Duolingo (DUOL) 10-Q9 May 232023 Q1 Quarterly reportFinancial data

Company Profile

Cover Page

Cover Page - shares	3 Months Ended
Cover Page - shares	Mar. 31, 2023	May 08, 2023
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2023
Document Transition Report	false
Entity File Number	001-40653
Entity Registrant Name	Duolingo, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	45-3055872
Entity Address, Address Line One	5900 Penn Avenue
Entity Address, City or Town	Pittsburgh
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15206
City Area Code	(412)
Local Phone Number	567-6602
Title of 12(b) Security	Class A common stock, $0.0001 per share
Trading Symbol	DUOL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0001562088
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	false
Common Class A
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		34,735,032
Common Class B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		6,317,657

UNAUDITED CONDENSED CONSOLIDATE

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 641,091	$ 608,180
Accounts receivable	52,509	46,728
Deferred cost of revenues	40,137	35,041
Prepaid expenses and other current assets	7,497	7,234
Total current assets	741,234	697,183
Assets, Noncurrent
Property and equipment, net	12,842	12,969
Goodwill	4,050	4,050
Intangible assets, net	8,475	8,497
Operating lease right-of-use assets	21,779	22,508
Deferred tax assets	633	633
Other assets	1,366	1,507
Total assets	790,379	747,347
Current liabilities
Accounts payable	986	1,177
Deferred revenues	181,942	157,550
Income tax payable	925	1,069
Accrued expenses and other current liabilities	18,960	21,970
Total current liabilities	202,813	181,766
Liabilities, Noncurrent
Long-term obligation under operating leases	22,378	23,503
Total liabilities	225,191	205,269
Commitments and contingencies (Note 8)
Stockholders’ equity
Class A common stock, $0.0001 par value; 2,000,000 shares authorized as of March 31, 2023 and December 31, 2022; 33,800 and 31,899 issued and outstanding at March 31, 2023 and December 31, 2022, respectively Class B common stock, $0.0001 par value; 30,000 shares authorized as of March 31, 2023 and December 31, 2022; 7,218 and 8,462 issued and outstanding at March 31, 2023 and December 31, 2022, respectively	4	4
Additional paid-in capital	798,254	772,562
Accumulated deficit	(233,070)	(230,488)
Total stockholders’ equity	565,188	542,078
Total liabilities and stockholders' equity	$ 790,379	$ 747,347

UNAUDITED CONDENSED CONSOLIDA_2

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2023	Dec. 31, 2022
Common Class A
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, shares issued (in shares)	33,800,000	31,899,000
Common stock, shares outstanding (in shares)	33,800,000	31,899,000
Common Class B
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	30,000,000	30,000,000
Common stock, shares issued (in shares)	7,218,000	8,462,000
Common stock, shares outstanding (in shares)	7,218,000	8,462,000

UNAUDITED CONDENSED CONSOLIDA_3

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Statement [Abstract]
Revenues	$ 115,661	$ 81,220
Cost of revenues	31,492	21,490
Gross profit	84,169	59,730
Operating expenses:
Research and development	45,844	29,781
Sales and marketing	16,601	14,940
General and administrative	30,243	26,856
Total operating expenses	92,688	71,577
Loss from operations	(8,519)	(11,847)
Other income (expense), net	182	(312)
Loss before interest income and (benefit) provision for income taxes	(8,337)	(12,159)
Interest income	5,639	33
Loss before (benefit) provision for income taxes	(2,698)	(12,126)
(Benefit) provision for income taxes	(116)	28
Net loss	(2,582)	(12,154)
Net comprehensive loss	$ (2,582)	$ (12,154)
Net loss per share attributable to Class A and Class B common stockholders, basic (in usd per share)	$ (0.06)	$ (0.31)
Net loss per share attributable to Class A and Class B common stockholders, diluted (in usd per share)	$ (0.06)	$ (0.31)

UNAUDITED CONDENSED CONSOLIDA_4

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2021		38,272
Beginning balance at Dec. 31, 2021	$ 513,056	$ 4	$ 683,966	$ (170,914)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Stock-based compensation	14,586		14,586
Stock options exercised (in shares)		756
Stock options exercised	$ 5,226		5,226
Release of restricted stock units (in shares)	49
Release of restricted stock units	$ 0
Net loss	(12,154)			(12,154)
Ending balance (in shares) at Mar. 31, 2022		39,077
Ending balance at Mar. 31, 2022	520,714	$ 4	703,778	(183,068)
Beginning balance (in shares) at Dec. 31, 2022		40,361
Beginning balance at Dec. 31, 2022	542,078	$ 4	772,562	(230,488)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Stock-based compensation	$ 21,073		21,073
Stock options exercised (in shares)	542	542
Stock options exercised	$ 4,619		4,619
Release of restricted stock units (in shares)		115
Release of restricted stock units	0
Net loss	(2,582)			(2,582)
Ending balance (in shares) at Mar. 31, 2023		41,018
Ending balance at Mar. 31, 2023	$ 565,188	$ 4	$ 798,254	$ (233,070)

UNAUDITED CONDENSED CONSOLIDA_5

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net loss	$ (2,582)	$ (12,154)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	1,762	774
Stock-based compensation	21,073	14,586
Gain on sale of capitalized software	(100)	0
Changes in assets and liabilities:
Deferred revenue	24,392	20,834
Accounts receivable	(5,781)	4,590
Deferred cost of revenues	(5,096)	(3,561)
Prepaid expenses and other current assets	(263)	66
Accounts payable	(345)	(5,800)
Accrued expenses and other current liabilities	(3,201)	1,265
Noncurrent assets and liabilities	(255)	27
Net cash provided by operating activities	29,604	20,627
Cash flows from investing activities:
Capitalized software expense and purchases of intangible assets	(731)	(1,117)
Purchase of property and equipment	(681)	(1,327)
Proceeds from sale of capitalized software	100	0
Net cash used for investing activities	(1,312)	(2,444)
Cash flows from financing activities:
Proceeds from exercise of stock options	4,619	5,226
Net cash provided by financing activities	4,619	5,226
Net increase in cash and cash equivalents	32,911	23,409
Cash and cash equivalents - Beginning of period	608,180	553,922
Cash and cash equivalents - End of period	641,091	577,331
Supplemental disclosure of cash flow information:
Cash paid for interest	0	0
Cash paid for income taxes	28	3
Supplemental disclosure of noncash operating activities:
Implementation costs for cloud computing included in Current liabilities	0	153
Supplemental disclosure of noncash investing activities and financing activities:
Capitalized software and purchases of intangible assets included in Current liabilities	0	14
Property and equipment included in Current liabilities	201	178
Landlord incentive included in Prepaid expenses and other current assets	$ 0	$ 1,102

