Domestic Rate Loans Fed Funds Effective Rate Overnight Index Swap Rate [Member] Adjustments to reconcile income (loss) to net cash provided by (used in) operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Goodwill Goodwill, Acquired During Period Statistical Measurement Statistical Measurement [Domain] Related Parties Related Party Transactions Disclosure [Text Block] Principal Forgiveness Principal Forgiveness [Member] Components of Lease Expense Lease, Cost [Table Text Block] Summary of Future Minimum Payments Under Non-Cancelable Operating Leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Cover [Abstract] Cover [Abstract] Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Five Net increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Nature Of Operations [Table] Nature Of Operations [Table] Nature of Operations. Loan Restructuring Modification Loan Restructuring Modification [Axis] Future Minimum Payments Under Non-cancelable Operating Leases Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Other current liabilities Other Liabilities, Current Income Tax Jurisdiction Income Tax Jurisdiction [Domain] Deferred offering costs capitalized Deferred Offering Costs Trading Symbol Trading Symbol Percentage of voting rights of outstanding common stock Percentage Of Voting Rights Of Outstanding Common Stock Percentage of voting rights of outstanding common stock. All Trading Arrangements All Trading Arrangements [Member] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Non-NEOs Non-NEOs [Member] Member units acquired, units (in shares) Members Equity Units Acquired During Period Member units acquired during period shares. Calculation of Basic and Diluted Net Earnings (Loss) Per Share/Unit Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Tax credits Tax Credit Carryforward, Amount Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Hosting commitments Contractual Obligation, Hosting Commitments Contractual Obligation, Hosting Commitments Accrued Interest Forgiveness Accrued Interest Forgiveness [Member] Accrued interest forgiveness. Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Fixed coverage charge ratio Line Of Credit Facility, Fixed Coverage Charge Ratio Line Of Credit Facility, Fixed Coverage Charge Ratio Beginning balance Ending balance Accounts Receivable, Allowance for Credit Loss, Current Accrued compensation Increase Decrease In Accrued Compensation Increase decrease in Accrued compensation. Class A Common Stock Common Class A [Member] Common stock shares issued to continuing members (share) Exchange (cancellation) of shares Stock Issued During Period, Shares, Conversion of Convertible Securities Pay vs Performance Disclosure [Line Items] Line Of Credit Facility [Table] Line of Credit Facility [Table] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Accounts receivable Increase (Decrease) in Accounts Receivable Continuing Members Class B Units Continuing Members Class B Units [Member] Continuing members class B units. Earnings (Loss) Per Share Earnings Per Share, Policy [Policy Text Block] Operating lease liabilities Increase (Decrease) in Operating Lease Liability Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Deferred: Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Tax receivable agreement required to make payments to shareholders realized percentage of tax benefits in event that exchange of units to shares Tax Receivable Agreement Required To Make Payments To Shareholders Realized Percentage Of Tax Benefits In Event That Exchange Of Units To Shares Tax receivable agreement required to make payments to shareholders realized percentage of tax benefits in event that exchange of units to shares. Proceeds from the exercise of stock options Proceeds from Stock Options Exercised Award Timing Disclosures [Line Items] Other Performance Measure, Amount Other Performance Measure, Amount Research Tax Credit Carryforward Research Tax Credit Carryforward [Member] 2027 Finite-Lived Intangible Asset, Expected Amortization, Year Three Leases Lessee, Operating Leases [Text Block] Common stock, shares outstanding Common Stock, Shares, Outstanding Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Operating lease cost Operating Lease, Cost Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items] Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items] Basis of presentation and summary of significant accounting policies. Larry Madden [Member] Larry Madden Shares remained available for grant (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Long-term portion of operating lease liabilities Operating Lease, Liability, Noncurrent Segment Information Segment Reporting, Policy [Policy Text Block] Tax credits Deferred Tax Assets, Tax Credit Carryforwards Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Rent expense Operating Leases, Rent Expense Deferred revenue Contract with Customer, Liability, Current Plan Name Plan Name [Domain] Sale of stock, price per share (in dollars per share) Sale of Stock, Price Per Share