-based compensation expense of $2.4 million and $3.7 million during three and nine months ended September 30, 2021, respectively, in relation to such modifications. Included in the expense for the three and nine months ended September 30, 2021 are incremental fair value adjustments of $2.1 million and $3.3 million, respectively. During the three and nine months ended September 30, 2020, we recorded stock-based compensation expense of $0.4 million in both the three and nine months ended September 30, 2020 in relation to modifications. Included in this expense is the incremental fair value adjustment of $0.3 million. As of September 30, 2021, total unrecognized stock-based compensation cost related to outstanding unvested stock options that are expected to vest was $14.5 million. This unrecognized stock-based compensation cost is expected to be recognized over a weighted-average period of approximately 1.23 years. Early Exercise of Stock Options Certain stock options granted by the Company are exercisable at the date of grant, with unvested shares subject to repurchase by the Company in the event of voluntary or involuntary termination of employment of the stockholder. Such exercises are recorded as a liability on the accompanying Condensed Consolidated Balance Sheets and reclassified into equity as the options vest. As of September 30, 2021 and December 31, 2020, a total of 47,882 and 90,977 shares of Class B Common Stock were subject to repurchase by the Company at the lower of (i) the fair market value of such shares on the date of repurchase, or (ii) the original exercise price of such shares. Due to the Conversion, these shares have been converted to Class A common stock. The corresponding exercise value of approximately $0.2 million and $0.4 million as of September 30, 2021 and December 31, 2020, respectively, is recorded in other current liabilities as of September 30, 2021 and other current liabilities and other long-term liabilities as of December 31, 2021 on the accompanying Condensed Consolidated Balance Sheets. The activity of non-vested shares as a result of early exercise of options granted to employees and non-employees, is as follows: Nine months ended September 30, 2021 (in thousands) Beginning balance as of December 31, 2020 91 Early exercise of options — Vested (43) Repurchased — Ending balance as of September 30, 2021 48 Restricted Stock Units ("RSUs") We began granting RSUs under the 2019 Plan during the fiscal year ended December 31, 2019. The fair value of RSUs is based on the grant date fair value and is expensed on a straight-line basis over the applicable vesting period. RSUs granted to new hires typically vest over four years, at the rate of 25% on the first anniversary of the vest date and ratably on a quarterly basis over the remaining 36-month period thereafter. RSUs granted to existing employees typically vest in equal quarterly installments over a four year service period. All vesting is contingent on continued service. Forfeitures are recognized as they occur. The following table summarizes RSU activity during the nine months ended September 30, 2021: Number of Shares Weighted-Average (in thousands) Unvested RSUs as of December 31, 2020 4,520 $ 30.01 Granted 1,890 63.95 Vested (1,463) 33.52 Cancelled/forfeited (470) 42.78 Unvested RSUs as of September 30, 2021 4,477 $ 41.85 During the three and nine months ended September 30, 2021, we recognized stock-based compensation expense related to RSUs of $23.0 million and $52.0 million, respectively. During the three and nine months ended September 30, 2020, we recognized stock-based compensation expense related to RSUs of $10.6 million and $28.0 million, respectively. During the three and nine months ended September 30, 2021, we modified the terms of its RSUs awarded to an employee to allow for the certain unvested awards to be fully vested upon their change in employment status. As a result,we recorded incremental stock-based compensation expense in relation to the modification of $3.9 million in both the three and nine months ended September 30, 2021. During the nine months ended September 30, 2020, we modified the terms of its RSUs awarded to an employee to allow for the remaining unvested awards to be fully vested upon their change in employment status. As a result, we recorded incremental stock-based compensation expense in relation to the modification of $4.8 million for the nine months ended September 30, 2020. During the three months ended September 30, 2020, incremental expense related to modifications were insignificant. As of September 30, 2021, total unrecognized stock-based compensation cost related to non-vested RSUs was $176.6 million. This unrecognized stock-based compensation cost is expected to be recognized over a weighted-average period of approximately 2.7 years. Stock Subject to Revest ("Revest Shares") In conjunction with the acquisition of Signal Sciences in fiscal 2020, a restriction was placed on 896,499 shares belonging to the three co-founders of Signal Sciences which are subject to revesting on a quarterly basis over a 2 year period. Refer to Note 5—Business Combinations for further details. The following table summarizes the activity related to the revest shares during the nine months ended September 30, 2021: Number of Shares Weighted-Average (in thousands) Unvested revest shares as of December 31, 2020 784 $ 97.84 Vested (336) 97.84 Cancelled/forfeited — Unvested revest shares as of September 30, 2021 448 $ 97.84 For the three and nine months ended September 30, 2021, we recognized stock-based compensation expense related to revest shares of $11.0 million and $32.9 million, respectively. As of September 30, 2021, total unrecognized stock-based compensation cost related to revest shares was $43.9 million. This unrecognized stock-based compensation cost is expected to be recognized over a weighted-average period of approximately 1 year. Performance-Based Restricted Stock Units ("PSUs") In March 2020, we granted a maximum total of 87,918 shares of PSUs to certain employees of the Company, pursuant to the Company's 2019 Equity Incentive Plan. The PSUs granted reflect a maximum of 200% of target performance and represent the right of the employees to be issued on a future date, one (1) share of Class A common stock for each RSU received that will vest on the applicable vesting date. On November 2, 2020, the Compensation Committee of the Board of Directors set the performance conditions related to the previously granted PSUs. The performance conditions are based on the level of achievement of certain Company and individual targets related to Fastly's operating plan for the fiscal year 2020 ("2020 operating plan"). The PSUs would vest at 50% of the target if the Company achieves 90% performance under the 2020 operating plan, 100% of the target if the Company achieves 100% performance under the 2020 operating plan and 200% of the target if the Company achieves 110% performance or greater under the 2020 operating plan. These awards were eligible to vest linearly within those parameters. Subject to employees’ continuous service with the Company through each vesting date, based on the extent of such targets achieved, 25% of the number of PSUs credited to them upon certification of achievement will vest on February 15, 2021, May 15, 2021, August 15, 2021, and November 15, 2021, respectively. Based on the results of the 2020 operating plan, the actual award was reduced to 75,828 shares which represents attainment of 172%. As a result, 12,090 shares subject to the PSUs were cancelled. In February 2021, we granted a maximum total of 70,680 shares of PSUs to certain employees of the Company, pursuant to the Company’s 2019 Equity Incentive Plan. The PSUs granted reflect a maximum of 150% of target performance and represent the right of the employees to be issued on a future date, one (1) share of Class A common stock for each RSU received that will vest on the applicable vesting date. The performance conditions were set and approved on the date of grant and are based on the level of achievement of certain Company and individual targets related to Fastly's operating plan for the fiscal year 2021 ("2021 operating plan"). The PSUs will vest at 50% of the target if the Company achieves 90% performance under the 2021 operating plan, 100% of the target if the Company achieves 100% performance under the 2021 operating plan and 150% of the target if the Company achieves 110% performance or greater under the 2021 operating plan. These awards will be eligible to vest linearly within those parameters. Subject to employees’ continuous service with the Company through each vesting date, based on the expected extent of such targets achieved, 25% of the total RSUs on February 15, 2022 and thereafter in 12 equal quarterly installments (i.e. 6.25% of the total RSUs will vest per quarter) on May 15, August 15, November 15, and February 15. The following table summarizes the activity related to the PSUs during the nine months ended September 30, 2021: Number of Shares Weighted-Average (in thousands) Unvested PSUs as of December 31, 2020 88 $ 65.11 Granted 71 102.06 Vested (57) 44.25 Cancelled/forfeited (12) 44.25 Unvested PSUs as of September 30, 2021 90 $ 110.29 For the three and nine months ended September 30, 2021, we recognized stock-based compensation expense (benefit) related to these PSUs of $-0.5 million and $3.8 million, respectively, based on the extent of the performance conditions that were deemed probable of achievement. As of the three and nine months ended September 30, 2020, we did not recognize any stock-based compensation expense related to these PSUs. As of September 30, 2021, total unrecognized stock-based compensation cost related to PSUs was $4.7 million. This unrecognized stock-based compensation cost is expected to be recognized over a weighted-average period of approximately 2.7 years. ESPP The ESPP allows eligible employees to purchase shares of our common stock through payroll deductions of up to 15% of their eligible compensation. The ESPP provides for six-month offering periods, commencing in May and November of each year. At the end of each offering period employees are able to purchase shares at 85% of the lower of the fair market value of our common stock on the first trading day of the offering period or on the date of purchase. We estimate the fair value of shares to be issued under the ESPP on the first day of the offering period using the Black-Scholes valuation model. The inputs to the Black-Scholes option pricing model are our stock price on the first date of the offering period, the risk-free interest rate, the estimated volatility of our stock price over the term of the offering period, the expected term of the offering period and the expected dividend rate. Stock-based compensation expense related to the ESPP is recognized on a straight-line basis over the offering period. Forfeitures are recognized as they occur. We estimated the fair value of shares granted under the ESPP using the Black-Scholes option pricing model with the following assumptions: Nine months ended September 30, 2021 2020 Fair value of common stock $12.66 - $24.07 $6.02 - 14.09 Expected term (in years) 0.49 to 0.50 0.50 Risk-free interest rate 0.02% - 0.10% 0.14% - 1.59% Expected volatility 47% - 50% 43% - 60% Dividend yield —% —% During the three and nine months ended September 30, 2021, we withheld $3.5 million and $6.0 million in contributions from employees, respectively, and recognized $0.6 million and $2.7 million in stock-based compensation expense related to the ESPP, respectively. During the three and nine months ended September 30, 2020, we withheld $2.0 million and $6.1 million in contributions from employees, respectively, and recognized $0.4 million and $2.3 million in stock-based compensation expense related to the ESPP, respectively. During the nine months ended September 30, 2021, 0.2 million shares of our Class A common stock was purchased under the offering period that commenced on November 21, 2020. During the nine months ended September 30, 2020, $0.2 million shares of our Class A common stock was purchased under the offering period that commenced on November 21, 2019. No common stock was issued under the ESPP in the three months ended September 30, 2021 or September 30, 2020. Stock-based Compensation Expense The following table summarizes the components of total stock-based compensation expense included in the accompanying Condensed Consolidated Statements of Operations: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Stock-based compensation expense by caption: Cost of revenue $ 1,897 $ 929 $ 4,911 $ 2,634 Research and development 14,752 4,371 31,344 10,095 Sales and marketing 9,121 3,194 19,760 11,753 General and administrative 10,866 3,648 44,885 10,270 Total $ 36,636 $ 12,142 $ 100,900 $ 34,752 For the three and nine months ended September 30, 2021, we capitalized $2.6 million and $3.4 million of stock-based compensation expense, respectively. For the three and nine months ended September 30, 2020, we capitalized $0.6 million and $1.2 million of stock-based compensation expense, respectively. Common Stock Warrant Liabilities Prior to the IPO, we issued convertible preferred stock warrants in conjunction with the issuances of debt. We recorded these warrants to purchase convertible preferred stock as a liability on the consolidated balance sheets at fair value upon issuance as the warrants were exercisable for contingently redeemable preferred stock which was classified outside of stockholders' equity (deficit). The liability associated with these warrants were subject to remeasurement at each balance sheet date, with changes in fair value recorded in the consolidated statement of operations and comprehensive loss as other expense, net. On May 17, 2019, immediately upon closing of the IPO, our warrants to purchase convertible preferred stock were automatically converted to warrants to purchase an equal number of shares of our Class B common stock. As a result, the warrants were remeasured a final time, immediately prior to the closing of the IPO, and reclassified to additional paid-in capital within stockholders' equity. Changes in the fair value were recorded within other expense, net on the consolidated statement of operations. As of December 31, 2019, the warrants were classified and recorded as additional paid-in capital on the condensed consolidated balance sheets. During the nine months ended September 30, 2020, the remaining Class B common stock warrants related to the previously outstanding subordinated debt and loan agreements were fully exercised under the cashless exercise method pursuant to the corresponding warrant agreements. As a result of such exercises, we issued 144,635 shares of our Class B common stock and there were no remaining outstanding common stock warrant liabilities as of September 30, 2020. No Class B common stock warrants were exercised under the cashless exercise method pursuant to the corresponding warrant agreements during the three months ended September 30, 2020.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders We compute net loss per share using the two-class method required for multiple classes of common stock and participating securities. Class A and Class B common stock are the only outstanding equity of the Company. The rights of the holders of the Class A common stock and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to 10 votes per share. Shares of Class B common stock may be converted into Class A common stock at any time at the option of the stockholder on a one-for-one basis, and are automatically converted into Class A common stock upon sale or transfer, subject to certain limited exceptions. Shares of Class A common stock are not convertible. Accordingly, the Class A common stock and Class B common stock share equally in our net losses. Prior to the IPO, our participating securities also included convertible preferred stock. The holders of convertible preferred stock did not have a contractual obligation to share in our losses, and as a result, net losses were not allocated to these participating securities. On July 12, 2021, the shares of Class B common stock that converted to Class A common stock were retired and will not be reissued by us. The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented. The shares issued in the IPO, the shares issued pursuant to the exercise by the underwriters of an option to purchase additional shares, and the shares of Class A and Class B common stock issued upon conversion of the outstanding shares of convertible preferred stock in the IPO are included in the table below, weighted for the period outstanding: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Class A (1) Class B (2) Class A (1) Class B (2) Class A (1) Class B (2) Class A (1) Class B (2) (in thousands, except per share amounts) Net loss attributable to common stockholders $ (55,109) $ (1,089) $ (20,763) $ (3,015) $ (154,623) $ (10,553) $ (39,670) $ (10,558) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 114,218 2,257 92,510 13,432 107,952 7,368 79,307 21,106 Net loss per share attributable to common stockholders, basic and diluted $ (0.48) $ (0.48) $ (0.22) $ (0.22) $ (1.43) $ (1.43) $ (0.50) $ (0.50) __________ (1) Class A common stock includes the issuance of 12.9 million shares of Class A common stock issued by us in connection with our IPO and the shares issued in connection with our follow-on offering on May 26, 2020. It also includes shares issued upon the exercise of options and vesting of RSUs granted subsequent to our IPO, shares issued as part of our prior acquisitions, and converted Common B shares. (2) Class B common stock includes, for all periods presented, common stock issued prior to the IPO and the conversion of all of our preferred stock into an aggregate of 53.6 million shares of our Class B common stock upon closing of the IPO. Some of these shares were previously converted into shares of Class A common stock. On July 12, 2021, all shares of Class B common stock were converted into shares of Class A common stock. Since we were in a loss position for the periods presented, basic net loss per share is the same as diluted net loss per share, as the inclusion of all potential common shares outstanding would have been anti-dilutive. We apply the if-converted method for calculation of diluted earnings per share for our convertible debt instruments. The potential shares of common stock that were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been antidilutive are as follows: Number of Shares As of September 30, 2021 2020 (in thousands) Stock options 5,175 7,290 RSUs 4,458 4,354 PSUs 109 88 Revest shares 448 — Early exercised stock options 48 106 Shares issuable pursuant to the ESPP 83 90 Convertible senior notes (if-converted) 9,229 — Total 19,550 11,928

