Nextdoor (KIND) 10-K 15 Mar 22 2021 FY Annual report Financial data

Cover

Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 11, 2022	Jun. 30, 2021
Entity Information [Line Items]
Amendment Flag	false
Entity Central Index Key	0001846069
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-40246
Entity Registrant Name	Nextdoor Holdings, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	86-1776836
Entity Address, Address Line One	420 Taylor Street
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94102
City Area Code	(415)
Local Phone Number	344-0333
Title of 12(b) Security	Class A common stock, par value $0.0001 per share
Trading Symbol	KIND
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 413.9
Documents Incorporated by Reference	Information required in responses to Part III of Form 10-K is hereby incorporated by reference to portions of the Registrant’s Proxy Statement for the Annual Meeting of Stockholders to be held in 2022. The Proxy Statement will be filed by the Registrant with the Securities and Exchange Commission no later than 120 days after the end of the Registrant’s fiscal year ended December 31, 2021.
Class A Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		79,007,124
Class B Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		307,024,318

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Audit Information [Abstract]
Auditor Name	Ernst & Young LLP
Auditor Location	Redwood City, California
Auditor Firm ID	42

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 521,812	$ 83,642
Marketable securities	193,999	53,341
Accounts receivable, net of allowance of $425 and $313 as of December 31, 2021 and 2020, respectively	29,673	21,818
Prepaid expenses and other current assets	16,259	5,453
Restricted cash, current	0	1,101
Total current assets	761,743	165,355
Property and equipment, net	12,545	5,718
Operating lease right-of-use assets	59,422	37,776
Intangible assets, net	4,835	6,987
Goodwill	1,211	1,211
Other assets	330	700
Total assets	840,086	217,747
Current liabilities:
Accounts payable	6,163	3,354
Operating lease liabilities, current	7,131	3,348
Liability for unvested restricted stock	4,765	10,483
Accrued expenses and other current liabilities	15,444	14,998
Total current liabilities	33,503	32,183
Operating lease liabilities, non-current	61,598	36,254
Total liabilities	95,101	68,437
Commitments and contingencies (Note 9)
Redeemable convertible preferred stock		447,166
Stockholders' equity (deficit):
Additional paid-in capital	1,225,815	87,945
Accumulated other comprehensive loss	(529)	(797)
Accumulated deficit	(480,339)	(385,014)
Total stockholders' equity (deficit)	744,985	(297,856)
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	840,086	217,747
Class A Common Stock
Stockholders' equity (deficit):
Common stock	8	0
Class B Common Stock
Stockholders' equity (deficit):
Common stock	$ 30	$ 10

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts receivable, allowance for credit loss	$ 425	$ 313
Redeemable convertible preferred stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock authorized (in shares)	0	190,477,000
Redeemable convertible preferred stock issued (in shares)	0	190,477,000
Redeemable convertible preferred stock outstanding (in shares)	0	190,477,000	[1]
Redeemable convertible preferred stock, aggregate liquidation preference		$ 447,890
Common stock authorized (in shares)		375,788,212
Class A Common Stock
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	2,500,000,000	0
Common stock issued (in shares)	78,954,000	0
Common stock outstanding (in shares)	78,954,000	0
Class B Common Stock
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	500,000,000	375,788,000
Common stock issued (in shares)	304,701,000	103,777,000
Common stock outstanding (in shares)	304,701,000	103,777,000
[1]	The shares of the Company’s common and redeemable convertible preferred stock prior to the Reverse Recapitalization (as defined in Note 1) have been retroactively restated to reflect the exchange ratio of 3.1057 established in the Merger Agreement as described in Note 3.

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Revenue	$ 192,197	$ 123,284
Costs and expenses:
Cost of revenue	28,813	21,586
Research and development	97,096	69,231
Sales and marketing	106,430	80,325
General and administrative	54,664	28,793
Total costs and expenses	287,003	199,935
Loss from operations	(94,806)	(76,651)
Interest income	177	727
Other income (expense), net	(539)	817
Loss before income taxes	(95,168)	(75,107)
Provision for income taxes	157	127
Net loss	$ (95,325)	$ (75,234)
Net loss per share attributable to common stockholders, basic (in USD per share)	$ (0.65)	$ (0.83)
Net loss per share attributable to common stockholders, diluted (in USD per share)	$ (0.65)	$ (0.83)
Weighted average shares used in computing net loss per share attributable to common stockholders, basic (in shares)	146,337	90,190
Weighted average shares used in computing net loss per share attributable to common stockholders, diluted (in shares)	146,337	90,190

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (95,325)	$ (75,234)
Other comprehensive income (loss):
Foreign currency translation adjustments	283	(796)
Change in unrealized loss on available-for-sale marketable securities	(15)	(36)
Total other comprehensive income (loss)	268	(832)
Comprehensive loss	$ (95,057)	$ (76,066)

CONSOLIDATED STATEMENTS OF REDE

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) shares in Thousands, $ in Thousands		Total	Common StockClass A Common Stock	Common StockClass B Common Stock		Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at beginning of period (in shares) at Dec. 31, 2019	[1]	190,477
Balance at beginning of period at Dec. 31, 2019		$ 447,166
Balance at end of period (in shares) at Dec. 31, 2020	[1]	190,477
Balance at end of period at Dec. 31, 2020		$ 447,166
Balance at beginning of period (in shares) at Dec. 31, 2019			0	97,777	[1]
Balance at beginning of period at Dec. 31, 2019		(257,296)	$ 0	$ 10		$ 52,439	$ 35	$ (309,780)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of repurchases of unvested common stock (in shares)	[1]			6,801
Issuance of common stock upon exercise of stock options, net of repurchases of unvested common stock		6,367				6,367
Cancellation of restricted stock and unvested common stock issued in connection with acquisition (in shares)	[1]			(801)
Release of holdback stock in connection with acquisition		291				291
Vesting of early exercised stock options		522				522
Vesting of restricted stock		5,718				5,718
Stock-based compensation		22,608				22,608
Other comprehensive income (loss)		(832)					(832)
Net loss		(75,234)						(75,234)
Balance at end of period (in shares) at Dec. 31, 2020			0	103,777	[1]
Balance at end of period at Dec. 31, 2020		$ (297,856)	$ 0	$ 10		87,945	(797)	(385,014)
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of redeemable convertible preferred stock into Class B common stock in connection with the Reverse Recapitalization (in shares)	[1]	(190,477)
Conversion of redeemable convertible preferred stock into Class B common stock in connection with the Reverse Recapitalization		$ (447,166)
Balance at end of period (in shares) at Dec. 31, 2021		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of redeemable convertible preferred stock into Class B common stock in connection with the Reverse Recapitalization (in shares)	[1]			190,477
Conversion of redeemable convertible preferred stock into Class B common stock in connection with the Reverse Recapitalization		$ 447,166		$ 19		447,147
Issuance of common stock upon the Reverse Recapitalization, net of issuance costs (in shares)			78,954
Issuance of common stock upon the Reverse Recapitalization, net of issuance costs		622,588	$ 8			622,580
Release of restricted stock units (in shares)	[1]			101
Tax withholdings on release of restricted stock units		$ (863)				(863)
Issuance of common stock upon exercise of stock options, net of repurchases of unvested common stock (in shares)		10,325		10,325	[1]
Issuance of common stock upon exercise of stock options, net of repurchases of unvested common stock		$ 15,334		$ 1		15,333
Issuance of common stock in connection with acquisition (in shares)	[1]			21
Vesting of early exercised stock options		442				442
Vesting of restricted stock		5,717				5,717
Stock-based compensation		47,514				47,514
Other comprehensive income (loss)		268					268
Net loss		(95,325)						(95,325)
Balance at end of period (in shares) at Dec. 31, 2021			78,954	304,701	[1]
Balance at end of period at Dec. 31, 2021		$ 744,985	$ 8	$ 30		$ 1,225,815	$ (529)	$ (480,339)
[1]	The shares of the Company’s common and redeemable convertible preferred stock prior to the Reverse Recapitalization (as defined in Note 1) have been retroactively restated to reflect the exchange ratio of 3.1057 established in the Merger Agreement as described in Note 3.

CONSOLIDATED STATEMENTS OF RE_2

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) (Parenthetical)	Dec. 31, 2021
Recapitalization exchange ratio	3.1057
Class B Common Stock
Recapitalization exchange ratio	3.1057

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (95,325)	$ (75,234)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,172	3,058
Stock-based compensation	47,514	22,608
Bad debt expense	317	291
Other	3	239
Changes in operating assets and liabilities:
Accounts receivable, net	(8,172)	(3,173)
Prepaid expenses and other current assets	(4,087)	2,472
Operating lease right-of-use assets	6,605	5,181
Other assets	370	(221)
Accounts payable	2,759	15
Operating lease liabilities	(5,844)	(4,529)
Accrued expenses and other current liabilities	420	7,689
Net cash used in operating activities	(51,268)	(41,604)
Cash flows from investing activities:
Purchases of property and equipment	(8,846)	(5,023)
Purchases of marketable securities	(199,832)	(77,600)
Sales of marketable securities	2,411	21,826
Maturities of marketable securities	56,745	97,589
Net cash provided by (used in) investing activities	(149,522)	36,792
Cash flows from financing activities:
Proceeds from exercise of stock options, net of repurchases	15,334	6,367
Proceeds from the Reverse Recapitalization	628,489	0
Payment of transaction costs related to the Reverse Recapitalization	(5,384)	0
Tax withholdings on release of restricted stock units	(863)	0
Net cash provided by financing activities	637,576	6,367
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	283	(796)
Net increase in cash, cash equivalents, and restricted cash	437,069	759
Cash, cash equivalents, and restricted cash at beginning of period	84,743	83,984
Cash, cash equivalents, and restricted cash at end of period	521,812	84,743
Reconciliation of cash, cash equivalents, and restricted cash to the consolidated balance sheets:
Cash and cash equivalents	521,812	83,642
Restricted cash	0	1,101
Total cash, cash equivalents, and restricted cash	521,812	84,743
Supplemental cash flow disclosures:
Cash paid for taxes	313	30
Non-cash investing and financing activities:
Vesting of restricted stock and early exercised stock options	6,159	6,240
Lease liabilities arising from obtaining right-of-use assets	34,971	40,790
Unpaid deferred transaction costs	314	0
Conversion of redeemable convertible preferred stock into Class B common stock in connection with the Reverse Recapitalization	$ 447,166	$ 0

