Noncontrolling Interests - Summary of Effect of Changes in Ownership Interest in Viant Technology LLC on Equity (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Noncontrolling Interest [Abstract]
Net loss attributable to Viant Technology Inc.	$ (3,192)	$ (3,104)
Transfers to noncontrolling interests:
Decrease in the additional-paid-in-capital of Viant Technology Inc. as a result in ownership changes in Viant Technology LLC	(4,276)
Net decrease in equity of Viant Technology Inc. due to equity interest transactions with noncontrolling interests	$ (7,468)

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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