DESCRIPTION OF THE BUSINESS AND

DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION	3 Months Ended
DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION	DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION Duolingo, Inc. (the “Company” or “Duolingo”) was formed on August 18, 2011, and the Duolingo app was launched to the general public on June 19, 2012. The Company’s headquarters are located in Pittsburgh, Pennsylvania. Duolingo is a US-based mobile learning platform, as well as a digital language proficiency assessment exam. The Company has a freemium business model: the app and the website are accessible free of charge, although Duolingo also offers premium services for a subscription fee. As of the date of this filing, Duolingo offers courses in over 40 different languages, including Spanish, English, French, German, Italian, Portuguese, Japanese and Chinese. We have locations in the United States, China and Germany. Principles of Consolidation —The Unaudited Condensed Consolidated Financial Statements include the accounts of the Company and subsidiaries over which the Company has control. All intercompany transactions and balances have been eliminated. Basis of Presentation —The accompanying Unaudited Condensed Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) from the Company’s accounting records and reflect the consolidated financial position and results of operations for the three months ended March 31, 2023 and 2022. Unless otherwise specified, all dollar amounts are referred to in thousands. The Unaudited Condensed Consolidated Financial Statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such SEC rules. We believe that the disclosures made are adequate to make the information presented not misleading. In our opinion, all adjustments considered necessary for a fair presentation of the financial statements have been included, and all adjustments are of a normal and recurring nature. We consistently applied the accounting policies consistent with the annual Unaudited Condensed Consolidated Financial Statements elsewhere in this Quarterly Report on Form 10-Q, in preparing these Unaudited Condensed Consolidated Financial Statements. These Unaudited Condensed Consolidated Financial Statements should be read in conjunction with the audited financial statements and the notes for the fiscal year ended December 31, 2022 included in the Annual Report on Form 10-K and filed with the SEC.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Mar. 31, 2023
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Accounting Principles —The Unaudited Condensed Consolidated Financial Statements and accompanying notes are prepared in accordance with GAAP. Use of Estimates— The preparation of Unaudited Condensed Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Unaudited Condensed Consolidated Financial Statements and accompanying notes. Significant estimates and assumptions reflected in the Unaudited Condensed Consolidated Financial Statements include, but are not limited to, useful lives of property and equipment, valuation of deferred tax assets and liabilities, stock-based compensation, common stock valuation, operating lease right-of-use assets and liabilities, capitalization of internally developed software and associated useful lives and contingent liabilities. Actual results may differ materially from such estimates. Management believes that the estimates, and judgments upon which they rely, are reasonable based upon information available to them at the time that these estimates and judgments are made. To the extent that there are material differences between these estimates and actual results, the Company’s Unaudited Condensed Consolidated Financial Statements will be affected. Cash and Cash Equivalents— Cash consists primarily of cash on hand and bank deposits. Cash equivalents consist primarily of money market accounts with maturities of three months or less at the date of acquisition and are stated at cost, which approximates fair value. The Company maintains cash deposits with financial institutions that may exceed federally insured limits at times. The following table shows the breakout between cash and money market funds. March 31, December 31, Cash $ 48,462 $ 91,189 Money market funds 592,629 516,991 Total $ 641,091 $ 608,180 The Money market funds are considered Level 1 financial assets. Level 1 financial assets use inputs that are the unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Advertising Costs — Advertising costs were approximately $11,093 and $10,954 for the three months ended March 31, 2023 and 2022, respectively, and are included within Sales and marketing in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss. Income Taxes— The Company’s provision for income taxes is computed by using an estimate of the annual effective tax rate, adjusted for discrete items taken into account in the relevant period, if any. Each quarter, the annual effective income tax rate is recomputed and if there are material changes in the estimate, a cumulative adjustment is made. Concentration of Credit Risk —The Company’s concentration of credit risk relates to financial institutions holding the Company’s cash and cash equivalents and platforms with significant accounts receivable balances and revenue transactions. The Company maintains cash deposits with financial institutions that may exceed federally insured limits at times. Management believes that the financial institutions that hold the Company’s deposits are financially credit worthy and, accordingly, minimal credit risk exists with respect to those balances. The majority of our revenue comes through our subscriptions and advertising streams and payments are made to Duolingo through service providers. The top three service providers, Apple, Google and Stripe accounted for 66.9%, 19.3% and 10.0% of total Accounts receivable as of March 31, 2023, respectively. The top two service providers, Apple and Google, accounted for 56.2% and 27.5% of total Accounts receivable as of December 31, 2022, respectively. Three service providers, Apple, Google and Stripe processed 57.1%, 26.2% and 11.9% of total Revenues for the three months ended March 31, 2023, respectively. Two services providers, Apple and Google, processed 51.1% and 29.1% of total Revenues for the three months ended March 31, 2022, respectively. Impairment of long-lived assets— The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If the sum of the estimated undiscounted future cash flows expected to result from the use and eventual disposition of an asset is less than the carrying amount of the asset, an impairment loss is recognized. Measurement of an impairment loss is based on the fair value of the asset. No assets were impaired during the three months ended March 31, 2023 and 2022. Recently Issued Pronouncements Not Yet Adopted There are no recently issued accounting pronouncements that the Company has not yet adopted that they believe are applicable or would have a material impact on the financial statements of the Company. Recently Adopted Accounting Pronouncements There are no recently adopted accounting pronouncements.