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Nextdoor Holdings, Inc. (“Nextdoor” or the “Company”) is headquartered in San Francisco, California. Nextdoor’s purpose is to cultivate a kinder world where everyone has a neighborhood they can rely on. That purpose enables the Company’s mission to be the neighborhood hub for trusted connections and the exchange of helpful information, goods, and services. On November 5, 2021 (the “Closing”), the Company consummated the transactions contemplated by the Agreement and Plan of Merger, dated July 6, 2021, as amended on September 30, 2021 (the “Merger Agreement”), by and among Khosla Ventures Acquisition Co. II (“KVSB”), a special purpose acquisition company, Lorelei Merger Sub Inc. (“Merger Sub”), and Nextdoor, Inc. (“Legacy Nextdoor”), with Legacy Nextdoor surviving as a wholly owned subsidiary of KVSB (the “Merger” and, collectively with the other transactions that occurred in connection with the Merger, including the PIPE Investment (as described in Note 3, the “Reverse Recapitalization”). In connection with the Closing, KVSB was renamed to Nextdoor Holdings, Inc. Reported results from operations included herein prior to the Reverse Recapitalization are those of Legacy Nextdoor. See Note 3 - Reverse Recapitalization for further details.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company’s fiscal year ends on December 31. The Merger was accounted for as a reverse recapitalization in accordance with GAAP. This determination was primarily based on the evaluation of the following facts and circumstances: • Legacy Nextdoor stockholders had a relative majority of the voting power of Nextdoor; • The Board of Directors of Nextdoor had ten members, and Legacy Nextdoor stockholders had the ability to nominate a majority of the members of the Board of Directors; • Legacy Nextdoor’s senior management comprised the senior management roles of Nextdoor and were responsible for the day-to-day operations; • Nextdoor assumed the Nextdoor Holdings, Inc. name and Legacy Nextdoor’s corporate headquarters; and • The intended strategy and operations of Nextdoor continued Legacy Nextdoor’s strategy and operations to leverage technology to connect millions of neighbors online and in real life to build stronger, more vibrant, and resilient neighborhoods. Under this method of accounting, KVSB was treated as the “acquired” company for financial reporting purposes. Accordingly, the financial statements of Nextdoor represent the continuation of the financial statements of Legacy Nextdoor, with the Merger reflected as the equivalent of Nextdoor issuing common stock for the net assets of KVSB, accompanied by a recapitalization. The shares and corresponding capital amounts and all per share data related to Legacy Nextdoor’s outstanding redeemable convertible preferred stock, common stock, and stock-based awards prior to the Reverse Recapitalization have been retroactively adjusted using the Exchange Ratio (as defined in Note 3). The conversion of the outstanding shares of Legacy Nextdoor redeemable convertible preferred stock into shares of Class B common stock in connection with the Reverse Recapitalization and the issuance of Class A common stock are presented as of the Closing of the Merger in the consolidated statements of redeemable convertible preferred stock and stockholders’ equity (deficit). The net assets of KVSB were recognized as of the Closing at historical cost, with no goodwill or other intangible assets recorded. Operations prior to the Merger are those of Legacy Nextdoor and Legacy Nextdoor’s operations are the only ongoing operations of Nextdoor. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Estimates include, but are not limited to, valuation of financial instruments, valuation of common stock through the date of the Reverse Recapitalization, valuation of stock-based awards, revenue recognition, collectability of accounts receivable, valuation of acquired intangible assets and goodwill, useful lives of intangible assets, useful lives of property and equipment, the incremental borrowing rate applied in lease accounting, income taxes and deferred income tax assets and associated valuation allowances. The Company bases these estimates and assumptions on historical experience and various other assumptions that it considers reasonable. The actual results could differ materially from these estimates. Foreign Currency The functional currency of the Company’s international subsidiaries is generally their local currency. The financial statements of these subsidiaries are translated into U.S. dollars using month-end exchange rates for assets and liabilities, historical exchange rates for equity, and average exchange rates for revenue and expenses. Translation gains and losses are recorded in accumulated other comprehensive income (loss) as a component of stockholders’ equity (deficit). Unrealized foreign exchange gains and losses due to the re-measurement of monetary assets and liabilities denominated in non-functional currencies and realized foreign exchange gains and losses on foreign exchange transactions are recorded in other income (expense), net in the consolidated statements of operations. Cash and Cash Equivalents Cash and cash equivalents consist of highly liquid investments with insignificant interest rate risk and original maturities of three months or less at the time of purchase. Cash and cash equivalents include demand deposits and money market accounts. Interest is accrued as earned. Cash and cash equivalents are recorded at cost, which approximates fair value. Marketable Securities The Company’s marketable securities are comprised of commercial paper, corporate securities, U.S. Treasury securities, and asset-backed securities. The Company determines the appropriate classification of its investments at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its investments as available-for-sale securities as the Company may sell these securities at any time for use in its current operations or for other purposes, even prior to maturity. As a result, the Company classifies its investments, including securities with stated maturities beyond 12 months, within current assets on the consolidated balance sheets. Available-for-sale securities are recorded at fair value each reporting period. Unrealized gains and losses on these investments are reported as a separate component of accumulated other comprehensive income (loss) on the consolidated balance sheets until realized. Interest income is reported within interest income in the consolidated statements of operations. The Company periodically evaluates its marketable securities to assess whether those with unrealized loss positions are other-than-temporarily impaired. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value is less than the Company’s cost basis, the financial condition and near-term prospects of the investee. Realized gains and losses are determined based on the specific identification method and are reported in other income (expense), net in the consolidated statements of operations. If the Company determines that the decline in an investment’s fair value is other than temporary, the difference is recognized as an impairment loss in the consolidated statements of operations. The Company did not consider any of its investments to be other-than-temporarily impaired for the years ended December 31, 2021 and 2020. Fair Value Measurements The Company accounts for certain assets and liabilities at fair value, which is the expected exchange price that would be received for an asset or an exit price paid to transfer a liability in an orderly transaction between market participants on the measurement date. Assets and liabilities measured at fair value are classified into the following categories based on the degree to which the inputs the Company uses to measure the fair values are observable in active markets. The Company uses the most observable inputs available when measuring fair value. • Level 1: Observable inputs such as unadjusted quoted prices for identical assets or liabilities in active markets; • Level 2: Observable inputs such as quoted prices for similar assets or liabilities in active markets, quoted prices for identical assets or liabilities in inactive markets, or inputs that are derived principally from or corroborated by observable market data or other means; and • Level 3: Unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Accounts Receivable and Allowance for Doubtful Accounts The Company records accounts receivable at the original invoiced amount. The Company maintains an allowance for doubtful accounts for any receivables it may be unable to collect and reduces the allowance when it determines that it will be unable to collect specific receivables. The Company determines the allowance based on its receivables’ age, the customers’ credit quality, and current economic conditions, among other factors that may affect the customers’ ability to pay. Restricted Cash The Company’s restricted cash balance is primarily invested in a savings account and pledged as collateral for standby letters of credit as security deposits for the Company’s office leases. As of December 31, 2021 and 2020, the Company had restricted cash balances of $0 million and $1.1 million, respectively. Property and Equipment Property and equipment are recorded at cost, less accumulated depreciation and amortization. Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets as follows: Estimated Useful Life Computer equipment and software 3 years Furniture and fixtures 5 years Leasehold improvements Shorter of the estimated useful life of 5 years or the lease term Maintenance and repair costs are expensed as incurred. Capitalized Internal-use Software The Company capitalizes internal-use software costs when preliminary development efforts are successfully completed, management has authorized and committed project funding, and it is probable that the project will be completed, and the software will be used as intended. Costs related to preliminary project activities and post-implementation activities are expensed as incurred and costs related to the application development stage are capitalized. Capitalized costs are recorded as part of property and equipment, net. The capitalized costs related to internal-use software are amortized on a straight-line basis over an estimated useful life of two Business Combinations The Company includes the results of operations of the businesses that it acquires from the date of acquisition. The Company accounts for its acquisitions using the acquisition method of accounting. The Company allocates the fair value of purchase consideration to the tangible assets acquired, liabilities assumed, and intangible assets acquired, based on their estimated fair values. The excess of the fair value of purchase consideration over the values of these identifiable assets and liabilities is recorded as goodwill. When determining the fair value of assets acquired and liabilities assumed, management makes significant estimates and assumptions, especially with respect to intangible assets. Significant estimates in valuing certain identifiable assets include, but are not limited to, expected long-term market growth, future expected operating expenses, appropriate discount rates, and useful lives. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. Acquisition costs, such as legal and consulting fees, are expensed as incurred. During the measurement period, the Company may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon the conclusion of the measurement period, which is not to exceed one year from the acquisition date, any subsequent adjustments are recorded in the consolidated statements of operations. See Note 4 - Acquisitions for additional information regarding the Company’s acquisition. Goodwill and Other Acquired Intangible Assets Goodwill represents the excess of the purchase price over the fair value of net assets acquired in connection with business combinations accounted for using the acquisition method of accounting. Goodwill is not amortized, but is tested for impairment at least annually, in the fourth quarter, or whenever events or changes in circumstances indicate that goodwill might be impaired. For all periods presented the Company had one reporting unit. The Company’s test for goodwill impairment starts with a qualitative assessment to determine whether it is necessary to perform the quantitative goodwill impairment test. If the Company determines, based on the qualitative factors, that the fair value of the reporting unit is more likely than not to be less than the carrying amount, then a quantitative goodwill impairment test is required. There was no impairment of goodwill recorded for the years ended December 31, 2021 and 2020. Intangible assets consist of identifiable intangible assets, including customer relationships and developed technology, resulting from the Company’s acquisitions. Acquired intangible assets are recorded at cost, net of accumulated amortization. Intangible assets are amortized on a straight-line basis over their estimated useful lives. Amortization costs are recorded in sales and marketing in the consolidated statements of operations. Impairment of Long-Lived Assets Property and equipment and other long-lived assets, such as finite-lived intangible assets, subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If impairment is indicated, an impairment loss is recognized as the amount by which the carrying amount exceeds the fair value. No impairment was required for long-lived assets for the years ended December 31, 2021 and 2020. Leases Results and disclosure requirements for all periods presented are presented under ASU 2016-02, Leases (“Topic 842”). The Company has various lease agreements related to real estate that are all classified as operating leases. At the inception of the Company’s contracts it determines if the contract is or contains a lease. A contract is or contains a lease if it conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The Company has elected not to separate the lease and non-lease components within the contract. For leases that have greater than a 12-month lease term, right-of-use (“ROU”) assets and operating lease liabilities are recognized on the consolidated balance sheets at commencement date based on the present value of remaining fixed lease payments. Certain of the Company’s leases include options to extend the lease, with renewal terms that can extend the lease term from one month to five years. If the Company is reasonably certain to exercise an option to extend a lease, the extension period is included as part of the ROU asset and the operating lease liability. When the discount rate implicit in the lease cannot be readily determined, the Company uses its incremental borrowing rate at lease commencement in order to discount lease payments to present value for purposes of performing lease classification tests and measuring the lease liability. The Company’s incremental borrowing rate represents the rate of interest the Company would have to pay to borrow, on a collateralized basis, over a similar term an amount equal to the lease payments in a similar economic environment. The operating lease ROU asset also includes accrued lease expense resulting from the straight-line accounting under prior accounting methods, which is now being amortized over the remaining life of the lease. The Company’s lease payments are largely fixed. Variable lease payments exist in circumstances such as payments for property tax, insurance, and common area maintenance. Variable lease payments are recognized in operating expense in the period in which the obligation for those payments are incurred. Certain of the Company’s leases include an option to early terminate the lease. The Company’s leases may contain early termination options which may result in an early termination fee. The Company early terminated one of its leases in October 2020 and incurred an early termination fee of $0.1 million. The Company has a significant lease for its new headquarters in San Francisco, California, which does not include an option to early terminate. The first portion of the lease commenced in June 2020 and the second, and final portion of the lease, commenced in January 2021. For the Company’s leases, it has elected to not apply the recognition requirements to leases of twelve months or less. These leases are expensed on a straight-line basis and no operating lease liability will be recorded. Concentration of Credit and Customer Risks Financial instruments that are exposed to concentrations of credit risk consist principally of cash and cash equivalents, marketable securities and accounts receivable. The Company maintains cash and cash equivalents and marketable securities with domestic and foreign financial institutions and at times may exceed federally insured limits. The Company performs periodic evaluations of the relative credit standing of these institutions. The Company maintains investments in U.S. government debt and agency securities, corporate debt securities, and commercial paper that carry high credit ratings and accordingly, minimal credit risk exists with respect to these balances. One customer represented 10% or more of accounts receivable and no customer represented 10% or more of revenue as of and for the year ended December 31, 2021. No customer represented 10% or more of accounts receivable or revenue as of and for the year ended December 31, 2020. Revenue Recognition The Company generates a majority of its revenue from the delivery of advertising services. The Company determines revenue recognition through the following steps: (1) Identification of the contract, or contracts, with a customer (2) Identification of the performance obligations in the contract (3) Determination of the transaction price (4) Allocation of the transaction price to the performance obligations in the contract (5) Recognition of revenue when, or as, the Company satisfies a performance obligation The Company recognizes advertising revenue after satisfying its contractual performance obligation, which, for the majority of its advertising arrangements, is when an advertising impression is displayed to users. None of the Company’s arrangements contain minimum impression guarantees. The Company typically bills advertisers on a monthly basis and the payment terms vary by customer type and location. The Company has other advertising arrangements for the sale of neighborhood sponsorship and local deals which are typically fixed-fee arrangements and revenue is recognized on a straight-line basis over the non-cancellable contractual term of the agreement, generally beginning on the date its service is made available to the customer. Deferred Revenue In certain advertising arrangements the Company requires payment upfront from its customers. The Company records deferred revenue when it collects cash from customers in advance of revenue recognition. As of December 31, 2021 and 2020, deferred revenue was $3.4 million and $2.6 million, respectively, and included within accrued expenses and other current liabilities on the consolidated balance sheets. For the years ended December 31, 2021 and 2020, revenue recognized from deferred revenue at the beginning of each year was $2.5 million and $0.7 million, respectively. Practical Expedients and Exemptions The Company expenses sales commissions as incurred because the expected period of benefit is less than one year. These costs are recorded within sales and marketing expenses in the consolidated statements of operations. The Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which it recognizes revenue at the amount to which it has the right to invoice for services performed. Cost of Revenue Cost of revenue consists primarily of expenses associated with the delivery of the Company’s revenue generating activities, including third-party costs of hosting its platform and allocated personnel-related costs, including salaries, benefits and stock-based compensation for employees engaged in development of its revenue generating products. Cost of revenue also includes third-party costs associated with delivering and supporting its advertising products and credit card transaction fees related to processing customer transactions. Research and Development Research and development expenses consist primarily of personnel-related costs, including salaries, benefits and stock-based compensation for its employees engaged in research and development, as well as costs for consultants, contractors and third-party software. In addition, allocated overhead costs, such as facilities, information technology, and depreciation are included in research and development expenses. Sales and Marketing Sales and marketing expenses consist primarily of personnel-related costs and other costs which include salaries, commissions, benefits, and stock-based compensation for employees engaged in sales and marketing activities as well as other costs including third-party consulting, public relations, allocated overhead costs, and amortization of acquired intangible assets. Sales and marketing expenses also include brand and performance marketing for both user and small and mid-sized customer acquisition, and neighbor services, which includes personnel-related costs for the Company's neighbor support team, its outsourced neighbor support function, and verification costs. General and Administrative General and administrative expenses consist primarily of personnel-related costs, including salaries, benefits, and stock-based compensation, for certain executives, finance, legal, information technology, human resources, and other administrative employees. In addition, general and administrative expenses include fees and costs for professional services, including consulting, third-party legal and accounting services, and allocated overhead costs. Advertising Costs Advertising costs which consist primarily of brand and performance marketing are expensed as incurred and are included in sales and marketing expense in the consolidated statements of operations. Total advertising costs incurred were $37.5 million and $23.7 million for the years ended December 31, 2021 and 2020, respectively. Income Taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred income taxes are recognized for differences between financial reporting and tax bases of assets and liabilities at the enacted statutory tax rates in effect for the years in which the temporary differences are expected to reverse. Management makes an assessment of the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s historical operating performance and the recorded cumulative net losses in prior fiscal periods, the U.S. net deferred tax assets have been fully offset by a valuation allowance. The Company operates in various tax jurisdictions which are subject to audit by various tax authorities. The Company recognizes a tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the financial statements from such positions are then measured based on the largest benefit that has a greater than 50% cumulative likelihood of being realized upon settlement. The Company recognizes interest and penalties related to unrecognized tax benefits in the income tax provision in the consolidated statements of operations. Net Loss Per Share Attributable to Common Stockholders The Company presents net loss per share attributable to common stockholders in conformity with the two-class method required for multiple classes of common stock and participating securities. Under the two-class method, net loss is attributed to common stockholders and participating securities based on their participation rights. The rights, including the liquidation and dividend rights, of the Class A common stock and Class B common stock are substantially identical, other than voting rights. Accordingly, the Class A common stock and Class B common stock share proportionately in the Company’s net losses. The Company considers its redeemable convertible preferred stock (prior to the Reverse Recapitalization), early exercised stock options, and unvested restricted stock to be participating securities and contractually entitles the holders of such shares to participate in dividends but does not contractually obligate the holders of such shares to participate in the Company’s losses. As such, net losses for the periods presented were not allocated to these securities. The Company computes basic net loss per share attributable to common stockholders by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, adjusted for outstanding shares that are subject to repurchase. Diluted net loss per share attributable to common stockholders is computed by giving effect to all potentially dilutive securities outstanding for the period. For periods in which the Company reports net losses, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, because all potentially dilutive securities are anti-dilutive. Stock-Based Compensation Stock-based compensation expense for stock-based awards granted to employees and non-employees is measured based on the grant date fair value of the awards and recognized in the consolidated statements of operations on a straight-line basis over the period during which services are provided in exchange for the award, generally, the vesting period of the award. The grant date fair value of stock options granted is estimated using the Black-Scholes option pricing model. Forfeitures are accounted for as they occur. Segments The Company has one reportable and operating segment. The Company’s chief operating decision maker is its Chief Executive Officer (“CEO”), who reviews financial information presented on a consolidated basis for purposes of making operating decisions, assessing financial performance, and allocating resources. See Note 14 - Geographical Information for more details on the Company’s revenue and long-lived assets by jurisdiction. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement . ASU 2018-13 changes the disclosure requirements for fair value measurement. The Company adopted this standard as of January 1, 2020, and the adoption did not have a material impact on the Company’s consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses ( Topic 326 ): Measurement of Credit Losses on Financial Instruments , and has since issued various amendments including ASU 2018-19, ASU 2019-04, and ASU 2019-05. The guidance and related amendments modify the accounting for credit losses for most financial assets and require the use of an expected loss model, replacing the currently used incurred loss method. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The new guidance will be effective for the Company beginning January 1, 2023, though early adoption is permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures. In December 2019, the FASB issued ASU 2019-12, Income Taxes – Topic 740 – Simplifying the Accounting for Income Taxes , which simplifies the accounting for income taxes by removing certain exceptions to the general principals in Topic 740. The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. The ASU is effective for fiscal years beginning after December 15, 2021, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures.