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Our provision for income taxes for interim periods is determined using an estimate of our annual effective tax rate, adjusted for discrete items, if any, that arise during the period. Each quarter, we update our estimate of the annual effective tax rate, and if the estimated annual effective tax rate changes, we make a cumulative adjustment in such period. In the three months ended September 30, 2021 and 2020, we recorded income tax expense of $0.03 million and $0.3 million, respectively. In the nine months ended September 30, 2021 and 2020, we recorded income tax expenses of $0.04 million and $1.1 million, respectively. We continue to maintain a full valuation allowance on our U.S. Federal and state net deferred tax assets. The tax expense for the three and nine months ended September 30, 2021 and 2020 was primarily due to foreign and state income tax expense.

Information About Revenue and G

Information About Revenue and Geographic Areas	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Information About Revenue and Geographic Areas	Information About Revenue and Geographic Areas We consider operating segments to be components of the Company in which separate financial information is available and is evaluated regularly by our Chief Operating Decision Maker ("CODM") in deciding how to allocate resources and in assessing performance. Our CODM is the Chief Executive Officer ("CEO"). The CEO reviews financial information presented on a consolidated basis, accompanied by information about revenue, customer size, and industry vertical for purposes of allocating resources and evaluating financial performance. We have determined that we operate under one business unit with no segment managers who are held accountable for operations, operating results, or plans for levels or components below the consolidated unit level. Accordingly, we have determined that we have a single reporting segment and operating unit structure. Revenue Revenue by geography is based on the billing address of the customer. Refer to Note 3, "Revenue" for more information on net revenue by geographic region. Long-Lived Assets The following table presents long-lived assets by geographic region: As of September 30, As of December 31, 2021 2020 (in thousands) United States $ 114,130 $ 65,054 All other countries 33,599 30,925 Total long-lived assets $ 147,729 $ 95,979

