Nature of Operations - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		6 Months Ended
	Feb. 12, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Nature Of Operations [Line Items]
Preferred stock, shares authorized	10,000,000	10,000,000		10,000,000
Proceeds from issuance of common stock, net of underwriting discounts			$ 232,500
Common stock, voting rights		The Class B stockholders and Class A stockholders initially had 80.5% and 19.5%, respectively, of the combined voting power of the Company’s common stock. The Class A common stock outstanding represents 100% of the rights of the holders of all classes of the Company’s outstanding common stock to share in distributions from the Company, except for the right of Class B stockholders to receive the par value of the Class B common stock upon our liquidation, dissolution or winding up or an exchange of Class B units
Underwriters
Nature Of Operations [Line Items]
Common stock shares issued and sold	10,000,000
Sale of stock, price per share	$ 25.00
Proceeds from issuance of common stock, net of underwriting discounts	$ 250,000
Payments of stock issuance costs	$ 17,500
Class A Common Stock
Nature Of Operations [Line Items]
Common stock, shares authorized	450,000,000	450,000,000		450,000,000
Common stock shares issued to continuing members		24,870
Underwrites options exercised shares issued	1,500,000
Common stock voting rights percentage	19.50%
Percentage of voting rights of outstanding common stock	100.00%
Class B Common Stock
Nature Of Operations [Line Items]
Common stock, shares authorized	150,000,000	150,000,000		150,000,000
Common stock shares issued to continuing members		(24,870)
Common stock voting rights percentage	80.50%
Class B Common Stock | Viant Technology LLC
Nature Of Operations [Line Items]
Common stock shares issued for each membership unit	1
Common stock shares issued to continuing members	48,935,559
Continuing Members Class B Units | Viant Technology LLC
Nature Of Operations [Line Items]
Continuing members units exchange description		one-for-one basis
Continuing members, membership units	48,935,559
Class A Units
Nature Of Operations [Line Items]
Members equity units received in exchange of units	1,500,000
Class A Units | Viant Technology LLC
Nature Of Operations [Line Items]
Payments to acquire units	$ 232,500
Member units acquired, units	10,000,000