Reverse Recapitalization

Reverse Recapitalization	12 Months Ended
	Dec. 31, 2021
Reverse Recapitalization [Abstract]
Reverse Recapitalization	Reverse Recapitalization Pursuant to the Merger Agreement, as described in Note 1, Merger Sub merged with and into Legacy Nextdoor, with Legacy Nextdoor surviving the Merger. Legacy Nextdoor became a wholly owned subsidiary of KVSB and KVSB was immediately renamed Nextdoor Holdings, Inc. Upon the consummation of the Merger, the following events contemplated by the Merger Agreement occurred, based on Legacy Nextdoor’s capitalization as of November 5, 2021: • all 61,331,815 issued and outstanding shares of Legacy Nextdoor redeemable convertible preferred stock were converted into 61,331,815 shares of Legacy Nextdoor common stock at the conversion rate as calculated pursuant to Legacy Nextdoor’s certificate of incorporation; • all 97,886,321 issued and outstanding shares of Legacy Nextdoor common stock (including Legacy Nextdoor common stock resulting from the conversion of the Legacy Nextdoor redeemable convertible preferred stock) were converted into 304,003,976 shares of Nextdoor Class B common stock after giving effect to the exchange ratio of 3.1057 as calculated in accordance with the Merger Agreement (“Exchange Ratio”); • all 19,196,313 granted and outstanding unexercised Legacy Nextdoor options were converted into 59,616,898 Nextdoor options exercisable for shares of Nextdoor Class B common stock with the same terms and vesting conditions except for the number of shares exercisable and the exercise price, each of which was adjusted by the Exchange Ratio; • all 866,687 granted and outstanding unvested Legacy Nextdoor restricted stock units (“RSUs”) were converted into 2,691,577 Nextdoor RSUs for shares of Nextdoor Class B common stock with the same terms and vesting conditions except for the number of shares, which was adjusted by the Exchange Ratio; and • the entitlement to receive 58,135 shares of Legacy Nextdoor common stock pursuant to the Pixel Labs Merger Agreement converted into the right to receive 180,549 shares of Nextdoor Class B common stock, which was adjusted by the Exchange Ratio. There were 304,003,976 shares of Nextdoor Class B common stock issued and outstanding as of the Closing and Nextdoor options and RSUs covering 62,308,475 shares reserved for the potential future issuance of Nextdoor Class B common stock as of the Closing. In connection with the Closing of the Merger: • all KVSB Class B founder shares, consisting of 5,000,000 shares of KVSB Class B common stock, automatically converted into an aggregate of 7,347,249 shares of Nextdoor Class A common stock; • all KVSB Class K founder shares, consisting of 5,000,000 shares of KVSB Class K common stock, converted into an aggregate of 3,061,354 shares of Nextdoor Class A common stock; • all 1,132,688 private placement sponsor shares of KVSB Class A common stock converted into shares of Nextdoor Class A common stock on a one-to-one basis; and • 40,412,372 shares of KVSB Class A common stock held by KVSB public stockholders, net of the redemption of 1,222,040 shares of KVSB Class A common stock, converted into Nextdoor Class A common stock on a one-to-one basis. On July 6, 2021, concurrently with the execution of the Merger Agreement, KVSB entered into subscription agreements with certain investors (collectively, the “PIPE Investors”), pursuant to, and on the terms and subject to the conditions of which, the PIPE Investors subscribed for an aggregate of 27,000,000 shares of Class A common stock, which included 750,000 shares of Nextdoor Class A common stock to the KVSB sponsor and 4,500,000 shares of Nextdoor Class A common stock to certain Legacy Nextdoor stockholders, including 500,000 shares of Nextdoor Class A common stock to Nextdoor's Chief Executive Officer and President, for an aggregate purchase price of $270.0 million (the “PIPE Investment”). The PIPE Investment was consummated substantially concurrently with the Closing of the Merger. There were 78,953,663 shares of Nextdoor Class A common stock issued and outstanding as of the Closing. Each holder of shares of Class A common stock is entitled to one vote for each share of Class A common stock held on all matters submitted to a vote of stockholders and each holder of shares of Class B common stock is entitled to 10 votes for each share of Class B common stock held on all matters submitted to a vote of stockholders. The following table presents the number of shares of common stock issued and outstanding immediately following the Reverse Recapitalization: Shares KVSB Class A common stock, outstanding prior to Reverse Recapitalization 42,767,100 Less: redemption of KVSB Class A common stock (1,222,040) Conversion of KVSB Class B founder shares 7,347,249 Conversion of KVSB Class K common stock 3,061,354 Shares issued to PIPE Investors 27,000,000 Nextdoor Class A common stock 78,953,663 Conversion of Legacy Nextdoor common stock (1) 113,526,555 Conversion of Legacy Nextdoor redeemable convertible preferred stock (2) 190,477,421 Nextdoor Class B common stock 304,003,976 Total shares of common stock immediately after Reverse Recapitalization 382,957,639 (1) Upon the completion of the Reverse Recapitalization, the 36,554,506 outstanding shares of Legacy Nextdoor common stock were converted into shares of Nextdoor Class B common stock using the Exchange Ratio. (2) Upon the completion of the Reverse Recapitalization, all 61,331,815 outstanding shares of Legacy Nextdoor redeemable convertible preferred stock converted into Legacy Nextdoor common stock on a one-to-one basis, which were then converted into shares of Nextdoor Class B common stock using the Exchange Ratio. KVSB was treated as the “acquired” company for financial reporting purposes. Accordingly, the financial statements of Nextdoor represent the continuation of the financial statements of Legacy Nextdoor, with the Merger reflected as the equivalent of Nextdoor issuing common stock for the net assets of KVSB, accompanied by a recapitalization. The net assets of KVSB were recognized as of the Closing at historical cost, with no goodwill or other intangible assets recorded. Operations prior to the Merger are those of Legacy Nextdoor and Legacy Nextdoor’s operations are the only ongoing operations of Nextdoor. In connection with the Reverse Recapitalization, the Company raised $628.5 million of proceeds, presented as cash flows from financing activities, which included the contribution of $416.4 million of funds held in KVSB’s trust account, $0.2 million of cash held in KVSB’s operating cash account, and $270.0 million of proceeds from the PIPE Investment, net of $12.2 million paid to redeem 1,222,040 public shares of KVSB’s Class A common stock and $45.9 million in transaction costs incurred by KVSB. Legacy Nextdoor incurred $5.7 million of transaction costs, which consisted of direct incremental legal, accounting, consulting, and other fees which were recorded as deferred transaction costs and upon completion of the Reverse Recapitalization were reclassified to additional paid-in capital as a reduction of the net proceeds received. The following table reconciles the elements of the Reverse Recapitalization to the consolidated statements of cash flows and the consolidated statements of redeemable convertible preferred stock and stockholders' equity (deficit) (in thousands): Year Ended December 31, 2021 Funds held in KVSB's trust account $ 416,359 Funds held in KVSB's operating cash account 194 Proceeds from the PIPE Investment 270,000 Less: amount paid to redeem public shares of KVSB's Class A common stock (12,221) Less: transaction costs incurred by KVSB (45,843) Proceeds from the Reverse Recapitalization 628,489 Less: non-cash liabilities assumed from KVSB (203) Less: unpaid deferred transaction costs (314) Less: payment of transaction costs related to the Reverse Recapitalization (5,384) Net cash from issuance of common stock upon the Reverse Recapitalization, net of issuance costs $ 622,588 The shares and corresponding capital amounts and all per share data related to Legacy Nextdoor’s outstanding redeemable convertible preferred stock, common stock, and stock-based awards prior to the Reverse Recapitalization have been retroactively adjusted using the Exchange Ratio.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2021
Business Combination and Asset Acquisition [Abstract]
Acquisitions	Acquisitions Pixel Labs, Inc. Business Combination On August 22, 2019 the Company executed a merger agreement to acquire the assets and liabilities of Pixel Labs, Inc. (“Pixel Labs”). The acquisition closed on August 27, 2019. The purchase accounting was completed in 2019 and no measurement period adjustments were recorded. The aggregate purchase consideration of $7.6 million included a time-based cash and share holdback of $0.7 million and $0.2 million, respectively, to be paid at a future date. In November 2020 final settlement of the holdback was completed.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Cash Equivalents and Marketable Securities	Cash Equivalents and Marketable Securities The amortized costs, unrealized gains and losses, and estimated fair values of the Company’s cash equivalents and marketable securities were as follows (in thousands): As of December 31, 2021 Amortized Unrealized Unrealized Estimated Cash equivalents: Money market funds $ 474,294 $ — $ — $ 474,294 Marketable securities: Commercial paper 83,728 — — 83,728 Corporate securities 78,353 24 (14) 78,363 U.S. Treasury securities 15,200 — (12) 15,188 Asset-backed securities 16,735 — (15) 16,720 Total marketable securities 194,016 24 (41) 193,999 Total $ 668,310 $ 24 $ (41) $ 668,293 As of December 31, 2020 Amortized Unrealized Unrealized Estimated Cash equivalents: Money market funds $ 28,371 $ — $ — $ 28,371 Marketable securities: Commercial paper 27,473 — — 27,473 Corporate securities 6,940 — (2) 6,938 U.S. Treasury securities 16,157 1 — 16,158 Asset-backed securities 2,772 — — 2,772 Total marketable securities 53,342 1 (2) 53,341 Total $ 81,713 $ 1 $ (2) $ 81,712 All marketable securities are designated as available-for-sale securities as of December 31, 2021 and 2020. The following tables present the contractual maturities of the Company’s marketable securities (in thousands): As of December 31, 2021 Amortized Cost Estimated Fair Value Due within one year $ 137,077 $ 137,043 Due after one to four years 56,939 56,956 Total $ 194,016 $ 193,999 As of December 31, 2020 Amortized Cost Estimated Fair Value Due within one year $ 53,342 $ 53,341

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company’s financial assets and liabilities measured at fair value on a recurring basis are classified by level within the fair value hierarchy. There were no financial assets or liabilities measured using Level 3 inputs as of December 31, 2021 and 2020. The following table presents information about the Company’s financial assets that are measured at fair value on a recurring basis (in thousands): Fair Value Measurement as of December 31, 2021 Level 1 Level 2 Total Assets: Cash equivalents: Money market funds $ 474,294 $ — $ 474,294 Marketable securities: Commercial paper — 83,728 83,728 Corporate securities — 78,363 78,363 U.S. Treasury securities — 15,188 15,188 Asset-backed securities — 16,720 16,720 Total marketable securities — 193,999 193,999 Total cash equivalents and marketable securities $ 474,294 $ 193,999 $ 668,293 Fair Value Measurement as of December 31, 2020 Level 1 Level 2 Total Assets: Cash equivalents: Money market funds $ 28,371 $ — $ 28,371 Marketable securities: Commercial paper — 27,473 27,473 Corporate securities — 6,938 6,938 U.S. Treasury securities — 16,158 16,158 Asset-backed securities — 2,772 2,772 Total marketable securities — 53,341 53,341 Total cash equivalents and marketable securities $ 28,371 $ 53,341 $ 81,712 The Company classifies its cash equivalents, marketable securities, and restricted cash within Level 1 or Level 2 because it determines their fair values using quoted market prices or alternative pricing sources and models utilizing market observable inputs. There were no transfers between levels of the fair value hierarchy during the years ended December 31, 2021 and 2020. Assets and Liabilities Measured at Fair Value on a Recurring Basis

Other Balance Sheet Components

Other Balance Sheet Components	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Other Balance Sheet Components	Other Balance Sheet Components Property and Equipment, net Property and equipment, net consisted of the following (in thousands): As of December 31, 2021 2020 Computer equipment and software $ 3,123 $ 2,002 Furniture and fixtures 2,201 1,174 Capitalized internal-use software 1,842 1,842 Leasehold improvements 9,502 2,850 Property and equipment, gross 16,668 7,868 Less: accumulated depreciation and amortization (4,123) (2,150) Property and equipment, net $ 12,545 $ 5,718 Depreciation and amortization expense was $2.0 million and $1.0 million, for the years ended December 31, 2021 and 2020, respectively. Intangible Assets, net The Company’s intangible assets consist of customer relationships and developed technology arising from acquisitions. Intangible assets, net consisted of the following (in thousands): As of December 31, 2021 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Remaining Life (years) Customer relationships $ 7,068 $ (4,684) $ 2,384 3.0 Developed technology 4,600 (2,149) 2,451 2.7 Total intangible assets, net $ 11,668 $ (6,833) $ 4,835 2.8 As of December 31, 2020 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Remaining Life (years) Customer relationships $ 7,068 $ (3,451) $ 3,617 3.0 Developed technology 4,600 (1,230) 3,370 3.7 Total intangible assets, net $ 11,668 $ (4,681) $ 6,987 3.3 Amortization expense related to intangible assets was $2.2 million and $2.1 million for the years ended December 31, 2021 and 2020, respectively. Expected future amortization expense for intangible assets as of December 31, 2021 was as follows (in thousands): Years Ending December 31, Amount 2022 $ 1,773 2023 1,773 2024 1,054 2025 235 Thereafter — Total $ 4,835 Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): As of December 31, 2021 2020 Accrued compensation $ 3,375 $ 6,888 Liability for early exercise of unvested stock options 690 1,133 Taxes payable 879 516 Deferred revenue 3,388 2,585 Other accrued and current liabilities 7,112 3,876 Accrued expenses and other current liabilities $ 15,444 $ 14,998

