SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
Mar. 31, 2025
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 months ended March 31, 2025 and 2024. 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, valuation of deferred tax assets and liabilities, stock-based compensation, operating lease right-of-use assets and liabilities, capitalization of internally developed software and associated useful lives, contingent liabilities, 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.
Advertising Costs	Advertising Costs— Advertising costs were approximately $17,535 and $14,020 for the three months ended March 31, 2025 and 2024, 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 deposits and certificates of deposit with banks which exceed the Federal Deposit Insurance Corporation (“FDIC”) insured limit and money market accounts which are not FDIC insured. 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.
Segment	Segment—The Company operates as a single operating segment and derives revenues from customers through time-based subscriptions, in-app advertising placement by third parties, the Duolingo English Test, and In-App Purchases. The Chief Executive Officer, as the chief operating decision maker, evaluates the Company’s performance and allocates resources based on consolidated net income, as presented in the income statement, supplemented by disaggregated revenue details. Significant segment expenses are those that are presented on the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Income. The measure of segment assets is reported on the balance sheet as total consolidated assets. Accordingly, the Company has determined that it has a single reportable segment and operating segment structure, and operates as one reporting unit.
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. There is no allowance for credit losses for all periods presented.
Recently Issued Pronouncements Not Yet Adopted and Recently Adopted Accounting Pronouncements	Recently Issued Pronouncements Not Yet Adopted In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“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. In November 2024, the FASB issued ASU 2024-03, Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses. The amendment requires new financial statement disclosures to provide disaggregated information for certain types of expenses, including employee compensation, depreciation, and amortization in commonly presented expense captions such as cost of revenue, sales and marketing, and general and administrative expenses. The amendments in this ASU are effective for annual reporting periods beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. The Company is in the process of evaluating the effect that the adoption of these standards will have on its consolidated financial statements. 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 identical or 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	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)

3 Months Ended

Mar. 31, 2025

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 months ended March 31, 2025 and 2024. 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, valuation of deferred tax assets and liabilities, stock-based compensation, operating lease right-of-use assets and liabilities, capitalization of internally developed software and associated useful lives, contingent liabilities, 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.

Advertising Costs

Advertising Costs— Advertising costs were approximately $17,535 and $14,020 for the three months ended March 31, 2025 and 2024, 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 deposits and certificates of deposit with banks which exceed the Federal Deposit Insurance Corporation (“FDIC”) insured limit and money market accounts which are not FDIC insured. 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.

Segment

Segment—The Company operates as a single operating segment and derives revenues from customers through time-based subscriptions, in-app advertising placement by third parties, the Duolingo English Test, and In-App Purchases. The Chief Executive Officer, as the chief operating decision maker, evaluates the Company’s performance and allocates resources based on consolidated net income, as presented in the income statement, supplemented by disaggregated revenue details. Significant segment expenses are those that are presented on the Unaudited Condensed Consolidated Statements of Operations and Comprehensive Income. The measure of segment assets is reported on the balance sheet as total consolidated assets. Accordingly, the Company has determined that it has a single reportable segment and operating segment structure, and operates as one reporting unit.

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. There is no allowance for credit losses for all periods presented.

Recently Issued Pronouncements Not Yet Adopted and Recently Adopted Accounting Pronouncements

Recently Issued Pronouncements Not Yet Adopted

In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“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.

In November 2024, the FASB issued ASU 2024-03, Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses. The amendment requires new financial statement disclosures to provide disaggregated information for certain types of expenses, including employee compensation, depreciation, and amortization in commonly presented expense captions such as cost of revenue, sales and marketing, and general and administrative expenses. The amendments in this ASU are effective for annual reporting periods beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. The Company is in the process of evaluating the effect that the adoption of these standards will have on its consolidated financial statements.

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 identical or 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

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.