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The interim unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with United States generally accepted accounting principles ("U.S. GAAP") along with instructions to Form 10-Q and Article 10 of Securities and Exchange Commission ("SEC") Regulation S-X. Certain changes in presentation have been made to conform the prior period presentation to the current period reporting. Such reclassifications did not affect total revenues, operating income, or net income. We have made certain presentation changes to distinguish and disclose as a separate line item, our Marketable securities, noncurrent balance from our Other assets line in the Condensed Consolidated Balance Sheets. We have made certain presentation changes to distinguish and disclose as separate line items, the amortization of intangible assets and depreciation expenses within operating cash flows in the Condensed Consolidated Statements of Cash Flows.
Principles of Consolidation and Unaudited Interim Financial Statements	Principles of Consolidation The accompanying interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Unaudited Interim Financial Statements The accompanying interim condensed consolidated balance sheet as of September 30, 2021, the related interim condensed consolidated statements of operations, the condensed consolidated statements of comprehensive loss, and the condensed consolidated statements of stockholders' equity for the three and nine months ended September 30, 2021 and 2020, the condensed consolidated statements of cash flows for the nine months ended September 30, 2021 and 2020, and the related footnote disclosures are unaudited. The unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. GAAP. In management’s opinion, the unaudited financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, which include only normal recurring adjustments necessary for the fair presentation of our financial position as of September 30, 2021. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results expected for the full fiscal year or any other periods.
Use of Estimates	Use of Estimates The preparation of our condensed consolidated financial statements requires us to make estimates, judgments, and assumptions that affect the reported amounts of assets, liabilities, revenue, costs and expenses and related disclosures. Actual results and outcomes could differ significantly from our estimates, judgments, and assumptions. Significant estimates, judgments, and assumptions used in these financial statements include, but are not limited to, those related to revenue, accounts receivable and related reserves, fair value of assets acquired and liabilities assumed for business combinations, useful lives and realizability of long-lived assets including our goodwill and intangible assets, income tax reserves and accounting for stock-based compensation. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. The effects of material revisions in estimates are reflected in the condensed consolidated financial statements in the period of change and prospectively from the date of the change in estimate. The ongoing global COVID-19 pandemic has adversely impacted many operational aspects of our business and may continue to do so in the future. Since the start of the pandemic, we have assessed the impact that COVID-19 had on our results of operations, including, but not limited to an assessment of our allowance for credit losses, the carrying value of short-term and long-term marketable securities, the carrying value of goodwill and other long-lived assets, and the impact on revenue recognition and cost of revenues. The future impacts of the pandemic and any resulting economic impact are largely unknown and are continuing to evolve. We will continue to actively monitor the impact that COVID-19 has on the results of our business operations, and may make decisions required by federal, state or local authorities, or that are determined to be in the best interests of our employees, customers, partners, suppliers and stockholders. As a result, our estimates and judgments may change materially as new events occur or additional information becomes available to us.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject us to significant concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, and accounts receivable. The primary focus of our investment strategy is to preserve capital and meet liquidity requirements. Our investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. To manage the risk exposure, we invest cash equivalents and marketable securities in a variety of fixed income securities, including government and investment-grade debt securities and money market funds. We place our cash primarily in checking and money market accounts with reputable financial institutions. Deposits held with these financial institutions may exceed the amount of insurance provided on such deposits, if any. Concentrations of credit risk with respect to accounts receivable are primarily limited to certain customers to which we make substantial sales. Our customer base consists of a large number of geographically dispersed customers diversified across several industries. To reduce this risk, we routinely assess the financial strength of our customers. Based on such assessments, we believe that our accounts receivable credit risk exposure is limited.
Convertible Debt	Convertible Debt We early adopted ASU 2020-06 as of January 1, 2021, which in effect, allows for the separation models for convertible debt that contain cash conversion features accounted for as a cash conversion or beneficial conversion features to be removed. We evaluated the terms of our debt in line with ASU 2020-06 and concluded that the instrument does not require separation and that there were no other derivatives that required separation. We have combined these features with the host contract and we account for our convertible debt as a single liability in long-term debt on our condensed consolidated balance sheet. The carrying amount of the liability is based on the gross proceeds, net of the unamortized transaction costs incurred related to the issuance of the convertible debt instrument. This difference represents a debt discount that is amortized to interest expense over the term of the convertible debt instrument using the effective interest rate method. We apply the if-converted method for calculation of diluted earnings per share for our convertible debt instrument.
Recently Adopted Accounting Pronouncements and Other Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements On December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740), which simplifies the accounting for income taxes, primarily by eliminating certain exceptions to ASC 740. This standard is effective for fiscal periods beginning after December 15, 2020. We adopted this standard on January 1, 2021. The adoption of this standard did not have a material impact on our consolidated financial statements. In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40). The update removes separation models for convertible debt that contain cash conversion features accounted for as a cash conversion or beneficial conversion features. Under this ASU, these features will be combined with the host contract. ASU 2020-06 does not impact the accounting treatment for conversion features that are accounted for as a derivative under Topic 815. The update also requires the application of the if-converted method to be used for convertible instruments and the effect of potential share settlement be included in the diluted earnings per share calculation when an instrument may be settled in cash or shares. The amendments in this update are effective for public business entities for fiscal years beginning after December 15, 2021, and interim periods within those fiscal years. The amendment is to be adopted through either a fully retrospective or modified retrospective method of transition, only at the beginning of an entity's fiscal year. Early adoption is permitted. We have elected to early adopt the standard as of January 1, 2021 using the modified retrospective method of transition. We evaluated the terms of our debt and concluded that the instrument does not require separation and that there were no other derivatives that required separation. As a result, there is no equity component and we recorded the convertible note as a single liability within long-term debt on our Condensed Consolidated Balance Sheet. We apply the if-converted method for calculation of diluted earnings per share for our convertible debt instruments. Other Recent Accounting Pronouncements Other recently issued accounting pronouncements are not expected to have a material impact on our condensed consolidated financial statements.
Revenue recognition	Revenue recognition Revenue is recognized upon transfer of control of promised products or services to customers in an amount that reflects the consideration we expect to receive in exchange for those products or services. The processing and recording of certain revenue requires a manual process, which uses a complex set of procedures to generate complete and accurate data to record these revenue transactions. We enter into contracts that can include various combinations of products and services, each of which are distinct and accounted for as separate performance obligations. Revenue is recognized net of any taxes collected from customers, which are subsequently remitted to governmental authorities. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account. Our contracts with customers often include promises to transfer multiple products and services to a customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment. For contracts with multiple performance obligations, we allocate the contract transaction price to each performance obligation using our estimate of the standalone selling price ("SSP") of each distinct good or service in the contract. Judgment is required to determine the SSP for each distinct performance obligation. We analyze separate sales of our products and services as a basis for estimating the SSP of our products and services. We then use the SSP as the basis for allocating the transaction price when our product and services are sold together in a contract with multiple performance obligations. In instances where SSP is not directly observable, such as when we do not sell the product or service separately, we determine the SSP using information that may include market conditions and other observable inputs. We typically have more than one SSP for individual products and services due to the stratification of those products and services by customers and circumstances. In these instances, we may use information, such as geographic region and distribution channel, in determining the SSP. The transaction price in a contract for usage-based services is typically equal to the minimum commit price in the contract less any discounts provided. The transaction price in a contract that does not contain usage-based services is equal to the total contract value. Because our typical contracts represent distinct services delivered over time with the same pattern of transfer to the customer, usage-based consideration primarily related to actual consumption over the minimum commit levels is allocated to the period to which it relates. The amount of consideration recognized for usage above the minimum commit price is limited to the amount we expect to be entitled to receive in exchange for providing services. We have elected to apply the practical expedient for estimating and disclosing the variable consideration when variable consideration is allocated entirely to a wholly unsatisfied performance obligation or to a wholly unsatisfied promise to transfer a distinct good or service that forms part of a single performance obligation from our remaining performance obligations under these contracts. Performance obligations represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by us. These obligations can be content delivery, security, subscription services, professional services, support, edge cloud platform services, and others. Accordingly, our revenue is recognized over time, consistent with the pattern of benefit provided to the customer over the term of the agreement. At times, customers may request changes that either amend, replace, or cancel existing contracts. Judgment is required to determine whether the specific facts and circumstances within the contracts should be accounted for as a separate contract or as a modification. In contracts where there are timing differences between when we transfer a promised good or service to the customer and when the customer pays for that good or service, we have determined our contracts do not include a significant financing component. We have also elected the practical expedient to not measure financing components for any contract where the timing difference is less than one year.
Fair value of financial instruments	Fair Value of Financial Instruments For certain of our financial instruments, including cash held in banks, accounts receivable, and accounts payable, the carrying amounts approximate fair value due to their short maturities, and are therefore excluded from the fair value tables below. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. There is a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1—Observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3—Unobservable inputs that are supported by little or no market activity, which require management judgment or estimation.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Schedule of Prior Period Adjustments	The following tables show the affected line items within the condensed consolidated financial statements (in millions): Condensed Consolidated Statement of Stockholders' Equity Three Months Ended September 30, 2020 As previously reported Adjustments As adjusted (in thousands) Accumulated Deficit: Balance as of June 30, 2020 $ (218,459) $ (252) $ (218,711) Balance as of September 30, 2020 $ (242,237) $ (252) $ (242,489) Total Stockholders' Equity Balance as of June 30, 2020 $ 542,165 $ (252) $ 541,913 Balance as of September 30, 2020 $ 535,120 $ (252) $ 534,868 Nine months ended September 30, 2020 As previously reported Adjustments As adjusted (in thousands) Accumulated Deficit: Balance as of December 31, 2019 $ (192,009) $ — $ (192,009) Change in accounting policy $ — $ (252) $ (252) Balance as of September 30, 2020 $ (242,237) $ (252) $ (242,489) Total Stockholders' Equity Balance as of December 31, 2019 $ 257,652 $ — $ 257,652 Change in accounting policy $ — $ (252) $ (252) Balance as of September 30, 2020 $ 535,120 $ (252) $ 534,868 Condensed Consolidated Statement of Cash Flows Nine months ended September 30, 2020 As previously reported Adjustments As adjusted (in thousands) Cash flows from operating activities: Amortization of deferred rent $ 2,941 $ (2,941) $ — Amortization of right-of-use asset and other — 15,824 15,824 Other adjustments 207 (31) 176 Operating lease liabilities — (12,852) (12,852) Net cash used in operating activities 11,233 — 11,233 Cash flows from investing activities: Purchase of property and equipment (24,443) 841 (23,602) Net cash provided by investing activities (7,588) 841 (6,747) Cash flows from financing activities: Repayments of capital lease liabilities (3,060) 3,060 — Repayments of finance lease liabilities — (3,901) (3,901) Net cash provided by financing activities $ 290,320 $ (841) $ 289,479 Supplemental disclosure of cash flow information: Capital lease outstanding on current year addition $ 5,439 $ (5,439) $ — Assets obtained in exchange for operating lease obligations $ — $ 15,095 $ 15,095 Assets obtained in exchange for finance lease obligations $ — $ 11,352 11,352

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue by Geographic Area	The following table presents our net revenue by geographic region: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) (in thousands) United States $ 62,287 $ 49,140 $ 179,860 $ 136,194 Asia Pacific 9,804 10,306 27,969 34,157 Europe 8,550 8,003 25,969 23,549 All other 6,094 3,189 22,815 14,325 Total revenue $ 86,735 $ 70,638 $ 256,613 $ 208,225
Revenue by Customer Type	The following table presents our net revenue for enterprise and non-enterprise customers: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) (in thousands) Enterprise customers $ 76,006 $ 63,353 $ 226,622 $ 186,490 Non-enterprise customers 10,729 7,285 29,991 21,735 Total revenue $ 86,735 $ 70,638 $ 256,613 $ 208,225
Contract Assets and Liabilities	The following table presents our contract assets and contract liabilities as of September 30, 2021 and as of December 31, 2020: As of September 30, 2021 As of December 31, 2020 (in thousands) Contract assets $ 181 $ 387 Contract liabilities $ 24,817 $ 18,020 The following table presents the revenue recognized during the three and nine months ended September 30, 2021 and 2020 from amounts included in the contract liability at the beginning of the period: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Revenue recognized in the period from amounts included in contract liability at the beginning of the period $ 8,815 $ 37 $ 13,942 $ 310
Costs to Obtain Contracts	As of September 30, 2021 and December 31, 2020, our costs to obtain contracts were as follows: As of September 30, 2021 As of December 31, 2020 (in thousands) Deferred contract costs, net $ 23,067 $ 19,332

Investments and Fair Value Me_2

Investments and Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Cash, Cash Equivalents, and Marketable Securities	Our total cash, cash equivalents and marketable securities consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Cash and cash equivalents: Cash $ 21,832 $ 21,273 Money market funds 259,699 36,629 Commercial paper — 4,998 Municipal securities 400 — Certificate of deposit 200 — Total cash and cash equivalents $ 282,131 $ 62,900 Marketable securities: Corporate notes and bonds $ 3,129 $ 14,314 Commercial paper 134,015 41,445 U.S. Treasury securities 190,183 75,524 Foreign government and supranational securities 10,025 — Municipal securities 2,250 — Asset-backed securities 21,688 — Total marketable securities, current $ 361,290 $ 131,283 Corporate notes and bonds 131,177 — U.S. Treasury securities 220,291 20,448 Municipal securities 2,330 — Asset-backed securities 55,332 — Foreign government and supranational securities 20,359 — Total marketable securities, non-current $ 429,489 $ 20,448 Total marketable securities $ 790,779 $ 151,731 Total cash, cash equivalents and marketable securities $ 1,072,910 $ 214,631
Schedule of Available-For-Sale Investments	The following table summarizes adjusted cost, gross unrealized gains and losses, and fair value related to available-for-sale securities classified as marketable securities on the accompanying Condensed Consolidated Balance Sheets as of September 30, 2021 and December 31, 2020: As of September 30, 2021 Amortized Gross Gross Fair (in thousands) Corporate notes and bonds $ 134,282 $ 42 $ (18) $ 134,306 Commercial paper 134,038 — (23) 134,015 U.S. Treasury securities 410,542 6 (74) 410,474 Municipal securities 4,578 2 — 4,580 Asset-backed securities 77,038 — (18) 77,020 Foreign government and supranational securities 30,394 — (10) 30,384 Total available-for-sale investments $ 790,872 $ 50 $ (143) $ 790,779 As of December 31, 2020 Amortized Gross Gross Fair (in thousands) Corporate notes and bonds $ 14,297 $ 17 $ — $ 14,314 Commercial paper 41,445 — — 41,445 U.S. Treasury securities 95,884 93 (5) 95,972 Total available-for-sale investments $ 151,626 $ 110 $ (5) $ 151,731
Financial Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis	Financial assets and liabilities measured and recorded at fair value on a recurring basis consisted of the following types of instruments: As of September 30, 2021 Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 132,880 $ — $ — $ 132,880 Certificate of deposit 200 — — 200 Municipal securities — 400 — 400 Total cash equivalents 133,080 400 — 133,480 Marketable securities: Corporate notes and bonds — 134,306 — 134,306 Commercial paper — 134,015 — 134,015 U.S. Treasury securities — 410,474 — 410,474 Municipal securities — 4,580 — 4,580 Asset-backed securities — 77,020 — 77,020 Foreign government and supranational securities — 30,384 — 30,384 Total marketable securities — 790,779 — 790,779 Restricted cash: Money market funds 893 893 Total restricted cash 893 — — 893 Total financial assets $ 134,373 $ 791,179 $ — $ 925,152 As of December 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 36,629 $ — $ — $ 36,629 Commercial paper — 4,998 — 4,998 Total cash equivalents 36,629 4,998 — 41,627 Marketable securities: Corporate notes and bonds — 14,314 — 14,314 Commercial paper — 41,445 — 41,445 U.S. Treasury securities — 95,972 — 95,972 Total marketable securities — 151,731 — 151,731 Restricted cash: Money market funds 980 — — 980 Total restricted cash 980 — — 980 Total financial assets $ 37,609 $ 156,729 $ — $ 194,338

