Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2022	Aug. 05, 2022
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2022
Document Transition Report	false
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2022
Current Fiscal Year End Date	--12-31
Entity Registrant Name	Viant Technology Inc.
Entity Central Index Key	0001828791
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-3447553
Entity File Number	001-40015
Entity Address, Address Line One	2722 Michelson Drive
Entity Address, Address Line Two	Suite 100
Entity Address, City or Town	Irvine
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92612
Local Phone Number	861-8888
City Area Code	949
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Ex Transition Period	false
Entity Shell Company	false
Title of 12(b) Security	Class A common stock, par value $0.001 per share
Trading Symbol	DSP
Name of each exchange on which registered	NASDAQ
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		14,253,800
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		47,082,260