REVENUE

REVENUE	3 Months Ended
REVENUE	Mar. 31, 2023
Revenue from Contract with Customer [Abstract]
REVENUE	REVENUE The Company has three predominant sources of revenues; time-based subscriptions, in-app advertising placement by third parties, and the Duolingo English Test. Revenue is recognized upon transfer of control of promised products or services to users in an amount that reflects the consideration the Company expects to receive in exchange for those services. The Company does not enter into contracts with a customer that contain multiple promises that result in multiple performance obligations. Revenue is recorded net of taxes assessed by a government authority that are both imposed on and concurrent with specific revenue transactions between us and our users. Revenue from time-based subscriptions includes a stand-ready obligation to provide hosting services that are consumed by the customer over the subscription period. Users can purchase Duolingo monthly or they can purchase a six-month or year-long subscription and pay for the subscription at the time of purchase. Under the year-long subscription, users can also purchase a single plan or a family plan. The family plan includes up to six users on one subscription. Such payments are initially recorded to deferred revenue. The user has the ability to download limited content offline. However, as there is a significant level of integration and interdependency with the online functionality, the Company considers the service to be a single performance obligation for the online and offline content. The Company enters into arrangements with advertising networks to monetize the in-app advertising inventory. Revenue from in-app advertising placement is recognized at a point in time when the advertisement is placed and is based upon the amount received. Duolingo English Test revenue is generally recognized once the tests have gone through the proctoring process and a certification decision has been made. This process usually takes less than 48 hours after the test has been completed and uploaded. Customers have 21 days from the date of purchase to take the exam or their purchase will expire and revenue will be recognized. Virtually all customers complete their exams prior to expiration. Sometimes organizations may purchase tests in bulk via coupons with a one year expiration date. The Company will defer revenue from all tests that have neither been proctored nor expired. The Company’s users have the option to purchase consumable in-app virtual goods. The Company recognizes revenue over the period in which the user consumes the virtual good, which is generally within a month. The Company also recognizes revenue from Duo’s Taquería , a restaurant that opened during 2022, in the space adjacent to our headquarters in Pittsburgh. Revenue from Duo’s Taquería is recognized at a point in time when the sales are made. Principal Agent Considerations —The Company makes its application available to be downloaded through third-party digital distribution service providers. Users who purchase subscriptions also pay through the respective app stores. The Company evaluates the purchases via third-party payment processors to determine whether its revenues should be reported gross or net of fees retained by the payment processor. The Company is the principal in the transaction with the end user as a result of controlling, hosting, and integrating the delivery of the virtual items to the end user. The Company records revenue gross as a principal and records fees paid to third-party payment processors as Cost of revenues. Contract Balances —Deferred revenue mostly consists of payments we receive in advance of revenue recognition, and is mostly related to time-based subscriptions, which will be recognized into revenue over the course of the upcoming year (recognized over 12 months or less). Additionally, the Duolingo English Test has deferred revenue related to tests that have been purchased, but will not be recognized until the tests have been proctored. Disaggregation of Revenue In accordance with ASC 606, Revenue from Contracts with Customers , the Company disaggregates revenue from contracts with customers into revenue stream, which most closely depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. Three Months Ended March 31, 2023 2022 Revenues: Subscription $ 86,185 $ 58,010 Advertising 11,635 11,748 Duolingo English Test 9,972 8,080 Other (1) 7,869 3,382 Total revenues $ 115,661 $ 81,220 ________________ (1) Other revenue is mainly comprised of in-app purchases of virtual goods. Changes in deferred revenues were as follows: Three Months Ended March 31, 2023 2022 Beginning balance—January 1 $ 157,550 $ 98,267 Amount from beginning balance recognized into revenue (65,492) (40,474) Recognition of deferred revenue (30,129) (22,195) Deferral of revenue 120,013 83,503 Ending balance—March 31 $ 181,942 $ 119,101

PROPERTY and EQUIPMENT, net

PROPERTY and EQUIPMENT, net	3 Months Ended
PROPERTY and EQUIPMENT, net	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
PROPERTY and EQUIPMENT, net	PROPERTY and EQUIPMENT, net Property and equipment consists of the following as of March 31, 2023 and December 31, 2022: 2023 2022 Leasehold improvements $ 16,693 $ 15,983 Furniture, fixtures and equipment 5,376 5,204 Total property and equipment 22,069 21,187 Less: accumulated depreciation (9,227) (8,218) Total property and equipment, net $ 12,842 $ 12,969 Depreciation expense is included within the following financial statement line items within the Company’s Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss. Three Months Ended March 31, (In thousands) 2023 2022 Research and development $ 407 $ 134 Sales and marketing 48 19 General and administrative 554 412 Total $ 1,009 $ 565

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL	3 Months Ended
INTANGIBLE ASSETS AND GOODWILL	Mar. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS AND GOODWILL	INTANGIBLE ASSETS AND GOODWILL Intangible assets consist mostly of capitalized software, with $18 of other intangible assets as of March 31, 2023 and December 31, 2022. 2023 2022 Intangible assets $ 17,250 $ 16,827 Less: accumulated amortization (8,775) (8,330) Intangible assets, net $ 8,475 $ 8,497 The Company capitalized $731 and $1,131 of software development costs during the three months ended March 31, 2023 and 2022, respectively. Amortization expense is included within the following financial statement line items within the Company’s Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss Three Months Ended March 31, (In thousands) 2023 2022 Cost of revenues $ 403 $ — Sales and marketing 350 209 Total $ 753 $ 209

