CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Revenue	$ 197,168	$ 224,127	$ 165,251
Operating expenses:
Platform operations	116,725	129,604	88,260
Sales and marketing	63,957	65,042	28,887
Technology and development	21,294	25,372	8,698
General and administrative	44,452	46,904	17,639
Total operating expenses	246,428	266,922	143,484
Income (loss) from operations	(49,260)	(42,795)	21,767
Interest expense (income), net	(1,481)	864	1,038
Other expense	310	60	91
Gain on extinguishment of debt	0	(6,110)	0
Total other expense (income), net	(1,171)	(5,186)	1,129
Net income (loss)	(48,089)	(37,609)	20,638
Less: Net loss attributable to noncontrolling interests	(36,176)	(29,867)	$ 0
Net loss attributable to Viant Technology Inc.	$ (11,913)	$ (7,742)
Earnings (loss) per Class A common stock/unit:
Basic (dollars per share)	$ (0.84)	$ (0.63)	$ 20.64
Diluted (dollars per share)	$ (0.84)	$ (0.63)	$ 20.64
Weighted-average Class A common stock/units outstanding:
Basic (shares)	14,185,000	12,364,000	400,000
Diluted (shares)	14,185,000	12,364,000	1,000,000