Business Combinations (Tables)

Business Combinations (Tables)	9 Months Ended
	Sep. 30, 2021
Business Combination and Asset Acquisition [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The purchase consideration was allocated to the tangible and intangible assets and liabilities acquired as of the acquisition date, with the excess recorded to goodwill, which includes the value attributable to the assembled workforce, as shown below (in thousands): Amount Assets acquired Cash and cash equivalents $ 21,501 Other current assets 6,419 Intangible assets, net 124,100 Other non-current assets 8,094 Total assets acquired $ 160,114 Liabilities assumed Current liabilities (14,755) Non-current liabilities (21,170) Total liabilities assumed $ (35,925) Net assets acquired 124,189 Total acquisition consideration 759,393 Goodwill recorded $ 635,204
Schedule of Identifiable Finite-Lived Intangible Assets	Identifiable finite-lived intangible assets were comprised of the following: Total (in thousands) Estimated useful life (in years) Customer relationships $ 69,100 8.0 Developed technology 49,500 5.0 Trade name 3,300 3.0 Backlog 2,200 2.0 Total intangible assets acquired $ 124,100
Schedule of Pro Forma Information	The unaudited pro forma financial information was as follows (in thousands): (Unaudited) For the year ended (in thousands) Revenue $ 313,665 Net loss $ (159,248)

Balance Sheet Information (Tabl

Balance Sheet Information (Tables)	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Computer and networking equipment $ 187,050 $ 129,998 Leasehold improvements 3,793 3,817 Furniture and fixtures 1,223 1,092 Office equipment 654 659 Internal-use software 35,316 22,066 Property and equipment, gross $ 228,036 $ 157,632 Accumulated depreciation and amortization (80,307) (61,653) Property and equipment, net $ 147,729 $ 95,979
Schedule of Other Assets	Other assets consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Deferred contract costs, net $ 23,067 $ 19,332 Restricted cash 893 893 Other assets 4,182 4,692 Total other assets $ 28,142 $ 24,917
Schedule of Accrued Expenses	Accrued expenses consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Accrued compensation and related benefits $ 14,812 $ 17,840 Sales and use tax payable 7,486 6,274 Accrued acquisition-related costs — 3,644 Accrued colocation and bandwidth costs 7,231 2,208 Other accrued liabilities 6,534 4,368 Total accrued expenses $ 36,063 $ 34,334
Schedule of Other Current Liabilities	Other current liabilities consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Deferred revenue, current $ 21,631 $ 15,916 Accrued computer and networking equipment 2,274 3,126 Liability for early-exercised stock options 213 255 Other current liabilities 640 380 Total other current liabilities $ 24,758 $ 19,677
Schedule of Other Long-Term Liabilities	Other long-term liabilities consisted of the following: As of September 30, As of December 31, 2021 2020 (in thousands) Deferred revenue, non-current $ 3,186 $ 2,104 CARES Act payroll tax deferral 1,676 1,676 Other long-term liabilities 194 620 Total other long-term liabilities $ 5,056 $ 4,400

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Schedule of Lease Costs & Other Information	The components of lease cost were as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Operating lease cost: Operating lease cost $ 7,018 $ 5,578 $ 19,741 $ 15,670 Variable lease cost 1,806 1,234 4,624 2,590 Total operating lease costs $ 8,824 $ 6,812 $ 24,365 $ 18,260 Finance lease cost: Amortization of assets under finance lease $ 4,124 $ 419 $ 6,608 $ 1,827 Interest 524 186 1,259 454 Total finance lease costs $ 4,648 $ 605 $ 7,867 $ 2,281 Other information related to leases was as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Supplemental Cash Flow Information Cash paid for amounts included in the measurement of lease liabilities: Payments for operating leases liabilities included in cash from operating activities $ 6,879 $ 4,439 $ 19,735 $ 12,852 Payments for finance leases interest included in cash from operating activities $ 524 $ 186 $ 1,259 $ 454 Payments for finance leases liabilities included in cash from financing activities $ 3,985 $ 1,001 $ 10,564 $ 3,901 Assets obtained in exchange for lease obligations: Operating leases $ 12,264 $ 4,817 $ 25,745 $ 15,095 Finance leases $ 12,861 $ 3,510 $ 28,399 $ 11,352 As of September 30, As of December 31, 2021 2020 Weighted Average Remaining Lease Term (in years) Operating leases 4.44 4.44 Finance leases 2.26 2.51 Weighted Average Discount Rate Operating leases 5.29 % 5.68 % Finance leases 4.92 % 5.12 %
Schedule of Operating Lease Maturities	Future minimum lease payments under non-cancellable leases as of September 30, 2021 were as follows: Operating Leases Finance Leases (in thousands) Remainder of 2021 $ 7,108 $ 5,268 2022 24,241 19,414 2023 17,710 15,930 2024 13,337 4,788 2025 12,395 — Thereafter 17,208 — Total future minimum lease payments $ 91,999 $ 45,400 Less: imputed interest (9,943) (2,062) Total liability $ 82,056 $ 43,338
Schedule of Finance Lease Maturity	Future minimum lease payments under non-cancellable leases as of September 30, 2021 were as follows: Operating Leases Finance Leases (in thousands) Remainder of 2021 $ 7,108 $ 5,268 2022 24,241 19,414 2023 17,710 15,930 2024 13,337 4,788 2025 12,395 — Thereafter 17,208 — Total future minimum lease payments $ 91,999 $ 45,400 Less: imputed interest (9,943) (2,062) Total liability $ 82,056 $ 43,338

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the nine months ended September 30, 2021 are as follows: Nine months ended September 30, 2021 (in thousands) Balance as of December 31, 2020 $ 635,590 Foreign currency translation and other adjustments 45 Balance as of September 30, 2021 $ 635,635
Schedule of Intangible Assets	As of September 30, 2021 and December 31, 2020, our intangible assets consisted of the following: As of September 30, 2021 As of December 31, 2020 Gross carrying value Accumulated amortization Net carrying value Gross carrying value Accumulated amortization Net carrying value (in thousands) Intangible assets: Customer relationships $ 69,100 $ (8,638) $ 60,462 $ 69,100 $ (2,053) $ 67,047 Developed technology 49,500 (9,900) 39,600 49,500 (2,475) 47,025 Trade names 3,300 (1,100) 2,200 3,300 (275) 3,025 Internet protocol addresses 4,984 (848) 4,136 2,891 (578) 2,313 Backlog 2,200 (1,100) 1,100 2,200 (275) 1,925 In-process research and development ("IPR&D") 368 — 368 368 — 368 Domain name 39 — 39 39 — 39 Total intangible assets $ 129,491 $ (21,586) $ 107,905 $ 127,398 $ (5,656) $ 121,742
Expected Amortization Expense of Intangible Assets	The annual expected amortization expense of intangible assets subject to amortization as of September 30, 2021 is as follows: As of September 30, 2021 (in thousands) Remainder of 2021 $ 5,313 2022 20,974 2023 19,874 2024 19,040 2025 16,561 Thereafter 25,771 Total $ 107,533

Debt Instruments (Tables)

Debt Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Carrying Values of Debt Agreements	The following table reflects the carrying values of the debt agreements as of September 30, 2021: As of September 30, 2021 (in thousands) Convertible Senior notes (effective interest rate of 0.40%) Principal amount $ 948,750 Less: unamortized debt issuance costs (16,445) Less: current portion of long-term debt — Long-term debt, less current portion $ 932,305

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Purchase Commitments	Our minimum future commitments related to our purchase commitments as of September 30, 2021 were as follows: Cost of Revenue Commitments SaaS Agreements Total Purchase Commitments (in thousands) Remainder of 2021 $ 13,468 $ 4,381 $ 17,849 2022 27,771 14,590 42,361 2023 5,502 12,814 18,316 2024 2,920 140 3,060 2025 160 — 160 Thereafter 46 — 46 Total $ 49,867 $ 31,925 $ 81,792

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Schedule of Stock Option Activity	The following table summarizes stock option activity during the nine months ended September 30, 2021: Shares Weighted- Weighted- Aggregate (in thousands) (in years) (in thousands) Outstanding at December 31, 2020 6,963 $ 5.63 6.7 $ 569,094 Granted — — Exercised (1,527) 5.96 Cancelled/forfeited (261) 11.00 Outstanding at September 30, 2021 5,175 $ 5.27 5.2 $ 182,027 Vested and exercisable at September 30, 2021 3,912 $ 3.97 4.6 $ 142,675 Unvested and exercisable at September 30, 2021 173 $ 6.65 7.1 $ 5,841
Schedule of Unvested Exercised Options	The activity of non-vested shares as a result of early exercise of options granted to employees and non-employees, is as follows: Nine months ended September 30, 2021 (in thousands) Beginning balance as of December 31, 2020 91 Early exercise of options — Vested (43) Repurchased — Ending balance as of September 30, 2021 48
Schedule of Restricted Stock Units	The following table summarizes RSU activity during the nine months ended September 30, 2021: Number of Shares Weighted-Average (in thousands) Unvested RSUs as of December 31, 2020 4,520 $ 30.01 Granted 1,890 63.95 Vested (1,463) 33.52 Cancelled/forfeited (470) 42.78 Unvested RSUs as of September 30, 2021 4,477 $ 41.85 The following table summarizes the activity related to the revest shares during the nine months ended September 30, 2021: Number of Shares Weighted-Average (in thousands) Unvested revest shares as of December 31, 2020 784 $ 97.84 Vested (336) 97.84 Cancelled/forfeited — Unvested revest shares as of September 30, 2021 448 $ 97.84 The following table summarizes the activity related to the PSUs during the nine months ended September 30, 2021: Number of Shares Weighted-Average (in thousands) Unvested PSUs as of December 31, 2020 88 $ 65.11 Granted 71 102.06 Vested (57) 44.25 Cancelled/forfeited (12) 44.25 Unvested PSUs as of September 30, 2021 90 $ 110.29
Employee Stock Purchase Plan, Valuation Assumptions	We estimated the fair value of shares granted under the ESPP using the Black-Scholes option pricing model with the following assumptions: Nine months ended September 30, 2021 2020 Fair value of common stock $12.66 - $24.07 $6.02 - 14.09 Expected term (in years) 0.49 to 0.50 0.50 Risk-free interest rate 0.02% - 0.10% 0.14% - 1.59% Expected volatility 47% - 50% 43% - 60% Dividend yield —% —%
Schedule of Stock-Based Compensation Expense	The following table summarizes the components of total stock-based compensation expense included in the accompanying Condensed Consolidated Statements of Operations: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 (in thousands) Stock-based compensation expense by caption: Cost of revenue $ 1,897 $ 929 $ 4,911 $ 2,634 Research and development 14,752 4,371 31,344 10,095 Sales and marketing 9,121 3,194 19,760 11,753 General and administrative 10,866 3,648 44,885 10,270 Total $ 36,636 $ 12,142 $ 100,900 $ 34,752