INCOME TAXES

INCOME TAXES	3 Months Ended
INCOME TAXES	Mar. 31, 2023
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Year-to-date income tax expense or benefit is the product of the most current projected annual effective tax rate (“PAETR”) and the actual year-to-date pretax income (loss) adjusted for any discrete items. The income tax expense or benefit for a particular quarter, is the difference between the year-to-date calculation of income tax expense or benefit and the year-to-date calculation for the prior quarter. Items unrelated to current period ordinary income or (loss) are recognized entirely in the period identified as a discrete item of tax. The Company’s PAETR was lower than the US federal statutory rate of 21.0% during the three months ended March 31, 2023 and 2022 primarily due to the impact of maintaining a US valuation allowance provided on US deferred tax assets. The Company continues to maintain a full valuation allowance on US federal and state net deferred tax assets for the period ending March 31, 2023 as a result of pre-tax losses incurred since the Company’s inception in early 2012. The Company is projecting pre-tax loss in 2023. Current and Prior Period Tax Expense The Company’s income before taxes, income tax provision or benefit and effective tax rates were as follows: Three Months Ended March 31, (In thousands, except percentages) 2023 2022 Loss before (benefit) provision for income taxes $ (2,698) $ (12,126) (Benefit) provision for income taxes (116) 28 Effective tax rate 4.3 % (0.2) % The change in the effective tax rate from the prior year was primarily due to increased tax benefits related to stock-based compensation.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	3 Months Ended
STOCK-BASED COMPENSATION	Mar. 31, 2023
Equity [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Prior to the IPO, the Company granted options to purchase shares of the Company’s common stock and restricted stock units (“RSU”) in respect of shares of the Company’s common stock to employees, directors and consultants under the Company’s 2011 Equity Incentive Plan. In July 2021, Duolingo adopted the 2021 Incentive Award Plan (“2021 Plan”) and the 2021 Employee Stock Purchase Plan (“ESPP”), each of which became effective on July 26, 2021 in connection with the IPO. An aggregate of 7,946 shares and 1,119 shares of Class A common stock were made available for future issuance under the 2021 Plan and ESPP, respectively. On each January 1, the number of shares of the Company’s Class A common stock available for issuance under the 2021 Plan have been, and through January 1, 2031, will be, increased by the lesser of (i) 5% of the shares outstanding on the preceding December 31 (calculated on an as-converted basis) and (B) such smaller number of shares of common stock as determined by the Board or the Committee (as defined in the 2021 Plan). On January 1, 2023, the 2021 Plan and ESPP were increased by 2,018 shares and 319 shares, respectively. The Company’s stock options vest based on terms in the stock option agreements, which generally provide for vesting over four years based on continued service to the Company and its subsidiaries. Each option has a term of ten years. Stock options granted under the 2021 Plan must generally have an exercise price of not less than the estimated fair market value of the underlying Class A common stock at the date of the grant. No options have been granted under the 2021 Plan. A summary of stock option activity under the Plans was as follows: Number of Weighted- Weighted- average remaining contractual life (years) Aggregate intrinsic value Options outstanding at January 1, 2023 4,410 $ 14.04 6.25 $ 251,832 Granted (1) — Exercised (542) 8.57 Forfeited and expired (3) 22.37 Options outstanding at March 31, 2023 3,865 $ 14.80 6.17 $ 493,610 Options exercisable at March 31, 2023 3,297 $ 14.05 6.00 $ 423,829 ________________ (1) There were no stock options granted during the three months ended March 31, 2023 and 2022. The total intrinsic value of options exercised was approximately $55,062 and $60,334 for the periods ended March 31, 2023 and 2022, respectively. A summary of RSU activity under the Plans was as follows: Restricted stock units Weighted- Outstanding at January 1, 2023 2,036 $ 85.74 Granted 185 97.62 Released (115) 84.18 Forfeited (58) 97.80 Outstanding at March 31, 2023 2,048 $ 86.56 As of March 31, 2023, there was approximately $4,522 of unrecognized compensation cost related to stock options granted under the plans with a weighted-average period of approximately one year. The amount of unrecognized compensation expense for RSUs as of March 31, 2023 was $163,373 with a weighted-average period of approximately three years, for a total unrecognized compensation expense of $167,895. There were 10,011 shares available for grant at March 31, 2023. Performance-based RSUs In June 2021, the Company granted an aggregate of 1,800 performance-based RSUs (the “Founder Awards”) to the Company’s founders. The Founder Awards vest upon the satisfaction of both a service-based condition and a performance-based condition and generally are settled one year after vesting. The service-based condition is satisfied as to 25% of the Founder Awards on each anniversary of the completion of the IPO, subject to the continuous service of the founders through the applicable date. The performance-based condition will be satisfied with respect to each of 10 equal tranches only if the trailing 60-calendar day volume-weighted-average closing trading price of the Company’s Class A common stock reaches certain stock-price hurdles for each such tranche, as set forth below, over a period of 10 years from the date of grant. Any RSUs associated with stock-prices hurdle not achieved by the tenth anniversary of the date of grant will terminate and be canceled for no additional consideration to the founders. The stock-price hurdles and number of RSUs eligible to vest will be adjusted to reflect any stock splits, stock dividends, combinations, reorganizations, reclassifications, or similar events under the 2021 Plan. The Founder Awards will be settled in shares of the Company’s Class B common stock. Tranche Company Stock Price Hurdle Number of RSUs Eligible to Vest 1 $ 127.50 90 2 $ 153.00 90 3 $ 178.50 90 4 $ 204.00 180 5 $ 255.00 180 6 $ 306.00 180 7 $ 357.00 180 8 $ 408.00 180 9 $ 612.00 270 10 $ 816.00 360 The Company estimated the grant date fair value of the Founder Awards using a model based on multiple stock-price paths developed through the use of a Monte Carlo simulation that incorporates into the valuation the possibility that the stock-price hurdles may not be satisfied. The weighted-average grant date fair value of the Founder Awards was estimated to be $61.56 per share and the Company estimates that it will recognize total stock-based compensation expense of approximately $110,817 over the derived service period of each of the ten separate tranches which is between 3.58 – 5.92 years. If the stock-price hurdles are met sooner than the requisite service period, the stock-based compensation expense will be adjusted to prospectively recognize the remaining expense over the remaining derived service period. Provided that the founders continue to provide services to the Company, stock-based compensation expense is recognized over the derived service period, regardless of whether the stock-price hurdles are achieved. The stock-price hurdles for the first two tranches were met during 2021. No additional stock-price hurdles have been met since. The Company recognized $7,140 and $8,019 of stock-based compensation expense related to these awards for the three months ended March 31, 2023 and 2022, respectively, which is included within General and administrative in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss. As of March 31, 2023, there is $56,217 of unrecognized compensation expense related to these awards. Total stock-based compensation expense was $21,073 and $14,586 for the three months ended March 31, 2023 and 2022, respectively. Stock based compensation expense is included in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss as shown in the following table: Three Months Ended March 31, 2023 2022 Cost of revenues $ 11 $ 6 Research and development 9,346 3,632 Sales and marketing 779 348 General and administrative 10,937 10,600 Total $ 21,073 $ 14,586 Nominal amounts of stock based compensation expense is capitalized into intangible assets for the three months ended March 31, 2023 and 2022.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Legal Proceedings — From time to time, the Company may become involved in various legal proceedings in the ordinary course of its business and may be subject to third-party infringement claims. The outcome of any such claims or proceedings, regardless of the merits, is inherently uncertain. The Company is not currently party to any material legal proceedings. Related Parties — The Company has determined that there were no transactions with related parties as of or during the three months ended March 31, 2023 and 2022.

ACCRUED EXPENSES AND OTHER CURR

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	3 Months Ended
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	Mar. 31, 2023
Other Liabilities Disclosure [Abstract]
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities consisted of the following: March 31, December 31, 2022 Obligations under current leases $ 5,524 $ 4,903 Marketing related accruals 2,726 3,464 Sales and VAT tax accrual 2,421 2,396 Employee-related costs 1,938 4,233 Other 6,351 6,974 Total $ 18,960 $ 21,970

EMPLOYEE BENEFIT PLAN

EMPLOYEE BENEFIT PLAN	3 Months Ended
EMPLOYEE BENEFIT PLAN	Mar. 31, 2023
Postemployment Benefits [Abstract]
EMPLOYEE BENEFIT PLAN	EMPLOYEE BENEFIT PLANThe Company sponsors a profit sharing plan with a 401(k) feature, the Duolingo Retirement Plan, (the “Plan”) for eligible employees. The current Plan, effective January 1, 2021, provides for Company safe harbor matching contributions of 100% of the first 4% of the employees’ elective deferrals and 50% of the next 2%, with vesting starting upon the first day of employment. The Company also has the option to make discretionary matching or profit sharing contributions. The Company made safe harbor matching contributions of approximately $1,397 and $983 for the three months ended March 31, 2023 and 2022, respectively. The Company did not make any discretionary matching or profit sharing contributions during the three months ended March 31, 2023 and 2022.