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	LeasesThe Company has entered into various non-cancellable office facility leases in various locations with original lease periods expiring between 2020 and 2029, with its primary office location in San Francisco, California. The Company entered into a lease consisting of multiple floors for its new San Francisco headquarters in 2019, with a lease term through 2029. The first portion of the lease commenced in June 2020, and the second and final portion of the lease commenced in January 2021. The facility lease agreements generally provide for escalating rental payments. The Company's lease agreements generally do not contain any material residual value guarantees or material restrictive covenants. The components of lease costs were as follows (in thousands): Years Ended December 31, 2021 2020 Operating lease cost $ 9,864 $ 6,278 Short-term lease cost 525 495 Variable lease cost 409 452 Total $ 10,798 $ 7,225 Other information related to the Company’s operating leases was as follows (in thousands): Years Ended December 31, 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 6,585 $ 5,624 ROU assets obtained in exchange for lease obligations: Operating leases $ 28,252 $ 39,664 Lease terms and discount rates for operating leases were as follows: As of December 31, 2021 2020 Weighted average remaining lease term (years) 7.3 8.2 Weighted average discount rate 4.5 % 5.3 % As of December 31, 2021, future minimum lease payments under operating leases were as follows (in thousands): Years Ending December 31, Amount 2022 $ 10,045 2023 10,347 2024 10,657 2025 10,977 2026 11,306 Thereafter 27,697 Total lease payments 81,029 Less: imputed interest (12,300) Present value of lease liabilities 68,729 Less: current operating lease liabilities (7,131) Long-term operating lease liabilities $ 61,598 The table above does not include lease payments that were not fixed at commencement or lease modification.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments As of December 31, 2021, the Company had non-cancellable purchase commitments with certain service providers primarily related to the provision of cloud computing services as follows (in thousands): Total Commitments Years Ending December 31, 2022 $ 18,978 2023 22,528 2024 10,417 Thereafter — Total $ 51,923 Legal matters From time to time, the Company is a party to a variety of claims, lawsuits, and proceedings which arise in the ordinary course of business, including claims of alleged infringement of intellectual property rights. The Company records a liability when it believes that it is probable that a loss will be incurred and the amount of loss or range of loss can be reasonably estimated. The Company discloses potential losses when they are reasonably possible. In the Company’s opinion, resolution of pending matters is not likely to have a material adverse impact on its consolidated results of operations, cash flows, or its financial position. Given the unpredictable nature of legal proceedings, the Company bases its estimate on the information available at the time of the assessment. As additional information becomes available, the Company reassesses the potential liability and may revise the estimate. There were no such material matters as of December 31, 2021 and 2020. Indemnification In the ordinary course of business, the Company often includes standard indemnification provisions in its arrangements with its customers, partners, suppliers, and vendors. Pursuant to these provisions, the Company may be obligated to indemnify such parties for losses or claims suffered or incurred in connection with its service, breach of representations or covenants, intellectual property infringement, or other claims made against such parties. These provisions may limit the time within which an indemnification claim can be made. It is not possible to determine the maximum potential amount under these indemnification obligations due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement. For the years ended December 31, 2021 and 2020 the Company did not incur material costs to defend lawsuits or settle claims related to these indemnifications. The Company believes the fair value of these liabilities is not material and accordingly has no liabilities recorded for these agreements as of December 31, 2021 and 2020.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit)	Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit) The shares and corresponding capital amounts and all per share data related to Legacy Nextdoor’s authorized and outstanding redeemable convertible preferred stock, common stock, and stock-based awards prior to the Reverse Recapitalization have been retroactively adjusted using the Exchange Ratio. Upon the completion of the Reverse Recapitalization on November 5, 2021, all outstanding shares of Legacy Nextdoor redeemable convertible preferred stock converted into Legacy Nextdoor common stock on a one-to-one basis, which were then converted into 190,477,421 shares of Nextdoor Class B common stock as a result of the Reverse Recapitalization, using the Exchange Ratio of 3.1057. Preferred Stock In connection with the Reverse Recapitalization, the Company's amended and restated certificate of incorporation became effective, which authorized the issuance of 50,000,000 shares of preferred stock with a par value of $0.0001 per share with such designations, voting, and other rights and preferences as may be determined from time to time by the Company's Board of Directors. As of December 31, 2021 there were no shares of preferred stock issued or outstanding. Common Stock The Company was authorized to issue 2,500,000,000 shares of Class A common stock and 500,000,000 shares of Class B common stock as of December 31, 2021 and 375,788,212 shares of common stock as of December 31, 2020. The rights, including the liquidation and dividend rights, of the Class A common stock and Class B common stock are substantially identical, other than voting and conversion rights. The holder of each share of Class A common stock is entitled to one vote per share and the holder of each share of Class B common stock is entitled to ten votes per share. Shares of Class B common stock are convertible into an equivalent number of shares of Class A common stock at the option of the holder or upon certain events upon the terms and conditions described in the Company’s amended and restated certificate of incorporation. Class A common stock and Class B common stock are referred to, collectively, as common stock throughout the notes to these consolidated financial statements, unless otherwise indicated. Shares of common stock reserved for future issuance on an as-converted basis were as follows (in thousands): As of December 31, 2021 2020 Redeemable convertible preferred stock — 190,477 Stock options outstanding 58,278 46,973 Unvested restricted stock units (RSUs) 2,511 — Shares reserved for future award issuances 77,924 12,558 Total 138,713 250,008 Common Stock Subject to Repurchase Certain stock option grant agreements permit exercise prior to vesting. Upon termination of service of an employee, the Company has the right to repurchase any unvested, but issued, common stock at the original purchase price. The consideration received for an exercise of an option is accounted for as a deposit of the exercise price and is recorded as a liability. Upon vesting of the shares pursuant to the grant agreements, the shares and related liability are reclassified into stockholders’ equity (deficit). As of December 31, 2021 and 2020, the Company had $0.7 million and $1.1 million recorded in accrued expenses and other current liabilities related to 421,594 and 692,990 unvested shares of common stock subject to repurchase, respectively. Restricted Stock Subject to Repurchase In 2018, an executive of the Company purchased 15,408,183 shares of restricted stock, subject to time-based service requirements, which vest over a forty-eight month period. The shares issued upon the purchase of restricted stock are considered to be legally issued and outstanding on the date of purchase and the executive has full voting rights. Upon termination of service, the Company may repurchase unvested shares acquired at a price equal to the price per share paid upon the exercise. Upon vesting of the shares pursuant to the grant agreements, the shares and related liability are reclassified into stockholders’ equity (deficit). As of December 31, 2021, the Company had $4.8 million recorded in deposits related to 3,210,037 unvested shares of common stock subject to repurchase. As of December 31, 2020, the Company had $10.5 million recorded in deposits related to 7,062,082 unvested shares of common stock subject to repurchase. For the years ended December 31, 2021 and 2020, the Company recorded stock-based compensation expense of $4.6 million and $4.6 million, respectively, related to this restricted stock. Equity Incentive Plans 2008 and 2018 Equity Incentive Plans In 2018, the 2008 Equity Incentive Plan (“the 2008 Plan”) was terminated, and Legacy Nextdoor’s board of directors approved the adoption of the 2018 Equity Incentive Plan (“the 2018 Plan”), which included both incentive and non-statutory stock options. The 2008 Plan and 2018 Plan (collectively, the “Legacy Equity Incentive Plans”) provided for the grant of shares of common stock to employees, directors, officers, and consultants pursuant to awards of stock options, restricted stock, or RSUs. As of December 31, 2020, the Company had reserved 4,043,637 shares of its common stock under the Legacy Equity Incentive Plans for future issuance. Options were granted at a price per share equal to the fair market value of the underlying common stock at the date of grant. Options granted generally vest over four years. RSUs granted are typically subject to a four-year vesting period and vest quarterly. While no new awards will be granted under the Legacy Equity Incentive Plans, any outstanding awards made under the Legacy Equity Incentive Plans will remain outstanding in accordance with the terms of the applicable plan and the applicable award agreements. 2021 Equity Incentive Plan In November 2021, the Company’s Board of Directors and stockholders approved the Company’s 2021 Equity Incentive Plan (the “2021 Plan”) as a successor to the Legacy Equity Incentive Plans, with the purpose of granting stock-based awards to employees, directors, officers, and consultants, including stock options, restricted stock awards, and RSUs. 2021 Employee Stock Purchase Plan In November 2021, the Company’s Board of Directors and stockholders approved the Company’s 2021 Employee Stock Purchase Plan (the “2021 ESPP”). Over a series of offering periods, each of which may consist of one or more purchase periods, eligible employees will be offered the option to purchase shares of Class A common stock at 85% of the lesser of the fair market value of Class A common stock on (i) the first business day of the applicable offering period and (ii) the date of purchase. Under the 2021 ESPP, the Company initially reserved 8,901,159 shares of Class A common stock for issuance, and the aggregate number of shares reserved will increase automatically on January 1 of each of 2022 through 2031 by the number of shares equal to the lesser of (i) one percent (1%) of the total number of outstanding shares of Class A common stock and Class B common stock as of the immediately preceding December 31, or (ii) a number of shares as may be determined by the Company’s Board of Directors. The aggregate number of shares issued over the term of the 2021 ESPP, subject to adjustments for stock-splits, recapitalizations, or similar events, may not exceed 89,011,590 shares. As of December 31, 2021, there had been no offering period or purchase period under the 2021 ESPP. Stock Options and RSUs The Company may grant options to acquire shares of Class A common stock to employees, directors, officers, and consultants at a price not less than the fair market value of the shares at the date of grant. Options granted to a person who, at the time of the grant, owns more than 10% of the voting power of all classes of stock shall be at no less than 110% of the fair market value and expire five years from the date of grant. All other options generally have a contractual term of ten years. Options granted generally vest on a monthly basis over four years. RSUs granted for Class A common stock generally vest on a quarterly basis over four years. A summary of the Company’s stock option activity for the year ended December 31, 2021 and related information is as follows (in thousands, except per share data): Number of Options Weighted- Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Balances at December 31, 2020 46,973 $ 1.80 7.8 $ 28,467 Options granted 25,262 $ 3.05 Options exercised (10,325) $ 1.48 Options forfeited or expired (3,632) $ 2.50 Balances at December 31, 2021 58,278 $ 2.35 8.1 $ 322,799 Options vested and exercisable at December 31, 2021 23,443 $ 1.72 6.6 $ 144,608 The intrinsic value is calculated as the difference between the exercise price of the underlying common stock option award and the fair value of the Company’s common stock as of the respective balance sheet date. The weighted average grant date fair value of options granted was $3.63 per share and $2.40 per share during the years ended December 31, 2021 and 2020, respectively. The total number of shares vested during the years ended December 31, 2021 and 2020 was 18,455,667 and 13,012,287, respectively. The weighted average grant-date fair value of options vested was $2.23 per share and $1.64 per share during the years ended December 31, 2021 and 2020, respectively. The intrinsic value of the options exercised was $31.9 million and $9.8 million for the years ended December 31, 2021 and 2020, respectively. The Company granted 19,639 options to non-employees during the year ended December 31, 2021. The Company did not issue any grants to non-employees during the year ended December 31, 2020. Number of Shares Weighted Average Grant Date Fair Value Unvested at December 31, 2020 — $ — RSUs granted 2,701 $ 8.74 RSUs vested (166) $ 8.91 RSUs forfeited (24) $ 7.68 Unvested at December 31, 2021 2,511 $ 8.74 Valuation Assumptions The Company’s use of the Black-Scholes option-pricing model to estimate the fair value of stock options granted requires the input of highly subjective assumptions. These assumptions were estimated as follows: Fair value of the underlying common stock – Prior to the Reverse Recapitalization, the Board of Directors considered numerous objective and subjective factors to determine the fair value of the Company’s common stock including, but not limited to: (i) the results of contemporaneous third-party valuations of the Company’s common stock; (ii) the prices, rights, preferences, and privileges of the Company’s redeemable convertible preferred stock relative to those of its common stock; (iii) the lack of marketability of the Company’s common stock; (iv) actual operating and financial results; (v) current business conditions and projections; (vi) the likelihood of achieving a liquidity event, such as an initial public offering, merger, or acquisition of the Company, given prevailing market conditions; (vii) transactions involving the Company’s shares; (viii) the history and nature of its business, industry trends and competitive environment; and (iv) general economic outlook. After the Reverse Recapitalization, the fair value of the underlying common stock is determined by the closing price, on the date of grant, of the Company’s Class A common stock, which is traded on the New York Stock Exchange. Expected volatility – Expected volatility is a measure of the amount by which the stock price is expected to fluctuate. Since the Company does not have sufficient trading history of its common stock, it estimates the expected volatility of its stock options at their grant date by taking the weighted average historical volatility of a group of comparable publicly traded companies over a period equal to the expected term of the options. Expected term – The Company determines the expected term based on the average period the stock options are expected to remain outstanding using the simplified method, calculated as the midpoint of the stock options’ vesting term and contractual expiration period, as the Company does not have sufficient historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior. Risk-free rate – The Company uses the U.S. Treasury yield for its risk-free interest rate that corresponds with the expected term. Expected dividend yield – The Company utilizes a dividend yield of zero, as it does not currently issue dividends and does not expect to in the future. The following assumptions were used to calculate the fair value of employee and non-employee stock option grants made during the following periods: Years Ended December 31, 2021 2020 Expected volatility 53.7% - 54.5% 48.8% -53.4% Expected term (years) 6.3 6.0 Risk-free interest rate 1.1% 0.6% Expected dividend yield — — Fair value of common stock per share $4.92 - $6.83 $3.89 - $4.23 Stock-Based Compensation The Company recorded stock-based compensation expense in the consolidated statements of operations as follows (in thousands): Years Ended December 31, 2021 2020 Cost of revenue $ 1,466 $ 905 Research and development 20,690 10,235 Sales and marketing 6,388 3,403 General and administrative 18,970 8,065 Total $ 47,514 $ 22,608 As of December 31, 2021, there was $123.2 million of unrecognized stock-based compensation expense, which is expected to be recognized over a weighted average period of 2.4 years.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders As a result of the Reverse Recapitalization, the Company has retroactively adjusted the weighted average number of shares of common stock outstanding prior to the Closing by multiplying them by the Exchange Ratio of 3.1057 used to determine the number of shares of common stock into which they converted. The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except per share data): Years Ended December 31, 2021 2020 Class A Class B Common Net loss attributable to common stockholders $ (8,032) $ (87,293) $ (75,234) Weighted average shares used in computing net loss per share attributable to Class A and Class B common stockholders, basic and diluted 12,330 134,007 90,190 Net loss per share attributable to Class A and Class B common stockholders, basic and diluted $ (0.65) $ (0.65) $ (0.83) The following potentially dilutive securities outstanding have been excluded from the computations of diluted net loss per share because such securities have an anti-dilutive impact due to losses reported (in thousands): As of December 31, 2021 2020 Redeemable convertible preferred stock — 190,477 Outstanding stock options 58,278 46,973 Unvested RSUs 2,511 — Unvested early exercised stock options subject to repurchase 422 693 Unvested restricted stock 3,210 7,062 Contingently issuable shares 181 204 Total 64,602 245,409

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit PlanThe Company has a 401(k) plan (“the Plan”) covering all eligible employees in the United States. The Company is allowed to make discretionary profit sharing and qualified non-elective contributions as defined by the Plan and as approved by the Board of Directors. Through December 31, 2020, the Company did not match eligible participants’ 401(k) contributions. As of January 1, 2021, the Company began matching a portion of eligible participants’ 401(k) contributions. The Company’s match totaled $1.1 million for the year ended December 31, 2021. No discretionary profit-sharing contributions have been made to date.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Loss before income taxes during the years ended December 31, 2021 and 2020 were as follows (in thousands): Years Ended December 31, 2021 2020 Domestic $ (94,693) $ (74,882) Foreign (475) (225) Loss before income taxes $ (95,168) $ (75,107) The provision for income taxes was as follows (in thousands): Years Ended December 31, 2021 2020 Current: Federal $ — $ — State 146 11 Foreign 11 116 Total current provision for income taxes 157 127 Deferred: Federal — — State — — Foreign — — Total deferred provision for income taxes — — Total provision for income taxes $ 157 $ 127 Income tax expense (benefit) differed from the amount computed by applying the federal statutory income tax rate of 21% to pretax loss as a result of the following: Years Ended December 31, 2021 2020 Statutory rate (21.0) % (21.0) % State tax 0.2 (2.5) Permanent items 0.7 0.4 Transaction costs (4.8) — Stock-based compensation 6.6 4.3 R&D credit (4.2) (4.2) Other — 0.1 Changes in valuation allowance 22.8 22.9 Foreign rate differential (0.1) 0.2 Effective tax rate 0.2 % 0.2 % The tax effects of significant items comprising the Company’s deferred taxes were as follows (in thousands): As of December 31, 2021 2020 Deferred tax assets: Net operating loss $ 96,423 $ 82,031 Credit carryforwards 14,162 10,143 Stock-based compensation 5,924 3,149 Lease liability 16,691 9,288 Reserves, accruals and other 1,774 1,152 Other 331 — Total deferred tax assets 135,305 105,763 Valuation allowance (120,873) (96,044) Total deferred tax assets, net 14,432 9,719 Deferred tax liabilities: Fixed asset basis and other — (858) ROU asset basis (14,432) (8,861) Total deferred tax liabilities (14,432) (9,719) Net deferred tax assets $ — $ — Based upon available objective evidence, management believes it is more likely than not that the U.S. net deferred tax assets will not be fully realizable. Accordingly, the Company has established a full valuation allowance for its U.S. net deferred tax assets. The valuation allowance increased by $24.8 million and $8.7 million, respectively, during 2021 and 2020. The Company had aggregate deferred tax assets of $135.3 million and $105.8 million as of December 31, 2021 and 2020, respectively. As of December 31, 2021, the Company had federal net operating loss carryforwards of $390.0 million, which begin to expire i n 2028, and state net operating loss carryforwards of $226.0 million, which begin to expire in 2028. Of the $390.0 million U.S. federal net operating losses $214.1 million is carried forward indefinitely but is limited to 80% of current year taxable income. As of December 31, 2021, the Company had federal tax credits of $16.6 million, which begin to expire in 2028, a nd state tax credits of $14.2 million, which do not expire. The Internal Revenue Code (“IRC”) limits the amount of net operating loss carryforwards that a company may use in a given year in the event of certain cumulative changes in ownership over a three-year period as described in Section 382 of the IRC. Utilization of net operating loss carryforwards and credits may be subject to a substantial annual limitation due to the ownership change limitations provided by the IRC, as amended, and similar state provisions. The annual limitation may result in the expiration of net operating losses and credits before utilization. The Company accounts for uncertainty in income taxes in accordance with ASC 740 Income Taxes . Tax positions are evaluated in a two-step process, whereby the Company first determines whether it is more likely than not that a tax position will be sustained upon examination by the tax authority, including resolutions of any related appeals or litigation processes, based on technical merit. If a tax position meets the more-likely-than-not recognition threshold it is then measured to determine the amount of benefit to recognize in the financial statements. The tax position is measured as the largest amount of benefit that is greater than 50% likely of being realized upon ultimate settlement. A reconciliation of the beginning and ending balances of unrecognized tax benefit were as follows (in thousands): Years Ended December 31, 2021 2020 Gross unrecognized tax benefits - beginning of year $ 10,143 $ 6,971 Increases related to current year tax positions 3,759 3,129 Increases related to prior year tax positions — 43 Gross unrecognized tax benefits - end of year $ 13,902 $ 10,143 All of the unrecognized tax benefits as of December 31, 2021 are accounted for as a reduction in the Company’s deferred tax assets. Due to the Company’s valuation allowance, none of the $13.9 million of unrecognized tax benefits, related solely to its federal and state research and development income tax credits, would affect the Company’s effective tax rate, if recognized. The Company does not believe it is reasonably possible that its unrecognized tax benefits will significantly change in the next twelve months. The Company recognizes interest and penalties related to unrecognized tax benefits as income tax expense. There were no interest or penalties accrued related to unrecognized tax benefits for the years ended December 31, 2021 and 2020, and no liability for accrued interest or penalties related to unrecognized tax benefits as of December 31, 2021 and 2020.

