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DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION (Details) $ / shares in Units, shares in Thousands, $ in Thousands |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Jul. 30, 2021 USD ($) $ / shares shares | Dec. 31, 2023 USD ($) language shares | Dec. 31, 2022 USD ($) shares | Dec. 31, 2021 USD ($) | Jul. 29, 2021 USD ($) shares | Jul. 15, 2021 shares | Dec. 31, 2020 USD ($)
Business And Organization [Line Items] |  |  |  |  |  |  |
Issuance of common stock in connection with the initial public offering, net of underwriting discounts and issuance costs | $ | $ 455,532 | $ 0 | $ 0 | $ 426,191 |  |  |
Authorized (in shares) |  |  |  |  | 19,074 |  |
Carrying value of convertible preferred stock | $ |  |  |  | $ 0 | $ 182,609 |  | $ 182,609
Number of languages, more than | language |  | 40 |  |  |  |  |
Common Class A |  |  |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |  |  |
Common stock, shares outstanding (in shares) |  | 36,311 | 31,899 |  |  |  |
Common Class A | IPO |  |  |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |  |  |
Sale of stock, number of shares issued in transaction (in shares) | 5,872 |  |  |  |  |  |
Sale of stock, price per share (in usd per share) | $ / shares | $ 102.00 |  |  |  |  |  |
Common Class A | IPO | Stockholders |  |  |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |  |  |
Sale of stock, number of shares issued in transaction (in shares) | 1,406 |  |  |  |  |  |
Common Class A | IPO | Duolingo |  |  |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |  |  |
Sale of stock, number of shares issued in transaction (in shares) | 4,466 |  |  |  |  |  |
Common Class A | Over-Allotment Option |  |  |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |  |  |
Sale of stock, number of shares issued in transaction (in shares) | 766 |  |  |  |  |  |
Common Class B |  |  |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |  |  |
Conversion ratio |  |  |  |  | 1 |  |
Common stock, shares outstanding (in shares) |  | 6,215 | 8,462 |  |  |  |
Common Class B | Founders |  |  |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |  |  |
Common stock, shares outstanding (in shares) |  |  |  |  |  | 6,930 |

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