LOSS PER SHARE

LOSS PER SHARE	3 Months Ended
LOSS PER SHARE	Mar. 31, 2023
Earnings Per Share [Abstract]
LOSS PER SHARE	LOSS PER SHARE Basic and diluted net loss per share attributable to common stockholders is presented in conformity with the two-class method required for participating securities. Basic net loss per share attributable to common stockholders is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, less shares subject to repurchase. The diluted net loss per share attributable to common stockholders is calculated by giving effect to all potential dilutive common stock equivalents outstanding for the period. Three Months Ended March 31, (In thousands, except per share data) 2023 2022 Numerator: Net loss attributable to Class A and Class B common stockholders $ (2,582) $ (12,154) Denominator: Weighted-average shares in computing net loss per share attributable to Class A and Class B common stockholders, basic and diluted 40,618 38,590 Basic loss per common share $ (0.06) $ (0.31) Diluted loss per common share $ (0.06) $ (0.31) The rights, including the liquidation and dividend rights, of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to 20 votes per share. Each share of Class B common stock is convertible into a share of Class A common stock voluntarily at any time by the holder, and automatically upon certain events. The Class A common stock has no conversion rights. As the liquidation and dividend rights are identical for Class A and Class B common stock, the undistributed earnings are allocated on a proportional basis and the resulting net loss per share attributable to common stockholders will, therefore, be the same for both Class A and Class B common stock on an individual or combined basis. Since the Company was in a net loss position for the three months ended March 31, 2023 and 2022, there is no difference between the number of shares used to calculate basic and diluted loss per share. The potential shares of common stock that were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been antidilutive are as follows: Three Months Ended March 31, (in thousands) 2023 2022 Founder awards where performance has been met 180 180 Stock options outstanding (1) 3,865 5,435 RSUs outstanding (1) 2,048 756 Total 6,093 6,371 ________________ (1) Prior year amounts were adjusted in the current year table to include unvested options and RSUs. Founder awards of 1,620, where the performance criteria has not been satisfied, are excluded from the above table because the stock-price hurdles for those awards had not been met as of March 31, 2023 and 2022.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
SUBSEQUENT EVENTS	Mar. 31, 2023
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTSNone

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Mar. 31, 2023
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation—The Unaudited Condensed Consolidated Financial Statements include the accounts of the Company and subsidiaries over which the Company has control. All intercompany transactions and balances have been eliminated.
Basis of Presentation and Accounting Principles	Basis of Presentation—The accompanying Unaudited Condensed Consolidated Financial Statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) from the Company’s accounting records and reflect the consolidated financial position and results of operations for the three months ended March 31, 2023 and 2022. Unless otherwise specified, all dollar amounts are referred to in thousands. Accounting Principles —The Unaudited Condensed Consolidated Financial Statements and accompanying notes are prepared in accordance with GAAP.
Use of Estimates	Use of Estimates— The preparation of Unaudited Condensed Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Unaudited Condensed Consolidated Financial Statements and accompanying notes. Significant estimates and assumptions reflected in the Unaudited Condensed Consolidated Financial Statements include, but are not limited to, useful lives of property and equipment, valuation of deferred tax assets and liabilities, stock-based compensation, common stock valuation, operating lease right-of-use assets and liabilities, capitalization of internally developed software and associated useful lives and contingent liabilities. Actual results may differ materially from such estimates. Management believes that the estimates, and judgments upon which they rely, are reasonable based upon information available to
Cash and Cash Equivalents	Cash and Cash Equivalents—Cash consists primarily of cash on hand and bank deposits. Cash equivalents consist primarily of money market accounts with maturities of three months or less at the date of acquisition and are stated at cost, which approximates fair value. The Company maintains cash deposits with financial institutions that may exceed federally insured limits at times.The Money market funds are considered Level 1 financial assets. Level 1 financial assets use inputs that are the unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.
Advertising Costs	Advertising Costs — Advertising costs were approximately $11,093 and $10,954 for the three months ended March 31, 2023 and 2022, respectively, and are included within Sales and marketing in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss.
Income Taxes	Income Taxes— The Company’s provision for income taxes is computed by using an estimate of the annual effective tax rate, adjusted for discrete items taken into account in the relevant period, if any. Each quarter, the annual effective income tax rate is recomputed and if there are material changes in the estimate, a cumulative adjustment is made.
Concentration of Credit Risk	Concentration of Credit Risk —The Company’s concentration of credit risk relates to financial institutions holding the Company’s cash and cash equivalents and platforms with significant accounts receivable balances and revenue transactions.
Impairment of long-lived assets	Impairment of long-lived assets— The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If the sum of the estimated undiscounted future cash flows expected to result from the use and eventual disposition of an asset is less than the carrying amount of the asset, an impairment loss is recognized. Measurement of an impairment loss is based on the fair value of the asset.
Recently Issued Pronouncements Not Yet Adopted and Recently Adopted Accounting Pronouncements	Recently Issued Pronouncements Not Yet Adopted There are no recently issued accounting pronouncements that the Company has not yet adopted that they believe are applicable or would have a material impact on the financial statements of the Company. Recently Adopted Accounting Pronouncements There are no recently adopted accounting pronouncements.
Revenue	REVENUE The Company has three predominant sources of revenues; time-based subscriptions, in-app advertising placement by third parties, and the Duolingo English Test. Revenue is recognized upon transfer of control of promised products or services to users in an amount that reflects the consideration the Company expects to receive in exchange for those services. The Company does not enter into contracts with a customer that contain multiple promises that result in multiple performance obligations. Revenue is recorded net of taxes assessed by a government authority that are both imposed on and concurrent with specific revenue transactions between us and our users. Revenue from time-based subscriptions includes a stand-ready obligation to provide hosting services that are consumed by the customer over the subscription period. Users can purchase Duolingo monthly or they can purchase a six-month or year-long subscription and pay for the subscription at the time of purchase. Under the year-long subscription, users can also purchase a single plan or a family plan. The family plan includes up to six users on one subscription. Such payments are initially recorded to deferred revenue. The user has the ability to download limited content offline. However, as there is a significant level of integration and interdependency with the online functionality, the Company considers the service to be a single performance obligation for the online and offline content. The Company enters into arrangements with advertising networks to monetize the in-app advertising inventory. Revenue from in-app advertising placement is recognized at a point in time when the advertisement is placed and is based upon the amount received. Duolingo English Test revenue is generally recognized once the tests have gone through the proctoring process and a certification decision has been made. This process usually takes less than 48 hours after the test has been completed and uploaded. Customers have 21 days from the date of purchase to take the exam or their purchase will expire and revenue will be recognized. Virtually all customers complete their exams prior to expiration. Sometimes organizations may purchase tests in bulk via coupons with a one year expiration date. The Company will defer revenue from all tests that have neither been proctored nor expired. The Company’s users have the option to purchase consumable in-app virtual goods. The Company recognizes revenue over the period in which the user consumes the virtual good, which is generally within a month. The Company also recognizes revenue from Duo’s Taquería , a restaurant that opened during 2022, in the space adjacent to our headquarters in Pittsburgh. Revenue from Duo’s Taquería is recognized at a point in time when the sales are made. Principal Agent Considerations —The Company makes its application available to be downloaded through third-party digital distribution service providers. Users who purchase subscriptions also pay through the respective app stores. The Company evaluates the purchases via third-party payment processors to determine whether its revenues should be reported gross or net of fees retained by the payment processor. The Company is the principal in the transaction with the end user as a result of controlling, hosting, and integrating the delivery of the virtual items to the end user. The Company records revenue gross as a principal and records fees paid to third-party payment processors as Cost of revenues. Contract Balances —Deferred revenue mostly consists of payments we receive in advance of revenue recognition, and is mostly related to time-based subscriptions, which will be recognized into revenue over the course of the upcoming year (recognized over 12 months or less). Additionally, the Duolingo English Test has deferred revenue related to tests that have been purchased, but will not be recognized until the tests have been proctored. Disaggregation of Revenue In accordance with ASC 606, Revenue from Contracts with Customers , the Company disaggregates revenue from contracts with customers into revenue stream, which most closely depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	Mar. 31, 2023
Accounting Policies [Abstract]
Schedule of Cash and Cash Equivalents	The following table shows the breakout between cash and money market funds. March 31, December 31, Cash $ 48,462 $ 91,189 Money market funds 592,629 516,991 Total $ 641,091 $ 608,180