Geographical Information

Geographical Information	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Geographical Information	Geographical Information Revenue disaggregated by geography based on the customers’ location was as follows (in thousands): Years Ended December 31, 2021 2020 United States $ 183,724 $ 119,118 International 8,473 4,166 Total $ 192,197 $ 123,284 Substantially all of the Company’s long-lived assets are located in the United States.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company’s fiscal year ends on December 31. The Merger was accounted for as a reverse recapitalization in accordance with GAAP. This determination was primarily based on the evaluation of the following facts and circumstances: • Legacy Nextdoor stockholders had a relative majority of the voting power of Nextdoor; • The Board of Directors of Nextdoor had ten members, and Legacy Nextdoor stockholders had the ability to nominate a majority of the members of the Board of Directors; • Legacy Nextdoor’s senior management comprised the senior management roles of Nextdoor and were responsible for the day-to-day operations; • Nextdoor assumed the Nextdoor Holdings, Inc. name and Legacy Nextdoor’s corporate headquarters; and • The intended strategy and operations of Nextdoor continued Legacy Nextdoor’s strategy and operations to leverage technology to connect millions of neighbors online and in real life to build stronger, more vibrant, and resilient neighborhoods. Under this method of accounting, KVSB was treated as the “acquired” company for financial reporting purposes. Accordingly, the financial statements of Nextdoor represent the continuation of the financial statements of Legacy Nextdoor, with the Merger reflected as the equivalent of Nextdoor issuing common stock for the net assets of KVSB, accompanied by a recapitalization. The shares and corresponding capital amounts and all per share data related to Legacy Nextdoor’s outstanding redeemable convertible preferred stock, common stock, and stock-based awards prior to the Reverse Recapitalization have been retroactively adjusted using the Exchange Ratio (as defined in Note 3). The conversion of the outstanding shares of Legacy Nextdoor redeemable convertible preferred stock into shares of Class B common stock in connection with the Reverse Recapitalization and the issuance of Class A common stock are presented as of the Closing of the Merger in the consolidated statements of redeemable convertible preferred stock and stockholders’ equity (deficit). The net assets of KVSB were recognized as of the Closing at historical cost, with no goodwill or other intangible assets recorded. Operations prior to the Merger are those of Legacy Nextdoor and Legacy Nextdoor’s operations are the only ongoing operations of Nextdoor.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Estimates include, but are not limited to, valuation of financial instruments, valuation of common stock through the date of the Reverse Recapitalization, valuation of stock-based awards, revenue recognition, collectability of accounts receivable, valuation of acquired intangible assets and goodwill, useful lives of intangible assets, useful lives of property and equipment, the incremental borrowing rate applied in lease accounting, income taxes and deferred income tax assets and associated valuation allowances. The Company bases these estimates and assumptions on historical experience and various other assumptions that it considers reasonable. The actual results could differ materially from these estimates.
Foreign Currency	Foreign Currency The functional currency of the Company’s international subsidiaries is generally their local currency. The financial statements of these subsidiaries are translated into U.S. dollars using month-end exchange rates for assets and liabilities, historical exchange rates for equity, and average exchange rates for revenue and expenses. Translation gains and losses are recorded in accumulated other comprehensive income (loss) as a component of stockholders’ equity (deficit). Unrealized foreign exchange gains and losses due to the re-measurement of monetary assets and liabilities denominated in non-functional currencies and realized foreign exchange gains and losses on foreign exchange transactions are recorded in other income (expense), net in the consolidated statements of operations.
Cash and Cash Equivalents	Cash and Cash EquivalentsCash and cash equivalents consist of highly liquid investments with insignificant interest rate risk and original maturities of three months or less at the time of purchase. Cash and cash equivalents include demand deposits and money market accounts. Interest is accrued as earned. Cash and cash equivalents are recorded at cost, which approximates fair value.
Marketable Securities	Marketable Securities The Company’s marketable securities are comprised of commercial paper, corporate securities, U.S. Treasury securities, and asset-backed securities. The Company determines the appropriate classification of its investments at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its investments as available-for-sale securities as the Company may sell these securities at any time for use in its current operations or for other purposes, even prior to maturity. As a result, the Company classifies its investments, including securities with stated maturities beyond 12 months, within current assets on the consolidated balance sheets.
Fair Value Measurements	Fair Value Measurements The Company accounts for certain assets and liabilities at fair value, which is the expected exchange price that would be received for an asset or an exit price paid to transfer a liability in an orderly transaction between market participants on the measurement date. Assets and liabilities measured at fair value are classified into the following categories based on the degree to which the inputs the Company uses to measure the fair values are observable in active markets. The Company uses the most observable inputs available when measuring fair value. • Level 1: Observable inputs such as unadjusted quoted prices for identical assets or liabilities in active markets; • Level 2: Observable inputs such as quoted prices for similar assets or liabilities in active markets, quoted prices for identical assets or liabilities in inactive markets, or inputs that are derived principally from or corroborated by observable market data or other means; and • Level 3: Unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts The Company records accounts receivable at the original invoiced amount. The Company maintains an allowance for doubtful accounts for any receivables it may be unable to collect and reduces the allowance when it determines that it will be unable to collect specific receivables. The Company determines the allowance based on its receivables’ age, the customers’ credit quality, and current economic conditions, among other factors that may affect the customers’ ability to pay.
Restricted Cash	Restricted Cash The Company’s restricted cash balance is primarily invested in a savings account and pledged as collateral for standby letters of credit as security deposits for the Company’s office leases.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost, less accumulated depreciation and amortization. Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets as follows: Estimated Useful Life Computer equipment and software 3 years Furniture and fixtures 5 years Leasehold improvements Shorter of the estimated useful life of 5 years or the lease term Maintenance and repair costs are expensed as incurred.
Capitalized Internal-use Software	Capitalized Internal-use SoftwareThe Company capitalizes internal-use software costs when preliminary development efforts are successfully completed, management has authorized and committed project funding, and it is probable that the project will be completed, and the software will be used as intended. Costs related to preliminary project activities and post-implementation activities are expensed as incurred and costs related to the application development stage are capitalized. Capitalized costs are recorded as part of property and equipment, net. The capitalized costs related to internal-use software are amortized on a straight-line basis over an estimated useful life of two
Business Combinations	Business CombinationsThe Company includes the results of operations of the businesses that it acquires from the date of acquisition. The Company accounts for its acquisitions using the acquisition method of accounting. The Company allocates the fair value of purchase consideration to the tangible assets acquired, liabilities assumed, and intangible assets acquired, based on their estimated fair values. The excess of the fair value of purchase consideration over the values of these identifiable assets and liabilities is recorded as goodwill. When determining the fair value of assets acquired and liabilities assumed, management makes significant estimates and assumptions, especially with respect to intangible assets. Significant estimates in valuing certain identifiable assets include, but are not limited to, expected long-term market growth, future expected operating expenses, appropriate discount rates, and useful lives. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. Acquisition costs, such as legal and consulting fees, are expensed as incurred. During the measurement period, the Company may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon the conclusion of the measurement period, which is not to exceed one year from the acquisition date, any subsequent adjustments are recorded in the consolidated statements of operations.
Goodwill and Other Acquired Intangible Assets	Goodwill and Other Acquired Intangible Assets Goodwill represents the excess of the purchase price over the fair value of net assets acquired in connection with business combinations accounted for using the acquisition method of accounting. Goodwill is not amortized, but is tested for impairment at least annually, in the fourth quarter, or whenever events or changes in circumstances indicate that goodwill might be impaired. For all periods presented the Company had one reporting unit. The Company’s test for goodwill impairment starts with a qualitative assessment to determine whether it is necessary to perform the quantitative goodwill impairment test. If the Company determines, based on the qualitative factors, that the fair value of the reporting unit is more likely than not to be less than the carrying amount, then a quantitative goodwill impairment test is required. There was no impairment of goodwill recorded for the years ended December 31, 2021 and 2020. Intangible assets consist of identifiable intangible assets, including customer relationships and developed technology, resulting from the Company’s acquisitions. Acquired intangible assets are recorded at cost, net of accumulated amortization. Intangible assets are amortized on a straight-line basis over their estimated useful lives. Amortization costs are recorded in sales and marketing in the consolidated statements of operations.
Impairment of Long-Lived Assets	Impairment of Long-Lived AssetsProperty and equipment and other long-lived assets, such as finite-lived intangible assets, subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If impairment is indicated, an impairment loss is recognized as the amount by which the carrying amount exceeds the fair value.
Leases	Leases Results and disclosure requirements for all periods presented are presented under ASU 2016-02, Leases (“Topic 842”). The Company has various lease agreements related to real estate that are all classified as operating leases. At the inception of the Company’s contracts it determines if the contract is or contains a lease. A contract is or contains a lease if it conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The Company has elected not to separate the lease and non-lease components within the contract. For leases that have greater than a 12-month lease term, right-of-use (“ROU”) assets and operating lease liabilities are recognized on the consolidated balance sheets at commencement date based on the present value of remaining fixed lease payments. Certain of the Company’s leases include options to extend the lease, with renewal terms that can extend the lease term from one month to five years. If the Company is reasonably certain to exercise an option to extend a lease, the extension period is included as part of the ROU asset and the operating lease liability. When the discount rate implicit in the lease cannot be readily determined, the Company uses its incremental borrowing rate at lease commencement in order to discount lease payments to present value for purposes of performing lease classification tests and measuring the lease liability. The Company’s incremental borrowing rate represents the rate of interest the Company would have to pay to borrow, on a collateralized basis, over a similar term an amount equal to the lease payments in a similar economic environment. The operating lease ROU asset also includes accrued lease expense resulting from the straight-line accounting under prior accounting methods, which is now being amortized over the remaining life of the lease. The Company’s lease payments are largely fixed. Variable lease payments exist in circumstances such as payments for property tax, insurance, and common area maintenance. Variable lease payments are recognized in operating expense in the period in which the obligation for those payments are incurred. Certain of the Company’s leases include an option to early terminate the lease. The Company’s leases may contain early termination options which may result in an early termination fee. The Company early terminated one of its leases in October 2020 and incurred an early termination fee of $0.1 million. The Company has a significant lease for its new headquarters in San Francisco, California, which does not include an option to early terminate. The first portion of the lease commenced in June 2020 and the second, and final portion of the lease, commenced in January 2021. For the Company’s leases, it has elected to not apply the recognition requirements to leases of twelve months or less. These leases are expensed on a straight-line basis and no operating lease liability will be recorded.
Concentration of Credit and Customer Risk	Concentration of Credit and Customer Risks Financial instruments that are exposed to concentrations of credit risk consist principally of cash and cash equivalents, marketable securities and accounts receivable. The Company maintains cash and cash equivalents and marketable securities with domestic and foreign financial institutions and at times may exceed federally insured limits. The Company performs periodic evaluations of the relative credit standing of these institutions. The Company maintains investments in U.S. government debt and agency securities, corporate debt securities, and commercial paper that carry high credit ratings and accordingly, minimal credit risk exists with respect to these balances.
Revenue Recognition, Deferred Revenue, Practical Expedients and Exemptions, and Cost of Revenue	Revenue Recognition The Company generates a majority of its revenue from the delivery of advertising services. The Company determines revenue recognition through the following steps: (1) Identification of the contract, or contracts, with a customer (2) Identification of the performance obligations in the contract (3) Determination of the transaction price (4) Allocation of the transaction price to the performance obligations in the contract (5) Recognition of revenue when, or as, the Company satisfies a performance obligation The Company recognizes advertising revenue after satisfying its contractual performance obligation, which, for the majority of its advertising arrangements, is when an advertising impression is displayed to users. None of the Company’s arrangements contain minimum impression guarantees. The Company typically bills advertisers on a monthly basis and the payment terms vary by customer type and location. The Company has other advertising arrangements for the sale of neighborhood sponsorship and local deals which are typically fixed-fee arrangements and revenue is recognized on a straight-line basis over the non-cancellable contractual term of the agreement, generally beginning on the date its service is made available to the customer. Deferred Revenue In certain advertising arrangements the Company requires payment upfront from its customers. The Company records deferred revenue when it collects cash from customers in advance of revenue recognition. As of December 31, 2021 and 2020, deferred revenue was $3.4 million and $2.6 million, respectively, and included within accrued expenses and other current liabilities on the consolidated balance sheets. For the years ended December 31, 2021 and 2020, revenue recognized from deferred revenue at the beginning of each year was $2.5 million and $0.7 million, respectively. Practical Expedients and Exemptions The Company expenses sales commissions as incurred because the expected period of benefit is less than one year. These costs are recorded within sales and marketing expenses in the consolidated statements of operations. The Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which it recognizes revenue at the amount to which it has the right to invoice for services performed. Cost of Revenue Cost of revenue consists primarily of expenses associated with the delivery of the Company’s revenue generating activities, including third-party costs of hosting its platform and allocated personnel-related costs, including salaries, benefits and stock-based compensation for employees engaged in development of its revenue generating products. Cost of revenue also includes third-party costs associated with delivering and supporting its advertising products and credit card transaction fees related to processing customer transactions.
Research and Development	Research and Development Research and development expenses consist primarily of personnel-related costs, including salaries, benefits and stock-based compensation for its employees engaged in research and development, as well as costs for consultants, contractors and third-party software. In addition, allocated overhead costs, such as facilities, information technology, and depreciation are included in research and development expenses.
Sales and Marketing, and General and Administrative	Sales and Marketing Sales and marketing expenses consist primarily of personnel-related costs and other costs which include salaries, commissions, benefits, and stock-based compensation for employees engaged in sales and marketing activities as well as other costs including third-party consulting, public relations, allocated overhead costs, and amortization of acquired intangible assets. Sales and marketing expenses also include brand and performance marketing for both user and small and mid-sized customer acquisition, and neighbor services, which includes personnel-related costs for the Company's neighbor support team, its outsourced neighbor support function, and verification costs. General and Administrative General and administrative expenses consist primarily of personnel-related costs, including salaries, benefits, and stock-based compensation, for certain executives, finance, legal, information technology, human resources, and other administrative employees. In addition, general and administrative expenses include fees and costs for professional services, including consulting, third-party legal and accounting services, and allocated overhead costs.
Advertising Costs	Advertising CostsAdvertising costs which consist primarily of brand and performance marketing are expensed as incurred and are included in sales and marketing expense in the consolidated statements of operations.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred income taxes are recognized for differences between financial reporting and tax bases of assets and liabilities at the enacted statutory tax rates in effect for the years in which the temporary differences are expected to reverse. Management makes an assessment of the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s historical operating performance and the recorded cumulative net losses in prior fiscal periods, the U.S. net deferred tax assets have been fully offset by a valuation allowance. The Company operates in various tax jurisdictions which are subject to audit by various tax authorities. The Company recognizes a tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the financial statements from such positions are then measured based on the largest benefit that has a greater than 50% cumulative likelihood of being realized upon settlement. The Company recognizes interest and penalties related to unrecognized tax benefits in the income tax provision in the consolidated statements of operations.
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders The Company presents net loss per share attributable to common stockholders in conformity with the two-class method required for multiple classes of common stock and participating securities. Under the two-class method, net loss is attributed to common stockholders and participating securities based on their participation rights. The rights, including the liquidation and dividend rights, of the Class A common stock and Class B common stock are substantially identical, other than voting rights. Accordingly, the Class A common stock and Class B common stock share proportionately in the Company’s net losses. The Company considers its redeemable convertible preferred stock (prior to the Reverse Recapitalization), early exercised stock options, and unvested restricted stock to be participating securities and contractually entitles the holders of such shares to participate in dividends but does not contractually obligate the holders of such shares to participate in the Company’s losses. As such, net losses for the periods presented were not allocated to these securities. The Company computes basic net loss per share attributable to common stockholders by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, adjusted for outstanding shares that are subject to repurchase. Diluted net loss per share attributable to common stockholders is computed by giving effect to all potentially dilutive securities outstanding for the period. For periods in which the Company reports net losses, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, because all potentially dilutive securities are anti-dilutive.
Stock-Based Compensation	Stock-Based CompensationStock-based compensation expense for stock-based awards granted to employees and non-employees is measured based on the grant date fair value of the awards and recognized in the consolidated statements of operations on a straight-line basis over the period during which services are provided in exchange for the award, generally, the vesting period of the award. The grant date fair value of stock options granted is estimated using the Black-Scholes option pricing model. Forfeitures are accounted for as they occur.
Segments	SegmentsThe Company has one reportable and operating segment. The Company’s chief operating decision maker is its Chief Executive Officer (“CEO”), who reviews financial information presented on a consolidated basis for purposes of making operating decisions, assessing financial performance, and allocating resources.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement . ASU 2018-13 changes the disclosure requirements for fair value measurement. The Company adopted this standard as of January 1, 2020, and the adoption did not have a material impact on the Company’s consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses ( Topic 326 ): Measurement of Credit Losses on Financial Instruments , and has since issued various amendments including ASU 2018-19, ASU 2019-04, and ASU 2019-05. The guidance and related amendments modify the accounting for credit losses for most financial assets and require the use of an expected loss model, replacing the currently used incurred loss method. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The new guidance will be effective for the Company beginning January 1, 2023, though early adoption is permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures. In December 2019, the FASB issued ASU 2019-12, Income Taxes – Topic 740 – Simplifying the Accounting for Income Taxes , which simplifies the accounting for income taxes by removing certain exceptions to the general principals in Topic 740. The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. The ASU is effective for fiscal years beginning after December 15, 2021, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Schedule of Property and Equipment, Net	Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets as follows: Estimated Useful Life Computer equipment and software 3 years Furniture and fixtures 5 years Leasehold improvements Shorter of the estimated useful life of 5 years or the lease term Property and equipment, net consisted of the following (in thousands): As of December 31, 2021 2020 Computer equipment and software $ 3,123 $ 2,002 Furniture and fixtures 2,201 1,174 Capitalized internal-use software 1,842 1,842 Leasehold improvements 9,502 2,850 Property and equipment, gross 16,668 7,868 Less: accumulated depreciation and amortization (4,123) (2,150) Property and equipment, net $ 12,545 $ 5,718

