| Document and Entity Information | Aug. 09, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 09, 2022 |
| Entity Registrant Name | Viant Technology Inc. |
| Entity Central Index Key | 0001828791 |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity File Number | 001-40015 |
| Entity Incorporation State Country Code | DE |
| Entity Tax Identification Number | 85-3447553 |
| 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) |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Class A common stock, par value $0.001 per share |
| Trading Symbol | DSP |
| Security Exchange Name | NASDAQ |