REVENUE (Tables)

REVENUE (Tables)	3 Months Ended
REVENUE (Tables)	Mar. 31, 2023
Revenue from Contract with Customer [Abstract]
Schedule of Revenue Sources and Streams	Three Months Ended March 31, 2023 2022 Revenues: Subscription $ 86,185 $ 58,010 Advertising 11,635 11,748 Duolingo English Test 9,972 8,080 Other (1) 7,869 3,382 Total revenues $ 115,661 $ 81,220 ________________ (1) Other revenue is mainly comprised of in-app purchases of virtual goods.
Schedule of Deferred Revenues	Changes in deferred revenues were as follows: Three Months Ended March 31, 2023 2022 Beginning balance—January 1 $ 157,550 $ 98,267 Amount from beginning balance recognized into revenue (65,492) (40,474) Recognition of deferred revenue (30,129) (22,195) Deferral of revenue 120,013 83,503 Ending balance—March 31 $ 181,942 $ 119,101

PROPERTY and EQUIPMENT, net (Ta

PROPERTY and EQUIPMENT, net (Tables)	3 Months Ended
PROPERTY and EQUIPMENT, net (Tables)	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property and equipment consists of the following as of March 31, 2023 and December 31, 2022: 2023 2022 Leasehold improvements $ 16,693 $ 15,983 Furniture, fixtures and equipment 5,376 5,204 Total property and equipment 22,069 21,187 Less: accumulated depreciation (9,227) (8,218) Total property and equipment, net $ 12,842 $ 12,969 Depreciation expense is included within the following financial statement line items within the Company’s Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss. Three Months Ended March 31, (In thousands) 2023 2022 Research and development $ 407 $ 134 Sales and marketing 48 19 General and administrative 554 412 Total $ 1,009 $ 565

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL (Tables)	3 Months Ended
INTANGIBLE ASSETS AND GOODWILL (Tables)	Mar. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Intangible assets consist mostly of capitalized software, with $18 of other intangible assets as of March 31, 2023 and December 31, 2022. 2023 2022 Intangible assets $ 17,250 $ 16,827 Less: accumulated amortization (8,775) (8,330) Intangible assets, net $ 8,475 $ 8,497
Finite-lived Intangible Assets Amortization Expense	Amortization expense is included within the following financial statement line items within the Company’s Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss Three Months Ended March 31, (In thousands) 2023 2022 Cost of revenues $ 403 $ — Sales and marketing 350 209 Total $ 753 $ 209

INCOME TAXES (Tables)

INCOME TAXES (Tables)	3 Months Ended
INCOME TAXES (Tables)	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The Company’s income before taxes, income tax provision or benefit and effective tax rates were as follows: Three Months Ended March 31, (In thousands, except percentages) 2023 2022 Loss before (benefit) provision for income taxes $ (2,698) $ (12,126) (Benefit) provision for income taxes (116) 28 Effective tax rate 4.3 % (0.2) %

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	3 Months Ended
STOCK-BASED COMPENSATION (Tables)	Mar. 31, 2023
Equity [Abstract]
Share-based Payment Arrangement, Option, Activity	A summary of stock option activity under the Plans was as follows: Number of Weighted- Weighted- average remaining contractual life (years) Aggregate intrinsic value Options outstanding at January 1, 2023 4,410 $ 14.04 6.25 $ 251,832 Granted (1) — Exercised (542) 8.57 Forfeited and expired (3) 22.37 Options outstanding at March 31, 2023 3,865 $ 14.80 6.17 $ 493,610 Options exercisable at March 31, 2023 3,297 $ 14.05 6.00 $ 423,829 ________________ (1) There were no stock options granted during the three months ended March 31, 2023 and 2022.
Share-based Payment Arrangement, RSU, Activity	A summary of RSU activity under the Plans was as follows: Restricted stock units Weighted- Outstanding at January 1, 2023 2,036 $ 85.74 Granted 185 97.62 Released (115) 84.18 Forfeited (58) 97.80 Outstanding at March 31, 2023 2,048 $ 86.56
Share-based Payment Arrangement, Payment Award	Tranche Company Stock Price Hurdle Number of RSUs Eligible to Vest 1 $ 127.50 90 2 $ 153.00 90 3 $ 178.50 90 4 $ 204.00 180 5 $ 255.00 180 6 $ 306.00 180 7 $ 357.00 180 8 $ 408.00 180 9 $ 612.00 270 10 $ 816.00 360
Share-based Payment Arrangement, Expensed, Amount	Stock based compensation expense is included in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss as shown in the following table: Three Months Ended March 31, 2023 2022 Cost of revenues $ 11 $ 6 Research and development 9,346 3,632 Sales and marketing 779 348 General and administrative 10,937 10,600 Total $ 21,073 $ 14,586

ACCRUED EXPENSES AND OTHER CU_2

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)	3 Months Ended
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)	Mar. 31, 2023
Other Liabilities Disclosure [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following: March 31, December 31, 2022 Obligations under current leases $ 5,524 $ 4,903 Marketing related accruals 2,726 3,464 Sales and VAT tax accrual 2,421 2,396 Employee-related costs 1,938 4,233 Other 6,351 6,974 Total $ 18,960 $ 21,970