Reverse Recapitalization (Table

Reverse Recapitalization (Tables)	12 Months Ended
	Dec. 31, 2021
Reverse Recapitalization [Abstract]
Schedule of Reverse Recapitalization	The following table presents the number of shares of common stock issued and outstanding immediately following the Reverse Recapitalization: Shares KVSB Class A common stock, outstanding prior to Reverse Recapitalization 42,767,100 Less: redemption of KVSB Class A common stock (1,222,040) Conversion of KVSB Class B founder shares 7,347,249 Conversion of KVSB Class K common stock 3,061,354 Shares issued to PIPE Investors 27,000,000 Nextdoor Class A common stock 78,953,663 Conversion of Legacy Nextdoor common stock (1) 113,526,555 Conversion of Legacy Nextdoor redeemable convertible preferred stock (2) 190,477,421 Nextdoor Class B common stock 304,003,976 Total shares of common stock immediately after Reverse Recapitalization 382,957,639 (1) Upon the completion of the Reverse Recapitalization, the 36,554,506 outstanding shares of Legacy Nextdoor common stock were converted into shares of Nextdoor Class B common stock using the Exchange Ratio. (2) Upon the completion of the Reverse Recapitalization, all 61,331,815 outstanding shares of Legacy Nextdoor redeemable convertible preferred stock converted into Legacy Nextdoor common stock on a one-to-one basis, which were then converted into shares of Nextdoor Class B common stock using the Exchange Ratio. Year Ended December 31, 2021 Funds held in KVSB's trust account $ 416,359 Funds held in KVSB's operating cash account 194 Proceeds from the PIPE Investment 270,000 Less: amount paid to redeem public shares of KVSB's Class A common stock (12,221) Less: transaction costs incurred by KVSB (45,843) Proceeds from the Reverse Recapitalization 628,489 Less: non-cash liabilities assumed from KVSB (203) Less: unpaid deferred transaction costs (314) Less: payment of transaction costs related to the Reverse Recapitalization (5,384) Net cash from issuance of common stock upon the Reverse Recapitalization, net of issuance costs $ 622,588

Cash Equivalents and Marketab_2

Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Schedule of Cash and Cash Equivalents	The amortized costs, unrealized gains and losses, and estimated fair values of the Company’s cash equivalents and marketable securities were as follows (in thousands): As of December 31, 2021 Amortized Unrealized Unrealized Estimated Cash equivalents: Money market funds $ 474,294 $ — $ — $ 474,294 Marketable securities: Commercial paper 83,728 — — 83,728 Corporate securities 78,353 24 (14) 78,363 U.S. Treasury securities 15,200 — (12) 15,188 Asset-backed securities 16,735 — (15) 16,720 Total marketable securities 194,016 24 (41) 193,999 Total $ 668,310 $ 24 $ (41) $ 668,293 As of December 31, 2020 Amortized Unrealized Unrealized Estimated Cash equivalents: Money market funds $ 28,371 $ — $ — $ 28,371 Marketable securities: Commercial paper 27,473 — — 27,473 Corporate securities 6,940 — (2) 6,938 U.S. Treasury securities 16,157 1 — 16,158 Asset-backed securities 2,772 — — 2,772 Total marketable securities 53,342 1 (2) 53,341 Total $ 81,713 $ 1 $ (2) $ 81,712
Schedule of Marketable Securities	The amortized costs, unrealized gains and losses, and estimated fair values of the Company’s cash equivalents and marketable securities were as follows (in thousands): As of December 31, 2021 Amortized Unrealized Unrealized Estimated Cash equivalents: Money market funds $ 474,294 $ — $ — $ 474,294 Marketable securities: Commercial paper 83,728 — — 83,728 Corporate securities 78,353 24 (14) 78,363 U.S. Treasury securities 15,200 — (12) 15,188 Asset-backed securities 16,735 — (15) 16,720 Total marketable securities 194,016 24 (41) 193,999 Total $ 668,310 $ 24 $ (41) $ 668,293 As of December 31, 2020 Amortized Unrealized Unrealized Estimated Cash equivalents: Money market funds $ 28,371 $ — $ — $ 28,371 Marketable securities: Commercial paper 27,473 — — 27,473 Corporate securities 6,940 — (2) 6,938 U.S. Treasury securities 16,157 1 — 16,158 Asset-backed securities 2,772 — — 2,772 Total marketable securities 53,342 1 (2) 53,341 Total $ 81,713 $ 1 $ (2) $ 81,712
Schedule of Investments Classified by Contractual Maturity Date	The following tables present the contractual maturities of the Company’s marketable securities (in thousands): As of December 31, 2021 Amortized Cost Estimated Fair Value Due within one year $ 137,077 $ 137,043 Due after one to four years 56,939 56,956 Total $ 194,016 $ 193,999 As of December 31, 2020 Amortized Cost Estimated Fair Value Due within one year $ 53,342 $ 53,341

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Fair Value on Recurring Basis	The following table presents information about the Company’s financial assets that are measured at fair value on a recurring basis (in thousands): Fair Value Measurement as of December 31, 2021 Level 1 Level 2 Total Assets: Cash equivalents: Money market funds $ 474,294 $ — $ 474,294 Marketable securities: Commercial paper — 83,728 83,728 Corporate securities — 78,363 78,363 U.S. Treasury securities — 15,188 15,188 Asset-backed securities — 16,720 16,720 Total marketable securities — 193,999 193,999 Total cash equivalents and marketable securities $ 474,294 $ 193,999 $ 668,293 Fair Value Measurement as of December 31, 2020 Level 1 Level 2 Total Assets: Cash equivalents: Money market funds $ 28,371 $ — $ 28,371 Marketable securities: Commercial paper — 27,473 27,473 Corporate securities — 6,938 6,938 U.S. Treasury securities — 16,158 16,158 Asset-backed securities — 2,772 2,772 Total marketable securities — 53,341 53,341 Total cash equivalents and marketable securities $ 28,371 $ 53,341 $ 81,712

Other Balance Sheet Components

Other Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property and Equipment, Net	Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets as follows: Estimated Useful Life Computer equipment and software 3 years Furniture and fixtures 5 years Leasehold improvements Shorter of the estimated useful life of 5 years or the lease term Property and equipment, net consisted of the following (in thousands): As of December 31, 2021 2020 Computer equipment and software $ 3,123 $ 2,002 Furniture and fixtures 2,201 1,174 Capitalized internal-use software 1,842 1,842 Leasehold improvements 9,502 2,850 Property and equipment, gross 16,668 7,868 Less: accumulated depreciation and amortization (4,123) (2,150) Property and equipment, net $ 12,545 $ 5,718
Schedule of Intangible Assets, Net	Intangible assets, net consisted of the following (in thousands): As of December 31, 2021 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Remaining Life (years) Customer relationships $ 7,068 $ (4,684) $ 2,384 3.0 Developed technology 4,600 (2,149) 2,451 2.7 Total intangible assets, net $ 11,668 $ (6,833) $ 4,835 2.8 As of December 31, 2020 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Weighted Average Remaining Life (years) Customer relationships $ 7,068 $ (3,451) $ 3,617 3.0 Developed technology 4,600 (1,230) 3,370 3.7 Total intangible assets, net $ 11,668 $ (4,681) $ 6,987 3.3
Schedule of Expected Future Amortization Expense for Intangible Assets	Expected future amortization expense for intangible assets as of December 31, 2021 was as follows (in thousands): Years Ending December 31, Amount 2022 $ 1,773 2023 1,773 2024 1,054 2025 235 Thereafter — Total $ 4,835
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): As of December 31, 2021 2020 Accrued compensation $ 3,375 $ 6,888 Liability for early exercise of unvested stock options 690 1,133 Taxes payable 879 516 Deferred revenue 3,388 2,585 Other accrued and current liabilities 7,112 3,876 Accrued expenses and other current liabilities $ 15,444 $ 14,998

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Schedule of Components of Lease Costs, Other Information, and Lease Terms and Discount Rates	The components of lease costs were as follows (in thousands): Years Ended December 31, 2021 2020 Operating lease cost $ 9,864 $ 6,278 Short-term lease cost 525 495 Variable lease cost 409 452 Total $ 10,798 $ 7,225 Other information related to the Company’s operating leases was as follows (in thousands): Years Ended December 31, 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 6,585 $ 5,624 ROU assets obtained in exchange for lease obligations: Operating leases $ 28,252 $ 39,664 Lease terms and discount rates for operating leases were as follows: As of December 31, 2021 2020 Weighted average remaining lease term (years) 7.3 8.2 Weighted average discount rate 4.5 % 5.3 %
Schedule of Future Minimum Lease Payments under Operating Leases	As of December 31, 2021, future minimum lease payments under operating leases were as follows (in thousands): Years Ending December 31, Amount 2022 $ 10,045 2023 10,347 2024 10,657 2025 10,977 2026 11,306 Thereafter 27,697 Total lease payments 81,029 Less: imputed interest (12,300) Present value of lease liabilities 68,729 Less: current operating lease liabilities (7,131) Long-term operating lease liabilities $ 61,598

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Purchase Commitments	As of December 31, 2021, the Company had non-cancellable purchase commitments with certain service providers primarily related to the provision of cloud computing services as follows (in thousands): Total Commitments Years Ending December 31, 2022 $ 18,978 2023 22,528 2024 10,417 Thereafter — Total $ 51,923

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Schedule of Common Stock Reserved for Future Issuance	Shares of common stock reserved for future issuance on an as-converted basis were as follows (in thousands): As of December 31, 2021 2020 Redeemable convertible preferred stock — 190,477 Stock options outstanding 58,278 46,973 Unvested restricted stock units (RSUs) 2,511 — Shares reserved for future award issuances 77,924 12,558 Total 138,713 250,008
Summary of Stock Option Activity	A summary of the Company’s stock option activity for the year ended December 31, 2021 and related information is as follows (in thousands, except per share data): Number of Options Weighted- Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Balances at December 31, 2020 46,973 $ 1.80 7.8 $ 28,467 Options granted 25,262 $ 3.05 Options exercised (10,325) $ 1.48 Options forfeited or expired (3,632) $ 2.50 Balances at December 31, 2021 58,278 $ 2.35 8.1 $ 322,799 Options vested and exercisable at December 31, 2021 23,443 $ 1.72 6.6 $ 144,608
Schedule of Restricted Stock Unit Activity	A summary of the Company’s RSU activity for the year ended December 31, 2021 and related information is as follows (in thousands, except per share data): Number of Shares Weighted Average Grant Date Fair Value Unvested at December 31, 2020 — $ — RSUs granted 2,701 $ 8.74 RSUs vested (166) $ 8.91 RSUs forfeited (24) $ 7.68 Unvested at December 31, 2021 2,511 $ 8.74
Schedule of Assumptions Used to Calculate Fair Value of Stock Option Grants	The following assumptions were used to calculate the fair value of employee and non-employee stock option grants made during the following periods: Years Ended December 31, 2021 2020 Expected volatility 53.7% - 54.5% 48.8% -53.4% Expected term (years) 6.3 6.0 Risk-free interest rate 1.1% 0.6% Expected dividend yield — — Fair value of common stock per share $4.92 - $6.83 $3.89 - $4.23
Schedule of Stock-based Compensation Expense	The Company recorded stock-based compensation expense in the consolidated statements of operations as follows (in thousands): Years Ended December 31, 2021 2020 Cost of revenue $ 1,466 $ 905 Research and development 20,690 10,235 Sales and marketing 6,388 3,403 General and administrative 18,970 8,065 Total $ 47,514 $ 22,608

