Stockholders' (Deficit) Equity and Stock-Based Compensation - IPO (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended			12 Months Ended
	Jul. 28, 2022	Feb. 15, 2022	Dec. 31, 2023	Nov. 30, 2023	Aug. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Oct. 30, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Subsidiary, Sale of Stock [Line Items]
Preferred stock authorized (in shares)			10,000,000			10,000,000
Preferred stock par value (in dollar per share)			$ 0.001			$ 0.001
Remainder of the principal and interest paid for the common units redemption	$ 4.0
Class of warrant or right exercised						2,200
Warrants outstanding							3,220,000
Warrants purchased								1,004,148
Initial public offering
Subsidiary, Sale of Stock [Line Items]
Units issued in IPO		2,800,000
Number of shares of common stock		1
Number of warrants to purchase each share		1
Warrants exercise price		$ 5.50
Warrants exercisable term		5 years
Warrants outstanding			0			0
Net proceeds from the offering		$ 10.2
Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Option to purchase additional units		140,000
Class of warrant or right exercised				10,500
Warrants outstanding			10,500			10,500
Term of underwriters		45 days
Exercise price of additional units		$ 6.60
Public offering price per unit sold		120.00%
Number of units exercised				70,000
Units outstanding			70,000			70,000
Over-Allotment Option | Maximum
Subsidiary, Sale of Stock [Line Items]
Warrants purchased		420,000
Common Class A
Subsidiary, Sale of Stock [Line Items]
Common Stock, Authorized			160,000,000			160,000,000	160,000,000		160,000,000	160,000,000	160,000,000
Common Stock, par value			$ 0.001			$ 0.001	$ 0.001		$ 0.001	$ 0.001	$ 0.001
Common Class A | Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Option to purchase warrants		21,000
Warrants exercise price		$ 0.012
Warrants outstanding			0			0
Warrants purchased		420,000
Public offering price per warrant sold		120.00%
Common Class B
Subsidiary, Sale of Stock [Line Items]
Common Stock, Authorized			20,000,000			20,000,000	20,000,000		20,000,000	20,000,000	20,000,000
Common Stock, par value			$ 0.001			$ 0.001	$ 0.001		$ 0.001	$ 0.001	$ 0.001
Direct Digital Management LLC | Common Class A
Subsidiary, Sale of Stock [Line Items]
Common Units Exchanged			410,000		100,000	410,000	100,000
Number of shares of common stock			1			1
Direct Digital Management LLC | Common Class B
Subsidiary, Sale of Stock [Line Items]
Number of shares of common stock			10,868,000			10,868,000
DDH LLC
Subsidiary, Sale of Stock [Line Items]
Noneconomic voting rights (as a percent)						100.00%
DDH LLC | Initial public offering | Related Party | Woolford
Subsidiary, Sale of Stock [Line Items]
Aggregate purchase price of units issued		$ 14.2
Purchase price paid		$ 10.3
DDH LLC | Initial public offering | Common Units | Related Party | Woolford
Subsidiary, Sale of Stock [Line Items]
Remaining number of units purchased		5,637
DDH LLC | Initial public offering | Class B Preferred Units. | Related Party | Woolford
Subsidiary, Sale of Stock [Line Items]
Remaining number of units purchased		7,046