LOSS PER SHARE (Tables)

LOSS PER SHARE (Tables)	3 Months Ended
LOSS PER SHARE (Tables)	Mar. 31, 2023
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The diluted net loss per share attributable to common stockholders is calculated by giving effect to all potential dilutive common stock equivalents outstanding for the period. Three Months Ended March 31, (In thousands, except per share data) 2023 2022 Numerator: Net loss attributable to Class A and Class B common stockholders $ (2,582) $ (12,154) Denominator: Weighted-average shares in computing net loss per share attributable to Class A and Class B common stockholders, basic and diluted 40,618 38,590 Basic loss per common share $ (0.06) $ (0.31) Diluted loss per common share $ (0.06) $ (0.31)
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The potential shares of common stock that were excluded from the computation of diluted net loss per share attributable to common stockholders for the period presented because including them would have been antidilutive are as follows: Three Months Ended March 31, (in thousands) 2023 2022 Founder awards where performance has been met 180 180 Stock options outstanding (1) 3,865 5,435 RSUs outstanding (1) 2,048 756 Total 6,093 6,371 ________________ (1) Prior year amounts were adjusted in the current year table to include unvested options and RSUs.

DESCRIPTION OF THE BUSINESS A_2

DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION (Details)	Mar. 31, 2023 language
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of languages, more than	40

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 641,091	$ 608,180
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	48,462	91,189
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 592,629	$ 516,991

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Concentration Risk [Line Items]
Advertising costs	$ 11,093	$ 10,954
Accounts Receivable \| Customer Concentration Risk \| Apple
Concentration Risk [Line Items]
Concentration risk, percentage	66.90%		56.20%
Accounts Receivable \| Customer Concentration Risk \| Google
Concentration Risk [Line Items]
Concentration risk, percentage	19.30%		27.50%
Accounts Receivable \| Customer Concentration Risk \| Stripe
Concentration Risk [Line Items]
Concentration risk, percentage	10%
Revenue Benchmark \| Customer Concentration Risk \| Apple
Concentration Risk [Line Items]
Concentration risk, percentage	57.10%	51.10%
Revenue Benchmark \| Customer Concentration Risk \| Google
Concentration Risk [Line Items]
Concentration risk, percentage	26.20%	29.10%
Revenue Benchmark \| Customer Concentration Risk \| Stripe
Concentration Risk [Line Items]
Concentration risk, percentage	11.90%

REVENUE - Narrative (Details)

REVENUE - Narrative (Details)	Mar. 31, 2023 sourceOfRevenue user
Disaggregation of Revenue [Line Items]
Number of sources of revenue \| sourceOfRevenue	3
Number of users \| user	6
Number of hours to make certification decision	48 hours
Number of days to take exam	21 days
Expiration period to take exams	1 year
Minimum
Disaggregation of Revenue [Line Items]
Subscription period	6 months
Maximum
Disaggregation of Revenue [Line Items]
Subscription period	1 year

REVENUE - Disaggregation of Rev

REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 115,661	$ 81,220
Transferred over Time \| Subscription
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	86,185	58,010
Transferred over Time \| Advertising
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	11,635	11,748
Transferred over Time \| Duolingo English Test
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	9,972	8,080
Transferred over Time \| Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 7,869	$ 3,382

REVENUE - Deferred Revenue Roll

REVENUE - Deferred Revenue Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenue from Contract with Customer, Liability [Roll Forward]
Beginning balance	$ 157,550	$ 98,267
Amount from beginning balance recognized into revenue	(65,492)	(40,474)
Recognition of deferred revenue	(30,129)	(22,195)
Deferral of revenue	120,013	83,503
Ending balance	$ 181,942	$ 119,101

PROPERTY and EQUIPMENT, net - S

PROPERTY and EQUIPMENT, net - Summary (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 22,069	$ 21,187
Less: accumulated depreciation	(9,227)	(8,218)
Total property and equipment, net	12,842	12,969
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	16,693	15,983
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 5,376	$ 5,204

PROPERTY and EQUIPMENT, net -_2

PROPERTY and EQUIPMENT, net - Summary of Depreciation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Property, Plant and Equipment [Line Items]
Total	$ 1,009	$ 565
Research and development
Property, Plant and Equipment [Line Items]
Total	407	134
Sales and marketing
Property, Plant and Equipment [Line Items]
Total	48	19
General and administrative
Property, Plant and Equipment [Line Items]
Total	$ 554	$ 412

INTANGIBLE ASSETS AND GOODWIL_2

INTANGIBLE ASSETS AND GOODWILL - Capitalized Software (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets	$ 17,250	$ 16,827
Less: accumulated amortization	(8,775)	(8,330)
Intangible assets, net	$ 8,475	$ 8,497

INTANGIBLE ASSETS AND GOODWIL_3

INTANGIBLE ASSETS AND GOODWILL - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Other intangible assets	$ 18	$ 18
Capitalized software development costs	731		$ 1,131
Goodwill, tax deductible amount	3,915	3,983
Goodwill	$ 4,050	$ 4,050

INTANGIBLE ASSETS AND GOODWIL_4

INTANGIBLE ASSETS AND GOODWILL - Schedule of Capitalized Software Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Amortization of capitalized computer software	$ 753	$ 209
Cost of revenues
Finite-Lived Intangible Assets [Line Items]
Amortization of capitalized computer software	403	0
Sales and marketing
Finite-Lived Intangible Assets [Line Items]
Amortization of capitalized computer software	$ 350	$ 209

INCOME TAXES - Effective Income

INCOME TAXES - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Loss before (benefit) provision for income taxes	$ (2,698)	$ (12,126)
(Benefit) provision for income taxes	$ (116)	$ 28
Effective income tax rate	4.30%	(0.20%)

