| Cover | May 20, 2022 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 20, 2022 |
| Entity File Number | 001-41261 |
| Entity Registrant Name | Direct Digital Holdings, Inc. |
| Entity Central Index Key | 0001880613 |
| Entity Tax Identification Number | 83-0662116 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 1233 West Loop South |
| Entity Address, Address Line Two | Suite 1170 |
| 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 |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
| Class A common stock, par value $0.001 per share | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Class A common stock, par value $0.001 per share |
| Trading Symbol | DRCT |
| Security Exchange Name | NASDAQ |
| Warrants to purchase Class A common stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants to purchase Class A common stock |
| Trading Symbol | DRCTW |
| Security Exchange Name | NASDAQ |
