SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
Sep. 30, 2024
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 U.S. (“GAAP”) from the Company’s accounting records and reflect the consolidated financial position and results of operations for the three and nine months ended September 30, 2024 and 2023. Unless otherwise specified, all dollar amounts (other than per share 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 and intangible assets, 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, contingent liabilities, fair value of investments and valuation of goodwill and intangible assets from acquisitions. 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 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.
Investments	Investments —Investments consist primarily of corporate debt securities and U.S. Treasury securities. Management determines the appropriate classification of investments at the time of purchase based upon management’s intent with regard to such investments. The Company’s investments are classified as held-to-maturity at the time of purchase, and such classifications are reevaluated as of each balance sheet date. All highly liquid investments with an original maturity of 90 days or less when purchased are considered to be cash equivalents. Investments with remaining contractual maturities of one year or less from the balance sheet date, which are not considered cash equivalents, are classified as short-term investments, and those with remaining contractual maturities greater than one year from the balance sheet date are classified as long-term investments. All investments are recorded at amortized cost. Realized gains and losses on sales and maturities of investments are determined based on the specific identification method and are recognized in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Income. We perform periodic evaluations to determine whether any declines in the fair value of investments below cost are other-than-temporary. The evaluation consists of qualitative and quantitative factors regarding the severity and duration of the unrealized loss, as well as the Company’s ability and intent to hold the investments until a forecasted recovery occurs. The impairments are considered to be other-than-temporary if they are related to deterioration in credit risk or if it is likely that the underlying securities will be sold or mature prior to a full recovery of their cost basis. Other-than-temporary fair value impairments, if any, are determined based on the specific identification method and are reported in Other income (expense), net in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Income
Acquisitions	Acquisitions—The Company uses the acquisition method of accounting for business combination transactions, and, accordingly, recognizes the fair values of assets acquired and liabilities assumed in the Company’s Unaudited Condensed Consolidated Financial Statements. The excess of the fair value of purchase consideration over the values of these identifiable assets and liabilities is recorded as goodwill. Transaction costs related to the acquisition of the acquired company are expensed as incurred. The allocation of fair values may be subject to adjustment after the initial allocation for up to a one-year period as more information becomes available relative to the fair values as of the acquisition date. The Unaudited Condensed Consolidated Financial Statements include the results of operations of any acquired company since the acquisition date.
Advertising Costs	Advertising Costs— Advertising costs were approximately $18,149 and $45,617 for the three and nine months ended September 30, 2024, and $16,229 and $39,528 for the three and nine months ended September 30, 2023, respectively, and are included within Sales and marketing in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Income.
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. 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.
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.
Allowance for Credit Losses	Allowance for Credit Losses—The Company evaluates its cash equivalents, accounts receivable and held-to-maturity marketable securities financial assets for expected credit losses. Expected credit losses represent the portion of the amortized cost basis of a financial asset that an entity does not expect to collect. An allowance for expected credit losses is meant to reflect a risk of loss even if remote, irrespective of the expectation of collection from a particular issuer or debt security. The Company has not historically experienced any credit losses on any of its financial assets. With respect to cash equivalents and accounts receivable, given consideration of their short maturity, lack of historical losses and the current environment, the Company concluded there is generally no expected credit losses for these financial assets. With respect to held-to-maturity marketable securities which are comprised of debt securities, the Company evaluates expected credit losses on a pooled basis based on issuer-type which have similar credit risk characteristics. The allowance for credit losses is immaterial for all periods presented.
Recently Issued Pronouncements Not Yet Adopted and Recently Adopted Accounting Pronouncements	Recently Issued Pronouncements Not Yet Adopted In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2023-07, Segment Reporting (Topic 280), which improves reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. The standard is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company does not expect the adoption of the new guidance will have a material impact on the Company’s consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740), which includes improvements to income tax disclosures. The standard is effective for public entities in fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company does not expect the adoption of the new guidance will have a material impact on the Company’s consolidated financial statements and related disclosures. Recently Adopted Accounting Pronouncements There are no recently adopted accounting pronouncements.
Fair Value	The Company accounts for certain assets and liabilities at fair value in accordance with the accounting guidance applicable to fair value measurements and disclosures. The carrying values of cash, cash equivalents, accounts receivable, accounts payable, and accrued expenses are deemed to be reasonable estimates of their fair values because of their short-term nature. The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring and non-recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities, which are required to be recorded at fair value, the Company considers the principal or most advantageous market in which the Company would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as inherent risk, transfer restrictions, and credit risk. The Company applies the following fair value hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1—Observable inputs such as quoted prices in active markets for identical investments that the Company has the ability to access. Level 2—Inputs include: •Quoted prices for similar assets or liabilities in active markets; •Quoted prices for identical or similar assets or liabilities in inactive markets; •Inputs, other than quoted prices in active markets, which are observable either directly or indirectly; •Inputs that are derived principally from, or corroborated by, observable market data by correlation or other means. Level 3—Unobservable inputs in which there is little or no market activity for the asset or liability, which require the reporting entity to develop its own estimates and assumptions relating to the pricing of the asset or liability including assumptions regarding risk.
Revenue	REVENUE The Company has four predominant sources of revenues; time-based subscriptions, in-app advertising placement by third parties, the Duolingo English Test, and In-App Purchases. 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 Duolingo and its 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 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 Duolingo’s 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 received 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 streams, which most closely depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

9 Months Ended

Sep. 30, 2024

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 U.S. (“GAAP”) from the Company’s accounting records and reflect the consolidated financial position and results of operations for the three and nine months ended September 30, 2024 and 2023. Unless otherwise specified, all dollar amounts (other than per share 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 and intangible assets, 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, contingent liabilities, fair value of investments and valuation of goodwill and intangible assets from acquisitions. 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 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.