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narrative (Details) $ / shares in Units, shares in Thousands, $ in Thousands			1 Months Ended	3 Months Ended
	Jan. 01, 2023 shares	Jan. 01, 2022	Jun. 30, 2021 shares	Mar. 31, 2023 USD ($) tranche day $ / shares shares	Mar. 31, 2022 USD ($)	Jul. 26, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value, exercised				$ 55,062	$ 60,334
Unrecognized compensation cost, options				4,522
Unrecognized compensation cost				$ 167,895
Closing trading price, specified calendar \| day				60
Compensation expense				$ 21,073	14,586
Stock options outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, weighted-average period of recognition (in years)				1 year
Number of options available for grant (in shares) \| shares				10,011
RSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, weighted-average period of recognition (in years)				3 years
Unrecognized compensation expense, excluding options				$ 163,373
Equity instruments other than options, grants in period (in shares) \| shares				185
Performance Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, excluding options				$ 56,217
Performance Based RSUs \| Share-Based Payment Arrangement, Founders
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in usd per share) \| $ / shares				$ 61.56
Performance Based RSUs \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award service period				3 years 6 months 29 days
Performance Based RSUs \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award service period				5 years 11 months 1 day
Performance Based RSUs \| 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense				$ 7,140	$ 8,019
Performance Based RSUs \| Founders
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, excluding options				$ 110,817
Equity instruments other than options, grants in period (in shares) \| shares			1,800
Settlement period after vesting			1 year
Award vesting percentage			25%
Number of tranches \| tranche				10
Award service period			10 years
Performance Based RSUs \| Founders \| Tranche One and Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of tranches \| tranche				2
2021 Plan \| Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares) \| shares						7,946
Share-based compensation, shares outstanding increase, maximum amount (in percent)		5%
Additional shares authorized (in shares) \| shares	2,018
Employee Stock Purchase Plan \| Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (in shares) \| shares						1,119
Additional shares authorized (in shares) \| shares	319
2011 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)				4 years
Share-based compensation, term of award (in years)				10 years

STOCK-BASED COMPENSATION - Stoc

STOCK-BASED COMPENSATION - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Number of options
Options outstanding, beginning balance (in shares)	4,410
Granted (in shares)	0
Exercised (in shares)	(542)
Forfeited and expired (in shares)	(3)
Options outstanding, ending balance (in shares)	3,865	4,410
Number of options exercisable (in shares)	3,297
Weighted- average exercise price
Outstanding, beginning balance (in usd per share)	$ 14.04
Granted (in usd per share)
Exercised (in usd per share)	8.57
Forfeited and expired (in usd per share)	22.37
Outstanding, ending balance (in usd per share)	14.80	$ 14.04
Weighted average exercise price, options exercisable (in usd per share)	$ 14.05
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term (in years), outstanding	6 years 2 months 1 day	6 years 3 months
Weighted average remaining contractual term (in years), exercisable	6 years
Aggregate intrinsic value, outstanding	$ 493,610	$ 251,832
Aggregate intrinsic value, exercisable	$ 423,829

STOCK-BASED COMPENSATION - Sche

STOCK-BASED COMPENSATION - Schedule of Restricted Stock Unit Activity (Details) - RSUs outstanding - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Restricted stock units
Beginning balance (in shares)	2,048	2,036
Granted (in shares)	185
Released (in shares)	(115)
Forfeited (in shares)	(58)
Ending balance (in shares)	2,048
Weighted- average grant date fair value per share
Beginning balance (in usd per share)	$ 85.74
Granted (in usd per share)	97.62
Released (in usd per share)	84.18
Forfeited (in usd per share)	97.80
Ending balance (in usd per share)	$ 86.56

STOCK-BASED COMPENSATION - Sc_2

STOCK-BASED COMPENSATION - Schedule of Payment Award (Details) - RSUs outstanding shares in Thousands	Mar. 31, 2023 $ / shares shares
1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 127.50
Number of RSUs Eligible to Vest (in shares) \| shares	90
2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 153
Number of RSUs Eligible to Vest (in shares) \| shares	90
3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 178.50
Number of RSUs Eligible to Vest (in shares) \| shares	90
4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 204
Number of RSUs Eligible to Vest (in shares) \| shares	180
5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 255
Number of RSUs Eligible to Vest (in shares) \| shares	180
6
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 306
Number of RSUs Eligible to Vest (in shares) \| shares	180
7
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 357
Number of RSUs Eligible to Vest (in shares) \| shares	180
8
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 408
Number of RSUs Eligible to Vest (in shares) \| shares	180
9
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 612
Number of RSUs Eligible to Vest (in shares) \| shares	270
10
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company Stock Price Hurdle (in usd per share) \| $ / shares	$ 816
Number of RSUs Eligible to Vest (in shares) \| shares	360

STOCK-BASED COMPENSATION - Sc_3

STOCK-BASED COMPENSATION - Schedule of Income Statement Location for Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 21,073	$ 14,586
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	11	6
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	9,346	3,632
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	779	348
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 10,937	$ 10,600

ACCRUED EXPENSES AND OTHER CU_3

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Other Liabilities Disclosure [Abstract]
Obligations under current leases	$ 5,524	$ 4,903
Marketing related accruals	2,726	3,464
Sales and VAT tax accrual	2,421	2,396
Employee-related costs	1,938	4,233
Other	6,351	6,974
Total	$ 18,960	$ 21,970

EMPLOYEE BENEFIT PLAN (Details)

EMPLOYEE BENEFIT PLAN (Details) - USD ($)	3 Months Ended
EMPLOYEE BENEFIT PLAN (Details) - USD ($)	Mar. 31, 2023	Mar. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, contributions by employer	$ 1,397,000	$ 983,000
Defined contribution plan, employer discretionary contribution amount	$ 0	$ 0
First 4% of Employee Elective Deferral
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percent of match (in percent)	100%
Employer matching contribution, percent of employees' gross pay (in percent)	4%
Next 2% of Employee Elective Deferral
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percent of match (in percent)	50%
Employer matching contribution, percent of employees' gross pay (in percent)	2%

LOSS PER SHARE - Schedule of Ea

LOSS PER SHARE - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Numerator:
Net loss attributable to Class A and Class B common stockholders	$ (2,582)	$ (12,154)
Denominator:
Weighted-average shares in computing net loss per share attributable to Class A and Class B common stockholders, basic (in shares)	40,618	38,590
Weighted-average shares in computing net loss per share attributable to Class A and Class B common stockholders, diluted (in shares)	40,618	38,590
Basic loss per common share (in usd per share)	$ (0.06)	$ (0.31)
Diluted loss per common share (in usd per share)	$ (0.06)	$ (0.31)

LOSS PER SHARE - Narrative (Det

LOSS PER SHARE - Narrative (Details) shares in Thousands	3 Months Ended
LOSS PER SHARE - Narrative (Details) shares in Thousands	Mar. 31, 2023 votePerShare shares	Mar. 31, 2022 shares
Performance Based RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Founder awards where performance not met (in shares) \| shares	1,620	1,620
Common Class A
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Voting rights, per share	1
Common Class B
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Voting rights, per share	20

LOSS PER SHARE - Schedule of An

LOSS PER SHARE - Schedule of Antidilutive Securities (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of earnings per share (in shares)	6,093	6,371
Founder awards where performance has been met
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of earnings per share (in shares)	180	180
Stock options outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of earnings per share (in shares)	3,865	5,435
RSUs outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of earnings per share (in shares)	2,048	756