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The shares issued in the IPO, the shares issued pursuant to the exercise by the underwriters of an option to purchase additional shares, and the shares of Class A and Class B common stock issued upon conversion of the outstanding shares of convertible preferred stock in the IPO are included in the table below, weighted for the period outstanding: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Class A (1) Class B (2) Class A (1) Class B (2) Class A (1) Class B (2) Class A (1) Class B (2) (in thousands, except per share amounts) Net loss attributable to common stockholders $ (55,109) $ (1,089) $ (20,763) $ (3,015) $ (154,623) $ (10,553) $ (39,670) $ (10,558) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 114,218 2,257 92,510 13,432 107,952 7,368 79,307 21,106 Net loss per share attributable to common stockholders, basic and diluted $ (0.48) $ (0.48) $ (0.22) $ (0.22) $ (1.43) $ (1.43) $ (0.50) $ (0.50) __________ (1) Class A common stock includes the issuance of 12.9 million shares of Class A common stock issued by us in connection with our IPO and the shares issued in connection with our follow-on offering on May 26, 2020. It also includes shares issued upon the exercise of options and vesting of RSUs granted subsequent to our IPO, shares issued as part of our prior acquisitions, and converted Common B shares.
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The potential shares of common stock that were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been antidilutive are as follows: Number of Shares As of September 30, 2021 2020 (in thousands) Stock options 5,175 7,290 RSUs 4,458 4,354 PSUs 109 88 Revest shares 448 — Early exercised stock options 48 106 Shares issuable pursuant to the ESPP 83 90 Convertible senior notes (if-converted) 9,229 — Total 19,550 11,928

Information About Revenue and_2

Information About Revenue and Geographic Areas (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Schedule of Long-Lived Assets by Geographic Region	The following table presents long-lived assets by geographic region: As of September 30, As of December 31, 2021 2020 (in thousands) United States $ 114,130 $ 65,054 All other countries 33,599 30,925 Total long-lived assets $ 147,729 $ 95,979

Nature of Business (Details)

Nature of Business (Details)	9 Months Ended
	Sep. 30, 2021operatingMarket
Class of Stock [Line Items]
Number of operating markets	68
Common Class B
Class of Stock [Line Items]
Automatic conversion provision, percentage of Class A Common Stock	10.00%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Revision of Prior Period (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Stockholders' Equity
Total stockholders’ equity (deficit)	$ 1,015,579	$ 534,868	$ 1,015,579	$ 534,868	$ 1,029,090	$ 1,061,865	$ 541,913	$ 257,652
Cash flows from operating activities:
Amortization of deferred rent				0
Amortization of right-of-use asset and other			19,818	15,824
Other adjustments			1,496	176
Operating lease liabilities			(19,735)	(12,852)
Net cash used in operating activities			(30,574)	11,233
Cash flows from investing activities:
Purchase of property and equipment			(31,267)	(23,602)
Net cash provided by investing activities			(683,847)	(6,747)
Cash flows from financing activities:
Repayments of capital lease liabilities				0
Repayments of finance lease liabilities	(3,985)	(1,001)	(10,564)	(3,901)
Net cash provided by financing activities			933,948	289,479
Supplemental disclosure of cash flow information:
Capital lease outstanding on current year addition				0
Assets obtained in exchange for operating lease obligations	12,264	4,817	25,745	15,095
Assets obtained in exchange for finance lease obligations	12,861	3,510	28,399	11,352
Cumulative Effect, Period of Adoption, Adjustment
Stockholders' Equity
Total stockholders’ equity (deficit)								(252)
As previously reported
Stockholders' Equity
Total stockholders’ equity (deficit)		535,120		535,120			542,165	257,652
Cash flows from operating activities:
Amortization of deferred rent				2,941
Amortization of right-of-use asset and other				0
Other adjustments				207
Operating lease liabilities				0
Net cash used in operating activities				11,233
Cash flows from investing activities:
Purchase of property and equipment				(24,443)
Net cash provided by investing activities				(7,588)
Cash flows from financing activities:
Repayments of capital lease liabilities				(3,060)
Repayments of finance lease liabilities				0
Net cash provided by financing activities				290,320
Supplemental disclosure of cash flow information:
Capital lease outstanding on current year addition				5,439
Assets obtained in exchange for operating lease obligations				0
Assets obtained in exchange for finance lease obligations				0
As previously reported | Cumulative Effect, Period of Adoption, Adjustment
Stockholders' Equity
Total stockholders’ equity (deficit)								0
Adjustments
Stockholders' Equity
Total stockholders’ equity (deficit)		(252)		(252)			(252)	0
Cash flows from operating activities:
Amortization of deferred rent				(2,941)
Amortization of right-of-use asset and other				15,824
Other adjustments				(31)
Operating lease liabilities				(12,852)
Net cash used in operating activities				0
Cash flows from investing activities:
Purchase of property and equipment				841
Net cash provided by investing activities				841
Cash flows from financing activities:
Repayments of capital lease liabilities				3,060
Repayments of finance lease liabilities				(3,901)
Net cash provided by financing activities				(841)
Supplemental disclosure of cash flow information:
Capital lease outstanding on current year addition				(5,439)
Assets obtained in exchange for operating lease obligations				15,095
Assets obtained in exchange for finance lease obligations				11,352
Adjustments | Cumulative Effect, Period of Adoption, Adjustment
Stockholders' Equity
Total stockholders’ equity (deficit)								(252)
Accumulated Deficit
Stockholders' Equity
Total stockholders’ equity (deficit)	$ (453,369)	(242,489)	$ (453,369)	(242,489)	$ (397,171)	$ (288,193)	(218,711)	(192,009)
Accumulated Deficit | Cumulative Effect, Period of Adoption, Adjustment
Stockholders' Equity
Total stockholders’ equity (deficit)								(252)
Accumulated Deficit | As previously reported
Stockholders' Equity
Total stockholders’ equity (deficit)		(242,237)		(242,237)			(218,459)	(192,009)
Accumulated Deficit | As previously reported | Cumulative Effect, Period of Adoption, Adjustment
Stockholders' Equity
Total stockholders’ equity (deficit)								0
Accumulated Deficit | Adjustments
Stockholders' Equity
Total stockholders’ equity (deficit)		$ (252)		$ (252)			$ (252)	0
Accumulated Deficit | Adjustments | Cumulative Effect, Period of Adoption, Adjustment
Stockholders' Equity
Total stockholders’ equity (deficit)								$ (252)

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Concentrations of Credit Risk (Details) - Major Customer - Customer Concentration Risk	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020
Revenue
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%
Accounts Receivable
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	10.00%

Revenue - Narrative (Details)

Revenue - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Concentration Risk [Line Items]
Enterprise customer threshold	$ 100,000		$ 100,000
Revenue, performance obligation, description of payment terms			Payment terms on invoiced amounts are at an average of 40 days.
Capitalized contract costs, amortization period	5 years		5 years
Amortization of deferred contract costs	$ 1,600,000	$ 900,000	$ 4,567,000	$ 2,375,000
Singapore | Revenue | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage				11.00%

Revenue - Revenue by Geographic

Revenue - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 86,735	$ 70,638	$ 256,613	$ 208,225
United States
Disaggregation of Revenue [Line Items]
Total revenue	62,287	49,140	179,860	136,194
Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenue	9,804	10,306	27,969	34,157
Europe
Disaggregation of Revenue [Line Items]
Total revenue	8,550	8,003	25,969	23,549
All other
Disaggregation of Revenue [Line Items]
Total revenue	$ 6,094	$ 3,189	$ 22,815	$ 14,325

Revenue - Revenue by Customer T

Revenue - Revenue by Customer Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 86,735	$ 70,638	$ 256,613	$ 208,225
Enterprise customers
Disaggregation of Revenue [Line Items]
Total revenue	76,006	63,353	226,622	186,490
Non-enterprise customers
Disaggregation of Revenue [Line Items]
Total revenue	$ 10,729	$ 7,285	$ 29,991	$ 21,735

Revenue - Contract Assets and L

Revenue - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract assets	$ 181		$ 181		$ 387
Contract liabilities	24,817		24,817		$ 18,020
Contract with Customer, Liability
Revenue recognized in the period from amounts included in contract liability at the beginning of the period	$ 8,815	$ 37	$ 13,942	$ 310

Revenue - Remaining Performance

Revenue - Remaining Performance Obligation (Details) $ in Millions	Sep. 30, 2021USD ($)
Revenue from Contract with Customer [Abstract]
Revenue performance obligation	$ 147.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, percentage	84.00%
Remaining performance obligation, timing of satisfaction	12 months

Revenue - Costs to Obtain Contr

Revenue - Costs to Obtain Contracts (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Deferred contract costs, net	$ 23,067	$ 19,332

Investments and Fair Value Me_3

Investments and Fair Value Measurements - Cash, Cash Equivalent and Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents:	$ 282,131	$ 62,900	$ 309,968
Marketable securities, current	361,290	131,283
Marketable securities, noncurrent	429,489	20,448
Total marketable securities	790,779	151,731
Total cash, cash equivalents and marketable securities	1,072,910	214,631
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	3,129	14,314
Marketable securities, noncurrent	131,177	0
Total marketable securities	134,306	14,314
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	134,015	41,445
Total marketable securities	134,015	41,445
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	190,183	75,524
Marketable securities, noncurrent	220,291	20,448
Total marketable securities	410,474	95,972
Foreign government and supranational securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	10,025	0
Marketable securities, noncurrent	20,359	0
Total marketable securities	30,384
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	2,250	0
Total marketable securities	4,580
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, noncurrent	2,330	0
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities, current	21,688	0
Marketable securities, noncurrent	55,332	0
Total marketable securities	77,020
Cash
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents:	21,832	21,273
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents:	259,699	36,629
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents:	0	4,998
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents:	400	0
Certificate of deposit
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents:	$ 200	$ 0

Investments and Fair Value Me_4

Investments and Fair Value Measurements - Available-For-Sale Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 790,872	$ 151,626
Gross Unrealized Gain	50	110
Gross Unrealized Loss	(143)	(5)
Fair Value	790,779	151,731
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	134,282	14,297
Gross Unrealized Gain	42	17
Gross Unrealized Loss	(18)	0
Fair Value	134,306	14,314
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	134,038	41,445
Gross Unrealized Gain	0	0
Gross Unrealized Loss	(23)	0
Fair Value	134,015	41,445
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	410,542	95,884
Gross Unrealized Gain	6	93
Gross Unrealized Loss	(74)	(5)
Fair Value	410,474	$ 95,972
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,578
Gross Unrealized Gain	2
Gross Unrealized Loss	0
Fair Value	4,580
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	77,038
Gross Unrealized Gain	0
Gross Unrealized Loss	(18)
Fair Value	77,020
Foreign government and supranational securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	30,394
Gross Unrealized Gain	0
Gross Unrealized Loss	(10)
Fair Value	$ 30,384