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Schedule of Earnings Per Share	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except per share data): Years Ended December 31, 2021 2020 Class A Class B Common Net loss attributable to common stockholders $ (8,032) $ (87,293) $ (75,234) Weighted average shares used in computing net loss per share attributable to Class A and Class B common stockholders, basic and diluted 12,330 134,007 90,190 Net loss per share attributable to Class A and Class B common stockholders, basic and diluted $ (0.65) $ (0.65) $ (0.83)
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following potentially dilutive securities outstanding have been excluded from the computations of diluted net loss per share because such securities have an anti-dilutive impact due to losses reported (in thousands): As of December 31, 2021 2020 Redeemable convertible preferred stock — 190,477 Outstanding stock options 58,278 46,973 Unvested RSUs 2,511 — Unvested early exercised stock options subject to repurchase 422 693 Unvested restricted stock 3,210 7,062 Contingently issuable shares 181 204 Total 64,602 245,409

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Loss before Income Taxes	Loss before income taxes during the years ended December 31, 2021 and 2020 were as follows (in thousands): Years Ended December 31, 2021 2020 Domestic $ (94,693) $ (74,882) Foreign (475) (225) Loss before income taxes $ (95,168) $ (75,107)
Schedule of Provision for Income Taxes	The provision for income taxes was as follows (in thousands): Years Ended December 31, 2021 2020 Current: Federal $ — $ — State 146 11 Foreign 11 116 Total current provision for income taxes 157 127 Deferred: Federal — — State — — Foreign — — Total deferred provision for income taxes — — Total provision for income taxes $ 157 $ 127
Schedule of Effective Tax Rate	Income tax expense (benefit) differed from the amount computed by applying the federal statutory income tax rate of 21% to pretax loss as a result of the following: Years Ended December 31, 2021 2020 Statutory rate (21.0) % (21.0) % State tax 0.2 (2.5) Permanent items 0.7 0.4 Transaction costs (4.8) — Stock-based compensation 6.6 4.3 R&D credit (4.2) (4.2) Other — 0.1 Changes in valuation allowance 22.8 22.9 Foreign rate differential (0.1) 0.2 Effective tax rate 0.2 % 0.2 %
Schedule of Deferred Taxes	The tax effects of significant items comprising the Company’s deferred taxes were as follows (in thousands): As of December 31, 2021 2020 Deferred tax assets: Net operating loss $ 96,423 $ 82,031 Credit carryforwards 14,162 10,143 Stock-based compensation 5,924 3,149 Lease liability 16,691 9,288 Reserves, accruals and other 1,774 1,152 Other 331 — Total deferred tax assets 135,305 105,763 Valuation allowance (120,873) (96,044) Total deferred tax assets, net 14,432 9,719 Deferred tax liabilities: Fixed asset basis and other — (858) ROU asset basis (14,432) (8,861) Total deferred tax liabilities (14,432) (9,719) Net deferred tax assets $ — $ —
Schedule of Unrecognized Tax Benefits	A reconciliation of the beginning and ending balances of unrecognized tax benefit were as follows (in thousands): Years Ended December 31, 2021 2020 Gross unrecognized tax benefits - beginning of year $ 10,143 $ 6,971 Increases related to current year tax positions 3,759 3,129 Increases related to prior year tax positions — 43 Gross unrecognized tax benefits - end of year $ 13,902 $ 10,143

Geographical Information (Table

Geographical Information (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Schedule of Revenue Disaggregated by Geography	Revenue disaggregated by geography based on the customers’ location was as follows (in thousands): Years Ended December 31, 2021 2020 United States $ 183,724 $ 119,118 International 8,473 4,166 Total $ 192,197 $ 123,284

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)	1 Months Ended	12 Months Ended
	Oct. 31, 2020USD ($)	Dec. 31, 2021USD ($)membersegmentreporting_unit	Dec. 31, 2020USD ($)
Concentration Risk [Line Items]
Number of members of Board of Directors | member		10
Restricted cash, current		$ 0	$ 1,101,000
Capitalized software costs		$ 0	200,000
Number of reporting units | reporting_unit		1
Goodwill impairment		$ 0	0
Long-lived asset impairment		0	0
Termination fee	$ 100,000
Deferred revenue		3,388,000	2,585,000
Revenue recognized from contract with customer		2,500,000	700,000
Advertising expense		$ 37,500,000	$ 23,700,000
Number of reportable segments | segment		1
Number of operating segments | segment		1
Minimum
Concentration Risk [Line Items]
Lessee, operating lease, renewal term		1 month
Maximum
Concentration Risk [Line Items]
Lessee, operating lease, renewal term		5 years
Capitalized internal-use software | Minimum
Concentration Risk [Line Items]
Property and equipment, useful life		2 years
Capitalized internal-use software | Maximum
Concentration Risk [Line Items]
Property and equipment, useful life		3 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Property, Plant and Equipment Useful Lives (Details)	12 Months Ended
	Dec. 31, 2021
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years

Reverse Recapitalization - Narr

Reverse Recapitalization - Narrative (Details) $ in Thousands	Nov. 05, 2021USD ($)shares	Jul. 06, 2021USD ($)shares	Dec. 31, 2021USD ($)voteshares	Dec. 31, 2020USD ($)shares		Dec. 31, 2019shares	[1]
Business Acquisition [Line Items]
Redeemable convertible preferred stock issued (in shares)			0	190,477,000
Redeemable convertible preferred stock outstanding (in shares)			0	190,477,000	[1]	190,477,000
Common stock outstanding (in shares)	382,957,639
Recapitalization exchange ratio			3.1057
Stock options outstanding (in shares)			58,278,000	46,973,000
Shares reserved for issuance (in shares)			138,713,000	250,008,000
Sale of stock, consideration received on transaction | $		$ 270,000
Proceeds from the Reverse Recapitalization | $	$ 628,500		$ 628,489	$ 0
Funds held in KVSB's trust account | $	416,400		416,359
Funds held in KVSB's operating cash account | $	200		194
Proceeds from private placement | $	270,000		270,000
Amount paid to redeem public shares | $	12,200		$ 12,221
Reverse recapitalization costs incurred | $	$ 5,700
Common Stock
Business Acquisition [Line Items]
Conversion ratio (in shares)	1
Legacy Nextdoor
Business Acquisition [Line Items]
Common stock outstanding (in shares)	97,886,321
Common stock issued (in shares)	97,886,321
Stock options outstanding (in shares)	19,196,313
Legacy Nextdoor | Common Stock
Business Acquisition [Line Items]
Convertible preferred stock converted (in shares)	61,331,815
Legacy Nextdoor | Pixel Labs, Inc
Business Acquisition [Line Items]
Contingent equity consideration (in shares)	58,135
Legacy Nextdoor | Unvested RSUs
Business Acquisition [Line Items]
Unvested restricted stock units (RSUs)	866,687
Redeemable convertible preferred stock
Business Acquisition [Line Items]
Conversion of stock (in shares)	190,477,421
Conversion ratio (in shares)	1
Redeemable convertible preferred stock | Legacy Nextdoor
Business Acquisition [Line Items]
Redeemable convertible preferred stock issued (in shares)	61,331,815
Redeemable convertible preferred stock outstanding (in shares)	61,331,815
Class B Common Stock
Business Acquisition [Line Items]
Common stock outstanding (in shares)	304,003,976		304,701,000	103,777,000
Common stock issued (in shares)	304,003,976		304,701,000	103,777,000
Recapitalization exchange ratio			3.1057
Stock options outstanding (in shares)	59,616,898
Number of votes per share | vote			10
Class B Common Stock | KVSB
Business Acquisition [Line Items]
Conversion of stock (in shares)	5,000,000
Stock issued in reverse recapitalization (in shares)	7,347,249
Class B Common Stock | Pixel Labs, Inc
Business Acquisition [Line Items]
Shares reserved for issuance (in shares)	180,549
Class B Common Stock | Unvested RSUs
Business Acquisition [Line Items]
Unvested restricted stock units (RSUs)	2,691,577
Class B Common Stock | Share-based payment arrangement
Business Acquisition [Line Items]
Shares reserved for issuance (in shares)	62,308,475
Class B Common Stock | Legacy Nextdoor
Business Acquisition [Line Items]
Common stock outstanding (in shares)	36,554,506
Class A Common Stock
Business Acquisition [Line Items]
Common stock outstanding (in shares)	78,953,663		78,954,000	0
Common stock issued (in shares)	78,953,663		78,954,000	0
Conversion of stock (in shares)	113,526,555
Sale of stock, number of shares issued in transaction (in shares)		27,000,000
Number of votes per share | vote			1
Class A Common Stock | KVSB
Business Acquisition [Line Items]
Conversion of stock (in shares)	40,412,372
Stock redeemed during period (in shares)	1,222,040
Sale of stock, number of shares issued in transaction (in shares)		750,000
Class A Common Stock | Legacy Nextdoor
Business Acquisition [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		4,500,000
Class A Common Stock | Private Placement | KVSB
Business Acquisition [Line Items]
Conversion of stock (in shares)	1,132,688
Class A Common Stock | Chief Executive Officer And President
Business Acquisition [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		500,000
Class A Common Stock | Conversion of KVSB Class B Common Stock
Business Acquisition [Line Items]
Stock issued in reverse recapitalization (in shares)	7,347,249
Class A Common Stock | Conversion of KVSB Class K Common Stock
Business Acquisition [Line Items]
Stock issued in reverse recapitalization (in shares)	3,061,354
Common Class K | KVSB
Business Acquisition [Line Items]
Conversion of stock (in shares)	5,000,000
Stock issued in reverse recapitalization (in shares)	3,061,354
[1]	The shares of the Company’s common and redeemable convertible preferred stock prior to the Reverse Recapitalization (as defined in Note 1) have been retroactively restated to reflect the exchange ratio of 3.1057 established in the Merger Agreement as described in Note 3.

Reverse Recapitalization - Comm

Reverse Recapitalization - Common Stock Issued and Outstanding Following the Reverse Recapitalization (Details) - shares	Nov. 05, 2021	Dec. 31, 2021	Dec. 31, 2020		Dec. 31, 2019	[1]
Business Acquisition [Line Items]
Common stock outstanding (in shares)	382,957,639
Shares issued (in shares)	27,000,000
Redeemable convertible preferred stock issued (in shares)		0	190,477,000
Redeemable convertible preferred stock outstanding (in shares)		0	190,477,000	[1]	190,477,000
Class B Common Stock
Business Acquisition [Line Items]
Common stock outstanding (in shares)	304,003,976	304,701,000	103,777,000
Class A Common Stock
Business Acquisition [Line Items]
Common stock outstanding (in shares)	78,953,663	78,954,000	0
Conversion of stock (in shares)	113,526,555
Redeemable convertible preferred stock
Business Acquisition [Line Items]
Conversion of stock (in shares)	190,477,421
Conversion ratio (in shares)	1
KVSB | Class B Common Stock
Business Acquisition [Line Items]
Conversion of shares	7,347,249
Conversion of stock (in shares)	5,000,000
KVSB | Common Class K
Business Acquisition [Line Items]
Conversion of shares	3,061,354
Conversion of stock (in shares)	5,000,000
KVSB | Class A Common Stock
Business Acquisition [Line Items]
Less: redemption of KVSB Class A common stock (in shares)	(1,222,040)
Conversion of stock (in shares)	40,412,372
KVSB
Business Acquisition [Line Items]
Common stock outstanding (in shares)	42,767,100
Less: redemption of KVSB Class A common stock (in shares)	(1,222,040)
Legacy Nextdoor
Business Acquisition [Line Items]
Common stock outstanding (in shares)	97,886,321
Legacy Nextdoor | Class B Common Stock
Business Acquisition [Line Items]
Common stock outstanding (in shares)	36,554,506
Legacy Nextdoor | Redeemable convertible preferred stock
Business Acquisition [Line Items]
Redeemable convertible preferred stock issued (in shares)	61,331,815
Redeemable convertible preferred stock outstanding (in shares)	61,331,815
[1]	The shares of the Company’s common and redeemable convertible preferred stock prior to the Reverse Recapitalization (as defined in Note 1) have been retroactively restated to reflect the exchange ratio of 3.1057 established in the Merger Agreement as described in Note 3.

Reverse Recapitalization - Elem

Reverse Recapitalization - Elements Reconciled the Reserve Recapitalization (Details) - USD ($) $ in Thousands	Nov. 05, 2021	Dec. 31, 2021	Dec. 31, 2020
Reverse Recapitalization [Abstract]
Funds held in KVSB's trust account	$ 416,400	$ 416,359
Funds held in KVSB's operating cash account	200	194
Proceeds from the PIPE Investment	270,000	270,000
Less: amount paid to redeem public shares of KVSB's Class A common stock	(12,200)	(12,221)
Less: transaction costs incurred by KVSB		(45,843)
Proceeds from the Reverse Recapitalization	$ 628,500	628,489	$ 0
Less: non-cash liabilities assumed from KVSB		(203)
Less: unpaid deferred transaction costs		(314)
Less: payment of transaction costs related to the Reverse Recapitalization		(5,384)
Net cash from issuance of common stock upon the Reverse Recapitalization, net of issuance costs		$ 622,588

Acquisitions - Narrative (Detai

Acquisitions - Narrative (Details) - Pixel Labs, Inc - USD ($) $ in Millions	Aug. 27, 2019	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Business combination, consideration transferred	$ 7.6
Issuance of common stock in connection with acquisition (in shares)		20,885	29,665
Time-Based Cash Holdback
Business Acquisition [Line Items]
Accrued purchase consideration for acquisition	0.7
Time-Based Share Holdback
Business Acquisition [Line Items]
Accrued purchase consideration for acquisition	$ 0.2

Cash Equivalents and Marketab_3

Cash Equivalents and Marketable Securities - Amortized Cost, Unrealized Gains and Losses, and Estimated Fair Values (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Marketable securities:
Amortized Cost	$ 194,016	$ 53,342
Unrealized Gain	24	1
Unrealized Loss	(41)	(2)
Estimated Fair Value	193,999	53,341
Total
Amortized Cost	668,310
Unrealized Gain	24	1
Unrealized Loss	(41)	(2)
Estimated Fair Value	668,293
Commercial paper
Marketable securities:
Amortized Cost	83,728	27,473
Unrealized Gain	0	0
Unrealized Loss	0	0
Estimated Fair Value	83,728	27,473
Total
Unrealized Gain	0	0
Unrealized Loss	0	0
Corporate securities
Marketable securities:
Amortized Cost	78,353	6,940
Unrealized Gain	24	0
Unrealized Loss	(14)	(2)
Estimated Fair Value	78,363	6,938
Total
Unrealized Gain	24	0
Unrealized Loss	(14)	(2)
U.S. Treasury securities
Marketable securities:
Amortized Cost	15,200	16,157
Unrealized Gain	0	1
Unrealized Loss	(12)	0
Estimated Fair Value	15,188	16,158
Total
Unrealized Gain	0	1
Unrealized Loss	(12)	0
Asset-backed securities
Marketable securities:
Amortized Cost	16,735	2,772
Unrealized Gain	0	0
Unrealized Loss	(15)	0
Estimated Fair Value	16,720	2,772
Total
Unrealized Gain	0	0
Unrealized Loss	(15)	0
Money market funds
Cash equivalents:
Amortized Cost	474,294	28,371
Estimated Fair Value	$ 474,294	28,371
Total
Amortized Cost		81,713
Estimated Fair Value		$ 81,712

