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Operating lease assets obtained in exchange for operating lease liabilities including adjustments Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Underlying Security Market Price Change Underlying Security Market Price Change, Percent Tax Credit Carryforward, Name [Domain] Tax Credit Carryforward, Name [Domain] Individual: Individual [Axis] Annual increase percentage of shares reserved for issuance Annual Increase Percentage Of Shares Reserved For Issuance Annual increase percentage of shares reserved for issuance. 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Statement [Line Items] Statement [Line Items] Increase (decrease) in the additional-paid-in-capital of Viant Technology Inc. resulting from ownership changes in Viant Technology LLC Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Ownership Changes Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Ownership Changes Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Contractual Obligation, to be Paid, Year Two Contractual Obligation, to be Paid, Year Two Schedule of Major Classes of Property, Equipment and Software Property, Plant and Equipment [Table Text Block] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Consideration transferred Business Combination, Consideration Transferred Weighted-average grant-date fair value, beginning balance (dollars per share) Weighted-average grant-date fair value, ending balance (dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Liabilities and stockholders' equity Liabilities and Equity [Abstract] Weighted average exercise price, vested and exercisable (dollars per share) Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Exercisable Weighted Average Exercise Price Share based compensation arrangement by share based payment award options vested and exercisable weighted average exercise price. Changes in valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Minimum Minimum [Member] Restatement Determination Date Restatement Determination Date Adoption Date Trading Arrangement Adoption Date Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Related Party Transactions [Abstract] Related Party Transactions [Abstract] Advertising Agency Risk Advertising Agency Risk [Member] Advertising agency risk. Schedule Of Property Plant And Equipment [Table] Property, Plant and Equipment [Table] Weighted-Average Exercise Price of Options outstanding, beginning balance (dollars per share) Weighted-Average Exercise Price of Options outstanding, ending balance (dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price Operating lease assets, net Operating Lease, Right-of-Use Asset Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Beginning balance (shares) Ending balance (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Provision for doubtful accounts Accounts Receivable, Credit Loss Expense (Reversal) Segments [Axis] Segments [Axis] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Exchange units for shares of common stock Exchange Units For Shares Of Common Stock Exchange units for shares of common stock. 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Entity File Number Entity File Number Revenue Revenue from Contract with Customer [Text Block] Document Fiscal Year Focus Document Fiscal Year Focus Noncontrolling Interests Noncontrolling Interest [Member] Income Statement [Abstract] Income Statement [Abstract] Entity Address, Address Line One Entity Address, Address Line One U.S. federal income tax Current Federal Tax Expense (Benefit) Repurchase of stock related to tax withholdings on vested equity awards Treasury Stock, Value, Acquired, Cost Method Entity Address, Address Line Two Entity Address, Address Line Two Debt Instrument, Name Debt Instrument, Name [Domain] Other accrued liabilities Other Accrued Liabilities, Current Name Forgone Recovery, Individual Name Foreign Income (Loss) from Continuing Operations before Income Taxes, Foreign Operating lease weighted average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Add back: Reallocation of net income attributable to noncontrolling interest from the assumed exchange of RSUs and NQSOs for Class A common stock Dilutive Securities, Effect on Basic Earnings Per Share, ESOP Convertible Preferred Stock, Net Dilutive Securities, Effect on Basic Earnings Per Share, ESOP Convertible Preferred Stock, Net 2030 Finite-Lived Intangible Asset, Expected Amortization, Year Five Document Period End Date Document Period End Date Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Accrued traffic acquisition costs Accrued Traffic Acquisition Costs Accrued traffic acquisition costs. 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Meals and entertainment Effective Income Tax Rate Reconciliation, Nondeductible Expense, Meals and Entertainment, Amount Timing of Transfer of Good or Service Timing of Transfer of Good or Service [Domain] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Dilutive Securities, Effect on Basic Earnings Per Share, ESOP Convertible Preferred Stock, Income Tax Effect Dilutive Securities, Effect on Basic Earnings Per Share, ESOP Convertible Preferred Stock, Income Tax Effect Dilutive Securities, Effect on Basic Earnings Per Share, ESOP Convertible Preferred Stock, Income Tax Effect Retirement of treasury stock Treasury Stock, Retired, Cost Method, Amount North Carolina NORTH CAROLINA Deferred Tax Asset, Valuation Allowance [Table] Deferred Tax Asset, Valuation Allowance [Table] 2028 Lessee, Operating Lease, Liability, to be Paid, Year Three PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Purchases from related parties Related Party Transaction, Purchases from Related Party State Income Tax Paid, State and Local, after Refund Received TRA Deferred Tax Assets, Tax Receivable Agreement Deferred Tax Assets, Tax Receivable Agreement Adjustment to Compensation: Adjustment to Compensation [Axis] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Accounts Receivable Accounts Receivable [Member] Less: Net income (loss) attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Document Transition Report Document Transition Report Other Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent Schedule of Unrecognized Tax Benefits Roll Forward Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent Customer Customer [Domain] Entity Current Reporting Status Entity Current Reporting Status Accumulated Deficit Retained Earnings [Member] Ownership percentage by Viant Technology Inc. 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