Investments and Fair Value Me_5

Investments and Fair Value Measurements - Narrative (Details) - security	Sep. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Securities in a continuous loss position (in securities)	0	0

Investments and Fair Value Me_6

Investments and Fair Value Measurements - Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 133,480	$ 41,627
Marketable securities	790,779	151,731
Restricted cash	893	980
Total financial assets	925,152	194,338
Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	134,306	14,314
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	134,015	41,445
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	410,474	95,972
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	4,580
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	77,020
Foreign government and supranational securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	30,384
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	132,880	36,629
Restricted cash	893	980
Certificate of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	200
Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	400
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		4,998
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	133,080	36,629
Marketable securities	0	0
Restricted cash	893	980
Total financial assets	134,373	37,609
Level 1 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Level 1 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Level 1 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Level 1 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Level 1 | Foreign government and supranational securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	132,880	36,629
Restricted cash	893	980
Level 1 | Certificate of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	200
Level 1 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	400	4,998
Marketable securities	790,779	151,731
Restricted cash	0	0
Total financial assets	791,179	156,729
Level 2 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	134,306	14,314
Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	134,015	41,445
Level 2 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	410,474	95,972
Level 2 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	4,580
Level 2 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	77,020
Level 2 | Foreign government and supranational securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	30,384
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Restricted cash		0
Level 2 | Certificate of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Level 2 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	400
Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		4,998
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Marketable securities	0	0
Restricted cash	0	0
Total financial assets	0	0
Level 3 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Level 3 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Level 3 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Level 3 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Level 3 | Foreign government and supranational securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Restricted cash		0
Level 3 | Certificate of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Level 3 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 0
Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		$ 0

Business Combinations - Narrati

Business Combinations - Narrative (Details) $ / shares in Units, $ in Thousands	Oct. 01, 2020USD ($)cofounder$ / sharesshares	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	May 31, 2019$ / shares
Business Acquisition [Line Items]
Revenue		$ 86,735		$ 70,638	$ 256,613	$ 208,225
Net loss		$ 56,198		$ 23,778	$ 165,176	$ 50,228
Common Class A
Business Acquisition [Line Items]
Common stock, par value (in USD per share) | $ / shares								$ 0.00002
Signal Sciences Corp.
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired	100.00%
Aggregate consideration transferred	$ 759,400
Cash consideration transferred	223,000
Acquisition, value of equity consideration	$ 536,400
Number of cofounders with shares subject to revesting | cofounder	3
Shares held back for restricted stock awards, revesting period	2 years
Unvested stock option assumed, fair value	$ 21,800
Amount allocated to purchase price	1,100
Amount allocated to future services	$ 20,700
Amount allocated to future services, recognition period	2 years 6 months
Unvested stock options assumed, conversion ratio	10.00%
Estimated useful life (in years)	6 years 7 months 6 days
Tax benefit from release of valuation allowance							$ 13,000
Acquisition related costs							$ 20,800
Revenue			$ 6,700
Net loss			$ 23,000
Signal Sciences Corp. | Common Class A
Business Acquisition [Line Items]
Shares issued related to a business combination (in shares) | shares	6,367,709
Number of shares issued in acquisition (in shares) | shares	5,471,210
Number of shares restricted for stock awards (in shares) | shares	896,499
Common stock, par value (in USD per share) | $ / shares	$ 0.00002
Unvested stock options assumed (in shares) | shares	251,754

Business Combinations - Assets

Business Combinations - Assets Acquired and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Oct. 01, 2020
Business Acquisition [Line Items]
Goodwill recorded	$ 635,635	$ 635,590
Signal Sciences Corp.
Business Acquisition [Line Items]
Cash and cash equivalents			$ 21,501
Other current assets			6,419
Intangible assets, net			124,100
Other non-current assets			8,094
Total assets acquired			160,114
Current liabilities			(14,755)
Non-current liabilities			(21,170)
Total liabilities assumed			(35,925)
Net assets acquired			124,189
Total acquisition consideration			759,393
Goodwill recorded			$ 635,204

Business Combinations - Finite-

Business Combinations - Finite-Lived Intangible Assets (Details) - Signal Sciences Corp. $ in Thousands	Oct. 01, 2020USD ($)
Business Acquisition [Line Items]
Total intangible assets acquired	$ 124,100
Estimated useful life (in years)	6 years 7 months 6 days
Customer relationships
Business Acquisition [Line Items]
Total intangible assets acquired	$ 69,100
Estimated useful life (in years)	8 years
Developed technology
Business Acquisition [Line Items]
Total intangible assets acquired	$ 49,500
Estimated useful life (in years)	5 years
Trade name
Business Acquisition [Line Items]
Total intangible assets acquired	$ 3,300
Estimated useful life (in years)	3 years
Backlog
Business Acquisition [Line Items]
Total intangible assets acquired	$ 2,200
Estimated useful life (in years)	2 years

Business Combinations - Pro For

Business Combinations - Pro Forma Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Business Combination and Asset Acquisition [Abstract]
Revenue	$ 313,665
Net loss	$ (159,248)

Balance Sheet Information - Pro

Balance Sheet Information - Property and equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 228,036	$ 157,632
Accumulated depreciation and amortization	(80,307)	(61,653)
Property and equipment, net	147,729	95,979
Computer and networking equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	187,050	129,998
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,793	3,817
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,223	1,092
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	654	659
Internal-use software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	35,316	22,066
Property and equipment, net	$ 24,400	$ 14,200

Balance Sheet Information - Nar

Balance Sheet Information - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 7,400			$ 4,900	$ 20,700	$ 14,300
Additions to capitalized internal-use software	5,100
Previously expensed capitalized internal-use software		$ 2,700	$ 2,400
Property and equipment, net	147,729				147,729		$ 95,979
Finance lease, right-of-use asset, before accumulated amortization	56,800				56,800		36,200
Finance lease, right-of-use asset, accumulated amortization	13,000				13,000		6,700
Research and development
Property, Plant and Equipment [Line Items]
Previously expensed capitalized internal-use software		2,300	2,000
Cost of revenue
Property, Plant and Equipment [Line Items]
Previously expensed capitalized internal-use software		$ 400	$ 400
Internal-use software
Property, Plant and Equipment [Line Items]
Depreciation and amortization	1,300			$ 500	3,200	$ 1,700
Property and equipment, net	$ 24,400				$ 24,400		$ 14,200

Balance Sheet Information - Oth

Balance Sheet Information - Other Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Deferred contract costs, net	$ 23,067	$ 19,332
Restricted cash	893	893
Other assets	4,182	4,692
Total other assets	$ 28,142	$ 24,917

Balance Sheet Information - Acc

Balance Sheet Information - Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued compensation and related benefits	$ 14,812	$ 17,840
Sales and use tax payable	7,486	6,274
Accrued acquisition-related costs	0	3,644
Accrued colocation and bandwidth costs	7,231	2,208
Other accrued liabilities	6,534	4,368
Total accrued expenses	$ 36,063	$ 34,334

Balance Sheet Information - O_2

Balance Sheet Information - Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Deferred revenue, current	$ 21,631	$ 15,916
Accrued computer and networking equipment	2,274	3,126
Liability for early-exercised stock options	213	255
Other current liabilities	640	380
Total other current liabilities	$ 24,758	$ 19,677

Balance Sheet Information - O_3

Balance Sheet Information - Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Deferred revenue, non-current	$ 3,186	$ 2,104
CARES Act payroll tax deferral	1,676	1,676
Other long-term liabilities	194	620
Total other long-term liabilities	$ 5,056	$ 4,400

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lessee, Lease, Description [Line Items]
Subleases, remaining lease terms (in years)			3 years
Sublease income	$ 0.2	$ 0.3	$ 0.7	$ 0.9
Lease not yet commenced, commitment amount	$ 7		$ 7
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease terms, operating (in years)	1 month 6 days		1 month 6 days
Remaining lease terms, finance (in years)	1 month 6 days		1 month 6 days
Lease not yet commenced, term of contract	1 year		1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease terms, operating (in years)	6 years		6 years
Remaining lease terms, finance (in years)	6 years		6 years
Lease not yet commenced, term of contract	6 years		6 years

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease cost	$ 7,018	$ 5,578	$ 19,741	$ 15,670
Variable lease cost	1,806	1,234	4,624	2,590
Total operating lease costs	8,824	6,812	24,365	18,260
Amortization of assets under finance lease	4,124	419	6,608	1,827
Interest	524	186	1,259	454
Total finance lease costs	$ 4,648	$ 605	$ 7,867	$ 2,281

Leases - Supplemental Lease Inf

Leases - Supplemental Lease Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Payments for operating leases liabilities included in cash from operating activities	$ 6,879	$ 4,439	$ 19,735	$ 12,852
Payments for finance leases interest included in cash from operating activities	524	186	1,259	454
Payments for finance leases liabilities included in cash from financing activities	3,985	1,001	10,564	3,901
Assets obtained in exchange for lease obligations:
Operating leases	12,264	4,817	25,745	15,095
Finance leases	$ 12,861	$ 3,510	$ 28,399	$ 11,352
Weighted Average Remaining Lease Term (in years)
Operating leases	4 years 5 months 8 days		4 years 5 months 8 days		4 years 5 months 8 days
Finance leases	2 years 3 months 3 days		2 years 3 months 3 days		2 years 6 months 3 days
Weighted Average Discount Rate
Operating leases	5.29%		5.29%		5.68%
Finance leases	4.92%		4.92%		5.12%

Leases - Lease Liability Maturi

Leases - Lease Liability Maturity (Details) $ in Thousands	Sep. 30, 2021USD ($)
Operating Leases
Remainder of 2021	$ 7,108
2022	24,241
2023	17,710
2024	13,337
2025	12,395
Thereafter	17,208
Total future minimum lease payments	91,999
Less: imputed interest	(9,943)
Total liability	82,056
Finance Leases
Remainder of 2021	5,268
2022	19,414
2023	15,930
2024	4,788
2025	0
Thereafter	0
Total future minimum lease payments	45,400
Less: imputed interest	(2,062)
Total liability	$ 43,338

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2020	$ 635,590
Foreign currency translation and other adjustments	45
Balance as of September 30, 2021	$ 635,635

