Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Mar. 25, 2025	Jun. 30, 2024
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2024
Document Transition Report	false
Current Fiscal Year End Date	--12-31
Entity File Number	001-41261
Entity Registrant Name	DIRECT DIGITAL HOLDINGS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	87-2306185
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
Title of 12(b) Security	Class A Common Stock, par value $0.001 per share
Trading Symbol	DRCT
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	true
Document Financial Statement Restatement Recovery Analysis [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 12.8
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Entity Central Index Key	0001880613
Common Class A
Entity Common Stock, Shares Outstanding		6,913,999
Common Class B
Entity Common Stock, Shares Outstanding		10,868,000