| Cover | Oct. 18, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 18, 2024 |
| Entity File Number | 001-41261 |
| Entity Registrant Name | Direct Digital Holdings, Inc. |
| Entity Central Index Key | 0001880613 |
| Entity Tax Identification Number | 87-2306185 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 1177 West Loop South |
| Entity Address, Address Line Two | Suite 1310 |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77027 |
| City Area Code | 832 |
| Local Phone Number | 402-1051 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A common stock, par value $0.001 per share |
| Trading Symbol | DRCT |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