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ (21,586)	$ (5,656)
Total	107,533
Gross carrying value	129,491	127,398
Total intangible assets	107,905	121,742
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	69,100	69,100
Accumulated amortization	(8,638)	(2,053)
Total	60,462	67,047
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	49,500	49,500
Accumulated amortization	(9,900)	(2,475)
Total	39,600	47,025
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	3,300	3,300
Accumulated amortization	(1,100)	(275)
Total	2,200	3,025
Internet protocol addresses
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	4,984	2,891
Accumulated amortization	(848)	(578)
Total	4,136	2,313
Backlog
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	2,200	2,200
Accumulated amortization	(1,100)	(275)
Total	1,100	1,925
In-process research and development ("IPR&D")
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	368	368
Accumulated amortization	0	0
Total	368	368
Domain name
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	39	39
Accumulated amortization	0	0
Total	$ 39	$ 39

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Purchases of intangible assets			$ 2,092	$ 1,811
Amortization of intangible assets	$ 5,300	$ 100	$ 15,929	$ 145

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Expected Amortization of Intangible Assets (Details) $ in Thousands	Sep. 30, 2021USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2021	$ 5,313
2022	20,974
2023	19,874
2024	19,040
2025	16,561
Thereafter	25,771
Total	$ 107,533

Debt Instruments - Cash Collate

Debt Instruments - Cash Collateralized Revolving Credit Agreement (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Nov. 30, 2020	Nov. 30, 2019
Debt Instrument [Line Items]
Amount of debt outstanding		$ 20,300,000
Cash collateral for line of credit		$ 70,100,000
Line of Credit | Second Lien Credit Facility
Debt Instrument [Line Items]
Debt facility, maximum borrowing amount			$ 70,000,000
Effective interest rate	3.46%
Line of credit, unused capacity, commitment fee percentage	0.20%
Line of Credit | Second Lien Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%

Debt Instruments - Senior Secur

Debt Instruments - Senior Secured Credit Facilities Agreement (Details)	Feb. 16, 2021USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2021USD ($)	Nov. 30, 2020USD ($)
Debt Instrument [Line Items]
Amount of debt outstanding				$ 20,300,000
SVB Revolver
Debt Instrument [Line Items]
Debt facility, maximum borrowing amount	$ 100,000,000
Debt covenant, adjusted quick ratio, minimum requirement	1.25
Debt covenant, adjusted quick ratio, minimum threshold to trigger revenue growth covenant requirement	1.75
Transaction costs	$ 600,000
Amounts drawn on line of credit during the period		$ 0	$ 0
Amount of debt outstanding		$ 0	$ 0
SVB Revolver | Minimum
Debt Instrument [Line Items]
Line of credit, unused capacity, commitment fee percentage	0.20%
SVB Revolver | Maximum
Debt Instrument [Line Items]
Line of credit, unused capacity, commitment fee percentage	0.25%
SVB Revolver | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
SVB Revolver | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.00%

Debt Instruments - Convertible

Debt Instruments - Convertible Senior Notes (Details) $ / shares in Units, $ in Thousands	Mar. 05, 2021USD ($)	Sep. 30, 2021USD ($)day$ / shares	Sep. 30, 2020USD ($)
Debt Instrument [Line Items]
Issuance of convertible note, net of issuance costs | $		$ 930,775	$ 0
2026 Convertible Notes
Debt Instrument [Line Items]
Issuance of convertible note, net of issuance costs | $	$ 930,000
2026 Convertible Notes | Common Class A
Debt Instrument [Line Items]
Debt instrument, convertible, conversion ratio		0.0097272
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares		$ 102.80
2026 Convertible Notes | Fastly Conversion Option
Debt Instrument [Line Items]
Debt instrument, convertible, threshold percentage of stock price trigger		130.00%
Debt instrument, convertible, threshold trading days		20
Debt instrument, convertible, threshold consecutive trading days		30
2026 Convertible Notes | Holder Conversion Option One | Common Class A
Debt Instrument [Line Items]
Debt instrument, convertible, threshold percentage of stock price trigger		130.00%
Debt instrument, convertible, threshold trading days		20
Debt instrument, convertible, threshold consecutive trading days		30
2026 Convertible Notes | Holder Conversion Option Two | Common Class A
Debt Instrument [Line Items]
Debt instrument, convertible, threshold percentage of stock price trigger		98.00%
Debt instrument, convertible, threshold trading days		5
Debt instrument, convertible, threshold consecutive trading days		10
Convertible Debt | 2026 Convertible Notes
Debt Instrument [Line Items]
Debt Instrument, face amount | $	$ 948,800
Interest rate, stated percentage	0.00%
Debt instrument, face amount, additional principal issuable | $	$ 123,800
Discount and transaction costs | $	$ 18,600
Convertible Debt | 2026 Convertible Notes | Fastly Conversion Option
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage		100.00%
Convertible Debt | 2026 Convertible Notes | Fundamental Change
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage		100.00%

Debt Instruments - Schedule of

Debt Instruments - Schedule of Outstanding Debt (Details) - Convertible Debt - 2026 Convertible Notes $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Debt Instrument [Line Items]
Effective interest rate	0.40%
Principal amount	$ 948,750
Less: unamortized debt issuance costs	(16,445)
Less: current portion of long-term debt	0
Long-term debt, less current portion	$ 932,305

Debt Instruments - Narrative (D

Debt Instruments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Interest expense	$ 1	$ 0.4	$ 2.4	$ 1.1
Finance Lease Obligations and Other Costs
Debt Instrument [Line Items]
Interest expense		$ 0.3		$ 0.5

Commitments and Contingencies -

Commitments and Contingencies - Purchase Commitments (Details) $ in Thousands	Sep. 30, 2021USD ($)
Long-term Purchase Commitment [Line Items]
Remainder of 2021	$ 17,849
2022	42,361
2023	18,316
2024	3,060
2025	160
Thereafter	46
Total	81,792
Cost of Revenue Commitments
Long-term Purchase Commitment [Line Items]
Remainder of 2021	13,468
2022	27,771
2023	5,502
2024	2,920
2025	160
Thereafter	46
Total	49,867
SaaS Agreements
Long-term Purchase Commitment [Line Items]
Remainder of 2021	4,381
2022	14,590
2023	12,814
2024	140
2025	0
Thereafter	0
Total	$ 31,925

Commitments and Contingencies_2

Commitments and Contingencies - Narrative (Details) $ in Millions	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Sep. 27, 2020lawsuit
Commitments and Contingencies Disclosure [Abstract]
Sales and use tax liability | $	$ 7.5	$ 6.3
Number of lawsuits consolidated			2
Number of lawsuits			1

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock and Preferred Stock (Details)	Jul. 12, 2021shares	Sep. 30, 2021voteshares	Dec. 31, 2020shares	May 31, 2019vote$ / sharesshares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)				10,000,000
Preferred stock, par value (in USD per share) | $ / shares				$ 0.00002
Preferred stock, shares outstanding (in shares)		0	0
Preferred stock, shares issued (in shares)		0	0
Common Class A
Class of Stock [Line Items]
Common stock, shares authorized (in shares)				1,000,000,000
Common stock, par value (in USD per share) | $ / shares				$ 0.00002
Common stock, voting rights (votes per share) | vote		1		1
Common stock, shares issued (in shares)		117,200,000	103,400,000
Common stock, shares outstanding (in shares)		117,200,000	103,400,000
Common Class B
Class of Stock [Line Items]
Common stock, shares authorized (in shares)				94,100,000
Common stock, voting rights (votes per share) | vote		10		10
Common stock, shares issued (in shares)		0	10,200,000
Common stock, shares outstanding (in shares)		0	10,200,000
Automatic conversion provision, percentage of Class A Common Stock		10.00%
Shares retired (in shares)	90,000,000

Stockholders' Equity - Equity I

Stockholders' Equity - Equity Incentive Plans (Details) - USD ($)	Oct. 01, 2020	May 31, 2019	Sep. 30, 2021	Dec. 31, 2020
Common Class A | Signal Sciences Corp.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested stock options assumed (in shares)	251,754
Shares issuable pursuant to the ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum deduction of eligible compensation		15.00%
Maximum purchase value during offering period, per employee		$ 25,000
Shares issuable pursuant to the ESPP | Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares reserved for future issuance (in shares)			4,600,000	3,500,000
Common stock, shares available for future issuance (in shares)			3,800,000	2,800,000
2011 Equity Incentive Plan | Common Class B
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares reserved for future issuance (in shares)				23,600,000
Common stock, shares available for future issuance (in shares)				0
2011 Equity Incentive Plan | Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares reserved for future issuance (in shares)			23,600,000
Common stock, shares available for future issuance (in shares)			0
2019 Equity Incentive Plan | Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares reserved for future issuance (in shares)			25,100,000	19,400,000
Common stock, shares available for future issuance (in shares)			17,100,000	12,800,000

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Options (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pre-tax intrinsic value			$ 52,600	$ 157,900
Vesting of early exercised stock options			$ 8,300	$ 6,500
Granted (in shares)	0	0	0	0
Stock-based compensation expense	$ 36,636	$ 12,142	$ 100,900	$ 34,752
Modification expense	2,400	400	3,700	400
Modification expense, incremental fair value	2,100	300	3,300	300
Unrecognized stock-based compensation cost	14,500		14,500
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5,300	1,800	$ 13,400	5,700
Weighted-average period of recognition			1 year 2 months 23 days
Stock options | 2011 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period			10 years
Award vesting period			4 years
Stock options | 2011 Equity Incentive Plan | First Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage			25.00%
Stock options | 2011 Equity Incentive Plan | Remaining Period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			36 months
Stock options | 2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period			10 years
Award vesting period			4 years
Stock options | 2019 Equity Incentive Plan | First Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage			25.00%
Stock options | 2019 Equity Incentive Plan | Remaining Period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			36 months
Vesting of restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Stock-based compensation expense	23,000	$ 10,600	$ 52,000	28,000
Modification expense	$ 3,900		$ 3,900	$ 4,800
Weighted-average period of recognition			2 years 8 months 12 days
Vesting of restricted stock units | First Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Award vesting percentage			25.00%
Vesting of restricted stock units | Remaining Period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			36 months

Stockholders' Equity - Stock _2

Stockholders' Equity - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Number of Shares
Options outstanding, beginning balance (in shares)			6,963,000
Granted (in shares)	0	0	0	0
Exercised (in shares)			(1,527,000)
Cancelled/forfeited (in shares)			(261,000)
Options outstanding, ending balance (in shares)	5,175,000		5,175,000		6,963,000
Options vested and exercisable (in shares)	3,912,000		3,912,000
Options unvested and exercisable (in shares)	173,000		173,000
Stock Options Weighted Average Exercise Price
Options outstanding, weighted average exercise price, beginning of period (in USD per share)	$ 5.27		$ 5.27		$ 5.63
Granted, weighted average exercise price (in USD per share)			0
Exercised, weighted average exercise price (in USD per share)			5.96
Cancelled/forfeited, weighted average exercise price (in USD per share)			11
Options outstanding, weighted average exercise price, end of period (in USD per share)	5.27		5.27		$ 5.63
Vested and exercisable, weighted-average exercise price (in USD per share)	3.97		3.97
Unvested and exercisable, weighted-average exercise price (in USD per share)	$ 6.65		$ 6.65
Stock Option Activity, Additional Disclosures
Weighted-average remaining contractual period			5 years 2 months 12 days		6 years 8 months 12 days
Vested and exercisable, weighted average contractual term			4 years 7 months 6 days
Unvested and exercisable, weighted average contractual term			7 years 1 month 6 days
Aggregate intrinsic value	$ 182,027		$ 182,027		$ 569,094
Vested and exercisable, aggregate intrinsic value	142,675		142,675
Unvested and exercisable, aggregate intrinsic value	$ 5,841		$ 5,841