Investments

Investments —Investments consist primarily of corporate debt securities and U.S. Treasury securities. Management determines the appropriate classification of investments at the time of purchase based upon management’s intent with regard to such investments. The Company’s investments are classified as held-to-maturity at the time of purchase, and such classifications are reevaluated as of each balance sheet date. All highly liquid investments with an original maturity of 90 days or less when purchased are considered to be cash equivalents. Investments with remaining contractual maturities of one year or less from the balance sheet date, which are not considered cash equivalents, are classified as short-term investments, and those with remaining contractual maturities greater than one year from the balance sheet date are classified as long-term investments. All investments are recorded at amortized cost. Realized gains and losses on sales and maturities of investments are determined based on the specific identification method and are recognized in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Income.

We perform periodic evaluations to determine whether any declines in the fair value of investments below cost are other-than-temporary. The evaluation consists of qualitative and quantitative factors regarding the severity and duration of the unrealized loss, as well as the Company’s ability and intent to hold the investments until a forecasted recovery occurs. The impairments are considered to be other-than-temporary if they are related to deterioration in credit risk or if it is likely that the underlying securities will be sold or mature prior to a full recovery of their cost basis. Other-than-temporary fair value impairments, if any, are determined based on the specific identification method and are reported in Other income (expense), net in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Income

Acquisitions

Acquisitions—The Company uses the acquisition method of accounting for business combination transactions, and, accordingly, recognizes the fair values of assets acquired and liabilities assumed in the Company’s Unaudited Condensed Consolidated Financial Statements. The excess of the fair value of purchase consideration over the values of these identifiable assets and liabilities is recorded as goodwill. Transaction costs related to the acquisition of the acquired company are expensed as incurred. The allocation of fair values may be subject to adjustment after the initial allocation for up to a one-year period as more information becomes available relative to the fair values as of the acquisition date. The Unaudited Condensed Consolidated Financial Statements include the results of operations of any acquired company since the acquisition date.

Advertising Costs

Advertising Costs— Advertising costs were approximately $18,149 and $45,617 for the three and nine months ended September 30, 2024, and $16,229 and $39,528 for the three and nine months ended September 30, 2023, respectively, and are included within Sales and marketing in the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Income.

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.

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.

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.

Allowance for Credit Losses

Allowance for Credit Losses—The Company evaluates its cash equivalents, accounts receivable and held-to-maturity marketable securities financial assets for expected credit losses. Expected credit losses represent the portion of the amortized cost basis of a financial asset that an entity does not expect to collect. An allowance for expected credit losses is meant to reflect a risk of loss even if remote, irrespective of the expectation of collection from a particular issuer or debt security. The Company has not historically experienced any credit losses on any of its financial assets.

With respect to cash equivalents and accounts receivable, given consideration of their short maturity, lack of historical losses and the current environment, the Company concluded there is generally no expected credit losses for these financial assets. With respect to held-to-maturity marketable securities which are comprised of debt securities, the Company evaluates expected credit losses on a pooled basis based on issuer-type which have similar credit risk characteristics. The allowance for credit losses is immaterial for all periods presented.

Recently Issued Pronouncements Not Yet Adopted and Recently Adopted Accounting Pronouncements

Recently Issued Pronouncements Not Yet Adopted

In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2023-07, Segment Reporting (Topic 280), which improves reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. The standard is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company does not expect the adoption of the new guidance will have a material impact on the Company’s consolidated financial statements and related disclosures.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740), which includes improvements to income tax disclosures. The standard is effective for public entities in fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company does not expect the

adoption of the new guidance will have a material impact on the Company’s consolidated financial statements and related disclosures.

Recently Adopted Accounting Pronouncements

There are no recently adopted accounting pronouncements.

Fair Value

The Company accounts for certain assets and liabilities at fair value in accordance with the accounting guidance applicable to fair value measurements and disclosures. The carrying values of cash, cash equivalents, accounts receivable, accounts payable, and accrued expenses are deemed to be reasonable estimates of their fair values because of their short-term nature.

The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring and non-recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities, which are required to be recorded at fair value, the Company considers the principal or most advantageous market in which the Company would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as inherent risk, transfer restrictions, and credit risk.

The Company applies the following fair value hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement:

Level 1—Observable inputs such as quoted prices in active markets for identical investments that the Company has the ability to access.

Level 2—Inputs include:

•Quoted prices for similar assets or liabilities in active markets;

•Quoted prices for identical or similar assets or liabilities in inactive markets;

•Inputs, other than quoted prices in active markets, which are observable either directly or indirectly;

•Inputs that are derived principally from, or corroborated by, observable market data by correlation or other means.

Level 3—Unobservable inputs in which there is little or no market activity for the asset or liability, which require the reporting entity to develop its own estimates and assumptions relating to the pricing of the asset or liability including assumptions regarding risk.

Revenue

REVENUE

The Company has four predominant sources of revenues; time-based subscriptions, in-app advertising placement by third parties, the Duolingo English Test, and In-App Purchases. 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 Duolingo and its 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 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 Duolingo’s 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 received 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 streams, which most closely depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors.