Stockholders' equity - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2025	Dec. 31, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares of common stock reserved (in shares)	35,869,967	30,710,794
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding (in shares)	957,359	1,401,086
RSU outstanding and PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding and PSUs (in shares)	18,926,577	15,809,202
2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options available for future issuance (in shares)	11,952,297	10,514,374
2021 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options available for future issuance (in shares)	4,033,734	2,986,132

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

Udemy, Inc. 10-Q