Stockholders' Equity - Early Ex

Stockholders' Equity - Early Exercise of Stock Options (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares (in shares)	47,882	90,977
Number of Shares
Beginning balance (in shares)	90,977
Ending balance (in shares)	47,882
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares (in shares)	48,000	91,000
Other long-term liabilities	$ 0.2	$ 0.4
Number of Shares
Beginning balance (in shares)	91,000
Early exercise of options (in shares)	0
Vested (in shares)	(43,000)
Repurchased (in shares)	0
Ending balance (in shares)	48,000

Stockholders' Equity - RSUs and

Stockholders' Equity - RSUs and Revest Shares (Details) $ in Thousands	Oct. 01, 2020cofoundershares	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 36,636	$ 12,142	$ 100,900	$ 34,752
Modification expense		2,400	400	$ 3,700	400
Signal Sciences Corp.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of cofounders with shares subject to revesting | cofounder	3
Shares held back for restricted stock awards, revesting period	2 years
Signal Sciences Corp. | Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares restricted for stock awards (in shares) | shares	896,499
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Stock-based compensation expense		23,000	$ 10,600	$ 52,000	28,000
Modification expense		3,900		3,900	$ 4,800
Unrecognized stock-based compensation cost		176,600		$ 176,600
Weighted-average period of recognition				2 years 8 months 12 days
RSUs | First Year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Award vesting percentage				25.00%
RSUs | Remaining Period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				36 months
Revest Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		11,000		$ 32,900
Unrecognized stock-based compensation cost		$ 43,900		$ 43,900
Weighted-average period of recognition				1 year

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Restricted, Revest, and Performance Shares (Details) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
RSUs
Number of Shares
Beginning balance (in shares)	4,520,000
Granted (in shares)	1,890,000
Vested (in shares)	(1,463,000)
Cancelled/forfeited (in shares)	(470,000)
Ending balance (in shares)	4,477,000	4,520,000
Weighted-Average  Grant Date Fair Value Per Share
Beginning balance (in USD per share)	$ 30.01
Granted (in USD per share)	63.95
Vested (in USD per share)	33.52
Forfeited (in USD per share)	42.78
Ending balance (in USD per share)	$ 41.85	$ 30.01
Revest Shares
Number of Shares
Beginning balance (in shares)	784,000
Vested (in shares)	(336,000)
Cancelled/forfeited (in shares)	0
Ending balance (in shares)	448,000	784,000
Weighted-Average  Grant Date Fair Value Per Share
Beginning balance (in USD per share)	$ 97.84
Vested (in USD per share)	97.84
Forfeited (in USD per share)
Ending balance (in USD per share)	$ 97.84	$ 97.84
PSUs
Number of Shares
Beginning balance (in shares)	88,000
Granted (in shares)	71,000	75,828
Vested (in shares)	(57,000)
Cancelled/forfeited (in shares)	(12,000)	(12,090)
Ending balance (in shares)	90,000	88,000
Weighted-Average  Grant Date Fair Value Per Share
Beginning balance (in USD per share)	$ 65.11
Granted (in USD per share)	102.06
Vested (in USD per share)	44.25
Forfeited (in USD per share)	44.25
Ending balance (in USD per share)	$ 110.29	$ 65.11

Stockholders' Equity - Performa

Stockholders' Equity - Performance-Based Restricted Stock Units (PSUs) (Details)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 28, 2021installmentshares	Mar. 31, 2020shares	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)shares	Sep. 30, 2020USD ($)	Dec. 31, 2020shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Modification expense | $			$ 2,400,000	$ 400,000	$ 3,700,000	$ 400,000
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) | shares					71,000		75,828
Shares issued for each PSU, ratio	1	1
Award vesting percentage		25.00%
Actual performance percentage							172.00%
Shares cancelled (in shares) | shares					12,000		12,090
Stock-based compensation expense | $			(500,000)	$ 0	$ 3,800,000	0
Unrecognized stock-based compensation cost | $			4,700,000		$ 4,700,000
Weighted-average period of recognition					2 years 8 months 12 days
PSUs | Performance Target One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target performance percentage	90.00%	90.00%
Award vesting percentage	50.00%	50.00%
PSUs | Performance Target Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target performance percentage	100.00%	100.00%
Award vesting percentage	100.00%	100.00%
PSUs | Performance Target Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target performance percentage	110.00%	110.00%
Award vesting percentage	150.00%	200.00%
PSUs | First Installment
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	25.00%
PSUs | Remaining Installments
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	6.25%
Number of vesting installments | installment	12
PSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) | shares	70,680	87,918
Target performance percentage	150.00%	200.00%
Revest Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares cancelled (in shares) | shares					0
Unrecognized stock-based compensation cost | $			43,900,000		$ 43,900,000
Weighted-average period of recognition					1 year
Vesting of restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares) | shares					1,890,000
Shares cancelled (in shares) | shares					470,000
Unrecognized stock-based compensation cost | $			176,600,000		$ 176,600,000
Modification expense | $			$ 3,900,000		$ 3,900,000	$ 4,800,000
Weighted-average period of recognition					2 years 8 months 12 days
Vesting of restricted stock units | Performance Target One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage					25.00%

Stockholders' Equity - ESPP (De

Stockholders' Equity - ESPP (Details) - USD ($) $ in Thousands, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contributions withheld for taxes	$ 3,500	$ 2,000	$ 6,000	$ 6,100
Stock-based compensation expense	36,636	12,142	$ 100,900	$ 34,752
Stock repurchased during period (in shares)			0.2	0.2
Shares issuable pursuant to the ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum employee contribution as a percentage of salary			15.00%
Offering period duration			6 months
Purchase price of common stock, percent			85.00%
Stock-based compensation expense	$ 600	$ 400	$ 2,700	$ 2,300

Stockholders' Equity - Fair Val

Stockholders' Equity - Fair Value Assumptions - ESPP (Details) - Shares issuable pursuant to the ESPP - $ / shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		6 months
Risk-free interest rate, minimum	0.02%	0.14%
Risk-free interest rate, maximum	0.10%	1.59%
Expected volatility, minimum	47.00%	43.00%
Expected volatility, maximum	50.00%	60.00%
Dividend yield	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of common stock (in dollars per share)	$ 12.66	$ 6.02
Expected term (in years)	5 months 26 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of common stock (in dollars per share)	$ 24.07	$ 14.09
Expected term (in years)	6 months

Stockholders' Equity - Stock-ba

Stockholders' Equity - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 36,636	$ 12,142	$ 100,900	$ 34,752
Share-based payment arrangement, amount capitalized	2,600	600	3,411	1,238
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,897	929	4,911	2,634
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	14,752	4,371	31,344	10,095
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	9,121	3,194	19,760	11,753
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 10,866	$ 3,648	$ 44,885	$ 10,270

Stockholders' Equity - Common_2

Stockholders' Equity - Common Stock Warrant Liabilities (Details) - shares	May 21, 2019	Sep. 30, 2020	Sep. 30, 2020
Common Class B
Class of Stock [Line Items]
Conversion of stock (in shares)	53,600,000	0	144,635,000

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Narrative (Details)	Sep. 30, 2021vote	May 31, 2019vote
Common Class A
Class of Stock [Line Items]
Common stock, voting rights (votes per share)	1	1
Common Class B
Class of Stock [Line Items]
Common stock, voting rights (votes per share)	10	10
Common Class B | Conversion Of Class B Common Stock To Class A Common Stock
Class of Stock [Line Items]
Common stock, conversion ratio	1

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Computation of EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	May 21, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Class of Stock [Line Items]
Weighted-average shares used in computing net loss per share attributable to common stockholder, basic (in shares)		116,475,000	105,942,000	115,320,000	100,413,000
Weighted-average shares used in computing net loss per share attributable to common stockholder, diluted (in shares)		116,475,000	105,942,000	115,320,000	100,413,000
Net loss per share attributable to common stockholders, basic (in US dollar per share)		$ (0.48)	$ (0.22)	$ (1.43)	$ (0.50)
Net loss per share attributable to common stockholders, diluted (in US dollar per share)		$ (0.48)	$ (0.22)	$ (1.43)	$ (0.50)
Common Class A
Class of Stock [Line Items]
Net loss attributable to common stockholders		$ (55,109)	$ (20,763)	$ (154,623)	$ (39,670)
Weighted-average shares used in computing net loss per share attributable to common stockholder, basic (in shares)		114,218,000	92,510,000	107,952,000	79,307,000
Weighted-average shares used in computing net loss per share attributable to common stockholder, diluted (in shares)		114,218,000	92,510,000	107,952,000	79,307,000
Net loss per share attributable to common stockholders, basic (in US dollar per share)		$ (0.48)	$ (0.22)	$ (1.43)	$ (0.50)
Net loss per share attributable to common stockholders, diluted (in US dollar per share)		$ (0.48)	$ (0.22)	$ (1.43)	$ (0.50)
Common Class A | IPO
Class of Stock [Line Items]
Shares issued (in shares)	12,900,000
Common Class B
Class of Stock [Line Items]
Net loss attributable to common stockholders		$ (1,089)	$ (3,015)	$ (10,553)	$ (10,558)
Weighted-average shares used in computing net loss per share attributable to common stockholder, basic (in shares)		2,257,000	13,432,000	7,368,000	21,106,000
Weighted-average shares used in computing net loss per share attributable to common stockholder, diluted (in shares)		2,257,000	13,432,000	7,368,000	21,106,000
Net loss per share attributable to common stockholders, basic (in US dollar per share)		$ (0.48)	$ (0.22)	$ (1.43)	$ (0.50)
Net loss per share attributable to common stockholders, diluted (in US dollar per share)		$ (0.48)	$ (0.22)	$ (1.43)	$ (0.50)
Number of shares converted (in shares)	53,600,000		0		144,635,000

Net Loss Per Share Attributab_5

Net Loss Per Share Attributable to Common Stockholders - Antidilutive Securities (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	19,550	11,928
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	5,175	7,290
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	4,458	4,354
PSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	109	88
Revest shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	448	0
Early exercised stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	48	106
Shares issuable pursuant to the ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	83	90
Convertible senior notes (if-converted)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	9,229	0

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 30	$ 336	$ 44	$ 1,131

Information About Revenue and_3

Information About Revenue and Geographic Areas (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)segment	Dec. 31, 2020USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment	1
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 147,729	$ 95,979
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	114,130	65,054
All other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 33,599	$ 30,925