Cash Equivalents and Marketab_4

Cash Equivalents and Marketable Securities - Maturities of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Due within one year	$ 137,077	$ 53,342
Due after one to four years	56,939
Total	194,016
Estimated Fair Value
Due within one year	137,043	$ 53,341
Due after one to four years	56,956
Total	$ 193,999

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - Fair Value, Recurring - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 668,293,000	$ 81,712,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	$ 0
Financial liabilities	$ 0

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 474,294	$ 28,371
Marketable securities	193,999	53,341
Total cash equivalents and marketable securities	668,293	81,712
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	83,728	27,473
Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	78,363	6,938
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	15,188	16,158
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	16,720	2,772
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	474,294	28,371
Marketable securities	0	0
Total cash equivalents and marketable securities	474,294	28,371
Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Level 1 | Corporate securities
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 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities	193,999	53,341
Total cash equivalents and marketable securities	193,999	53,341
Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	83,728	27,473
Level 2 | Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	78,363	6,938
Level 2 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	15,188	16,158
Level 2 | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 16,720	$ 2,772

Other Balance Sheet Component_2

Other Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 16,668	$ 7,868
Less: accumulated depreciation and amortization	(4,123)	(2,150)
Property and equipment, net	12,545	5,718
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,123	2,002
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,201	1,174
Capitalized internal-use software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,842	1,842
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 9,502	$ 2,850

Other Balance Sheet Component_3

Other Balance Sheet Components - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Depreciation and amortization expense related to property and equipment	$ 2	$ 1
Amortization related to intangible assets	$ 2.2	$ 2.1

Other Balance Sheet Component_4

Other Balance Sheet Components - Intangible Assets, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 11,668	$ 11,668
Accumulated Amortization	(6,833)	(4,681)
Net Carrying Amount	$ 4,835	$ 6,987
Weighted Average Remaining Life (years)	2 years 9 months 18 days	3 years 3 months 18 days
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 7,068	$ 7,068
Accumulated Amortization	(4,684)	(3,451)
Net Carrying Amount	$ 2,384	$ 3,617
Weighted Average Remaining Life (years)	3 years	3 years
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4,600	$ 4,600
Accumulated Amortization	(2,149)	(1,230)
Net Carrying Amount	$ 2,451	$ 3,370
Weighted Average Remaining Life (years)	2 years 8 months 12 days	3 years 8 months 12 days

Other Balance Sheet Component_5

Other Balance Sheet Components - Expected Future Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
2022	$ 1,773
2023	1,773
2024	1,054
2025	235
Thereafter	0
Net Carrying Amount	$ 4,835	$ 6,987

Other Balance Sheet Component_6

Other Balance Sheet Components - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued compensation	$ 3,375	$ 6,888
Liability for early exercise of unvested stock options	690	1,133
Taxes payable	879	516
Deferred revenue	3,388	2,585
Other accrued and current liabilities	7,112	3,876
Accrued expenses and other current liabilities	$ 15,444	$ 14,998

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease cost	$ 9,864	$ 6,278
Short-term lease cost	525	495
Variable lease cost	409	452
Total	$ 10,798	$ 7,225

Leases - Other Lease Informatio

Leases - Other Lease Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 6,585	$ 5,624
ROU assets obtained in exchange for lease obligations:
Operating leases	$ 28,252	$ 39,664
Weighted average remaining lease term (years)	7 years 3 months 18 days	8 years 2 months 12 days
Weighted average discount rate (as a percent)	4.50%	5.30%

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
2022	$ 10,045
2023	10,347
2024	10,657
2025	10,977
2026	11,306
Thereafter	27,697
Total lease payments	81,029
Less: imputed interest	(12,300)
Present value of lease liabilities	68,729
Less: current operating lease liabilities	(7,131)	$ (3,348)
Long-term operating lease liabilities	$ 61,598	$ 36,254

Commitments and Contingencies_2

Commitments and Contingencies (Details) $ in Thousands	Dec. 31, 2021USD ($)
Commitments and Contingencies Disclosure [Abstract]
2022	$ 18,978
2023	22,528
2024	10,417
Thereafter	0
Total	$ 51,923

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit) - Additional Information (Details) $ / shares in Units, $ in Thousands	Nov. 05, 2021shares	Mar. 31, 2021	Dec. 31, 2021USD ($)vote$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2018shares
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Recapitalization exchange ratio			3.1057
Preferred stock authorized (in shares)			50,000,000
Preferred stock, par value (in USD per share) | $ / shares			$ 0.0001
Preferred stock issued (in shares)			0
Preferred stock outstanding (in shares)			0
Common stock authorized (in shares)				375,788,212
Current liability related to common stock subject to repurchase | $			$ 700	$ 1,100
Unvested shares of common stock subject to repurchase (in shares)			421,594	692,990
Liability related to restricted stock subject to repurchase | $			$ 4,800	$ 10,500
Stock-based compensation expense | $			$ 47,514	$ 22,608
Shares reserved for issuance (in shares)			138,713,000	250,008,000
Options granted, weighted average grant date fair value (in USD per share) | $ / shares			$ 3.63	$ 2.40
Options vested (in shares)			18,455,667	13,012,287
Weighted average grant-date fair value of options vested (in USD per share) | $ / shares			$ 2.23	$ 1.64
Intrinsic value of options exercised | $			$ 31,900	$ 9,800
Options granted (in shares)			25,262,000
Unrecognized stock-based compensation expense | $			$ 123,200
Unrecognized stock-based compensation expense, expected period of recognition			2 years 4 months 24 days
Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Conversion ratio (in shares)	1
CEO
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Options granted (in shares)			2,308,097
Non-employee
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Options granted (in shares)			19,639
The 2018 Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vesting period				4 years
Shares reserved for issuance (in shares)				4,043,637
The 2021 Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Shares reserved for issuance (in shares)			46,008,885
Increase in number of stock available for grant as a proportion of common stock outstanding (as a percent)			5.00%
Outstanding stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vesting period			4 years
Stock-based compensation expense | $			$ 8,500
Minimum threshold of voting power (as a percent)			10.00%
Minimum proportion of fair market value of stock options granted to grantees that own more than 10% of voting power (as a percent)			110.00%
Expiration period			10 years
Expected dividend yield (as a percent)		0.00%
Unrecognized stock-based compensation expense | $			$ 0
Stock Options - Grantees Owning >10% of Voting Power
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Expiration period			5 years
Unvested restricted stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Awards issued during period (in shares)					15,408,183
Vesting period					48 months
Unvested restricted common stock subject to repurchase (in shares)			3,210,037	7,062,082
Stock-based compensation expense | $			$ 4,600	$ 4,600
Unvested RSUs | The 2018 Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vesting period				4 years
Class A Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized (in shares)			2,500,000,000	0
Number of votes per share | vote			1
Class A Common Stock | Unvested RSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vesting period			4 years
Class A Common Stock | ESPP | The 2021 Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Shares reserved for issuance (in shares)			8,901,159
Class B Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares converted (in shares)	190,477,421
Recapitalization exchange ratio			3.1057
Common stock authorized (in shares)			500,000,000	375,788,000
Number of votes per share | vote			10
Class B Common Stock | ESPP | The 2021 Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Shares reserved for issuance (in shares)			89,011,590
ESPP, purchase price as proportion of common stock price (as a percent)			85.00%
Increase in number of stock available for grant as a proportion of common stock outstanding (as a percent)			1.00%

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit) - Shares Reserved for Future Issuance (Details) - shares shares in Thousands	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Redeemable convertible preferred stock (in shares)	0	190,477
Stock options outstanding (in shares)	58,278	46,973
Unvested restricted stock units (RSUs) (in shares)	2,511	0
Shares reserved for future award issuances (in shares)	77,924	12,558
Total (in shares)	138,713	250,008

Redeemable Convertible Prefer_5

Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit) - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Options
Beginning balance (in shares)	46,973
Options granted (in shares)	25,262
Options exercised (in shares)	(10,325)
Options forfeited or expired (in shares)	(3,632)
Ending balance (in shares)	58,278	46,973
Options vested and exercisable (in shares)	23,443
Weighted- Average Exercise Price
Beginning balance (in USD per share)	$ 1.80
Options granted (in USD per share)	3.05
Options exercised (in USD per share)	1.48
Options forfeited and expired (in USD per share)	2.50
Ending balance (in USD per share)	2.35	$ 1.80
Options vested and exercisable (in USD per share)	$ 1.72
Additional Disclosures
Options outstanding, weighted average remaining contractual term (years)	8 years 1 month 6 days	7 years 9 months 18 days
Options vested and exercisable, weighted average remaining contractual term (years)	6 years 7 months 6 days
Options outstanding, aggregate intrinsic value	$ 322,799	$ 28,467
Options vested and exercisable, aggregate intrinsic value	$ 144,608

Redeemable Convertible Prefer_6

Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit) - Restricted Stock Units (Details) - Restricted Stock Units shares in Thousands	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Number of Shares
Beginning balance (in shares) | shares	0
RSUs granted (in shares) | shares	2,701
RSUs vested (in shares) | shares	(166)
RSUs forfeited (in shares) | shares	(24)
Ending balance (in shares) | shares	2,511
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 0
RSUs granted (in USD per share) | $ / shares	8.74
RSUs vested (in USD per share) | $ / shares	8.91
RSUs forfeited (in USD per share) | $ / shares	7.68
Ending balance (in USD per share) | $ / shares	$ 8.74

Redeemable Convertible Prefer_7

Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit) - Fair Value Assumptions (Details) - Employee and Non-employee Stock Option - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum (as a percent)	53.70%	48.80%
Expected volatility, maximum (as a percent)	54.50%	53.40%
Expected term (years)	6 years 3 months 18 days	6 years
Risk-free interest rate (as a percent)	1.10%	0.60%
Expected dividend yield (as a percent)	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of common stock per share (in USD per share)	$ 4.92	$ 3.89
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of common stock per share (in USD per share)	$ 6.83	$ 4.23

Redeemable Convertible Prefer_8

Redeemable Convertible Preferred Stock, Common Stock, and Stockholders’ Equity (Deficit) - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 47,514	$ 22,608
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	1,466	905
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	20,690	10,235
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	6,388	3,403
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 18,970	$ 8,065

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Narrative (Details)	Dec. 31, 2021
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Recapitalization exchange ratio	3.1057
Class B Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Recapitalization exchange ratio	3.1057

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net loss attributable to common stockholders, basic		$ (75,234)
Net loss attributable to common stockholders, diluted		$ (75,234)
Weighted average shares used in computing net loss per share attributable to common stockholders, basic (in shares)	146,337	90,190
Weighted average shares used in computing net loss per share attributable to common stockholders, diluted (in shares)	146,337	90,190
Net loss per share attributable to common stockholders, basic (in USD per share)	$ (0.65)	$ (0.83)
Net loss per share attributable to common stockholders, diluted (in USD per share)	$ (0.65)	$ (0.83)
Class A Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net loss attributable to common stockholders, basic	$ (8,032)
Net loss attributable to common stockholders, diluted	$ (8,032)
Weighted average shares used in computing net loss per share attributable to common stockholders, basic (in shares)	12,330
Weighted average shares used in computing net loss per share attributable to common stockholders, diluted (in shares)	12,330
Net loss per share attributable to common stockholders, basic (in USD per share)	$ (0.65)
Net loss per share attributable to common stockholders, diluted (in USD per share)	$ (0.65)
Class B Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net loss attributable to common stockholders, basic	$ (87,293)
Net loss attributable to common stockholders, diluted	$ (87,293)
Weighted average shares used in computing net loss per share attributable to common stockholders, basic (in shares)	134,007
Weighted average shares used in computing net loss per share attributable to common stockholders, diluted (in shares)	134,007
Net loss per share attributable to common stockholders, basic (in USD per share)	$ (0.65)
Net loss per share attributable to common stockholders, diluted (in USD per share)	$ (0.65)

Net Loss Per Share Attributab_5

Net Loss Per Share Attributable to Common Stockholders - Potentially Dilutive Securities Outstanding (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	64,602	245,409
Redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	0	190,477
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	58,278	46,973
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	2,511	0
Unvested early exercised stock options subject to repurchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	422	693
Unvested restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	3,210	7,062
Contingently issuable shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	181	204

Employee Benefit Plan (Details)

Employee Benefit Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Retirement Benefits [Abstract]
Employer matching contribution cost	$ 1,100,000	$ 0
Employed discretionary contribution amount	$ 0

Income Taxes - Loss Before Inco

Income Taxes - Loss Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Domestic	$ (94,693)	$ (74,882)
Foreign	(475)	(225)
Loss before income taxes	$ (95,168)	$ (75,107)

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Current:
Federal	$ 0	$ 0
State	146	11
Foreign	11	116
Total current provision for income taxes	157	127
Deferred:
Federal	0	0
State	0	0
Foreign	0	0
Total deferred provision for income taxes	0	0
Total provision for income taxes	$ 157	$ 127

Income Taxes - Effective Tax Ra

Income Taxes - Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Statutory rate	(21.00%)	(21.00%)
State tax	0.20%	(2.50%)
Permanent items	0.70%	0.40%
Transaction costs	(4.80%)	0.00%
Stock-based compensation	6.60%	4.30%
R&D credit	(4.20%)	(4.20%)
Other	0.00%	0.10%
Changes in valuation allowance	22.80%	22.90%
Foreign rate differential	(0.10%)	0.20%
Effective tax rate	0.20%	0.20%

Income Taxes - Deferred Taxes (

Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss	$ 96,423	$ 82,031
Credit carryforwards	14,162	10,143
Stock-based compensation	5,924	3,149
Lease liability	16,691	9,288
Reserves, accruals and other	1,774	1,152
Other	331	0
Total deferred tax assets	135,305	105,763
Valuation allowance	(120,873)	(96,044)
Total deferred tax assets, net	14,432	9,719
Deferred tax liabilities:
Fixed asset basis and other	0	(858)
ROU asset basis	(14,432)	(8,861)
Total deferred tax liabilities	(14,432)	(9,719)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Examination [Line Items]
Change in valuation allowance	$ 24,800,000	$ 8,700,000
Gross deferred tax assets	135,305,000	105,763,000
Unrecognized tax benefits that would impact effective tax rate	0
Unrecognized tax benefits	13,902,000	10,143,000	$ 6,971,000
Unrecognized tax benefits, interest and penalties accrued during year	0	0
Unrecognized tax benefits, penalties and interest accrued	0	$ 0
Federal
Income Tax Examination [Line Items]
Operating loss carryforwards	390,000,000
Operating loss carryforwards, carried forward indefinitely	214,100,000
Tax credit carryforward	16,600,000
State
Income Tax Examination [Line Items]
Operating loss carryforwards	226,000,000
Tax credit carryforward	$ 14,200,000

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits - beginning of year	$ 10,143	$ 6,971
Increases related to current year tax positions	3,759	3,129
Increases related to prior year tax positions	0	43
Gross unrecognized tax benefits - end of year	$ 13,902	$ 10,143

Geographical Information - Summ

Geographical Information - Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 192,197	$ 123,284
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	183,724	119,118
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 8,473	$ 4,166