Accrued member tax distributions Accrued Member Tax Distributions Accrued member tax distributions. Issuance of Class A common stock related to vesting of restricted stock units Stock Issued During Period, Value, Employee Benefit Plan Other assets Other Assets, Noncurrent Entity Tax Identification Number Entity Tax Identification Number Leases [Abstract] Gross Amount Finite-Lived Intangible Assets, Gross Schedule Of Finite Lived Intangible Assets [Table] Intangible Asset, Finite-Lived [Table] Gross increase based on tax positions related to prior years Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Repurchase of treasury shares in connection with the taxes paid related to net share settlement of equity awards (shares) Treasury Stock, Shares, Acquired Antidilutive Securities, Name Antidilutive Securities, Name [Domain] Foreign income tax Deferred Foreign Income Tax Expense (Benefit) Issuance of common stock in connection with equity-based compensation plans (shares) Stock Issued During Period, Shares, Employee Benefit Plan Contractual Obligation, to be Paid, Year Four Contractual Obligation, to be Paid, Year Four Supplier Supplier [Domain] Net cash provided by (used in) operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Treasury Stock Treasury Stock, Common [Member] Loan Agreement Loan Agreement [Member] Loan agreement. Plan Name Plan Name [Axis] Equity Components Equity Components [Axis] Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Award Timing Method Award Timing Method [Text Block] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Class A Units Members Equity Class A Units [Member] Members equity class A units. Accounts Receivable, Net of Allowances Accounts Receivable [Policy Text Block] Minority Interest [Line Items] Noncontrolling Interest [Line Items] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Insider Trading Policies and Procedures [Line Items] Beginning balance, convertible preferred units Ending balance, convertible preferred units Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests Use of Estimates Use of Estimates, Policy [Policy Text Block] Stock-based compensation included in capitalized software development costs Share-Based Payment Arrangement, Amount Capitalized Total operating expenses Costs and Expenses Business Acquisition, Acquiree Business Acquisition, Acquiree [Domain] Weighted-average shares of Class A common stock outstanding—diluted Undistributed Earnings Loss Attributable To All Unitholders Undistributed earnings (loss) attributable to all unitholders. Ownership Percentage Ownership Interest Percentage Ownership interest percentage. Adjustment to Compensation, Amount Adjustment to Compensation Amount Aggregate Intrinsic Value (in thousands)(1) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value Assets acquired Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Payables and Accruals [Abstract] Payables and Accruals [Abstract] Compensation Amount Outstanding Recovery Compensation Amount Earnings Per Share, Diluted [Abstract] Earnings Per Share, Diluted [Abstract] Supplemental disclosure of noncash investing and financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Entity Small Business Entity Small Business Developed technology Developed Technology Rights [Member] Accrued Liabilities Accounts Payable and Accrued Liabilities Disclosure [Text Block] Company Selected Measure Amount Company Selected Measure Amount Short-term lease commitment Short-Term Lease Commitment, Amount Payment of offering costs Payments of Debt Issuance Costs Tabular List, Table Tabular List [Table Text Block] Total deferred tax assets Deferred Tax Assets, Net 2028 Lessee, Operating Lease, Liability, to be Paid, Year Five Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Accounts Payable and Accrued Liabilities Accounts Payable And Accrued Liabilities Current [Member] Accounts payable and accrued liabilities current. Debt instrument forgiveness Debt Instrument, Decrease, Forgiveness Sales and marketing Selling and Marketing Expense [Member] Repurchase of stock related to the stock repurchase program Stock Repurchased During Period, Value Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Summary of Changes in Allowance for Doubtful Accounts Accounts Receivable, Allowance for Credit Loss [Table Text Block] Lessee Lease Description [Line Items] Lessee, Lease, Description [Line Items] Accrued liabilities Total accrued liabilities Accrued Liabilities, Current Total shares excluded from earnings (loss) per share of Class A common stock/unit—diluted (shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Impairment of other long lived assets Impairment of Long-Lived Assets to be Disposed of Summary of Effect of Changes in Ownership Interest in Viant Technology LLC on Equity Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Table Text Block] Credit Facility Credit Facility [Domain] Technology and development Technology And Development Expenses Technology and development expenses. Unrecognized stock-based compensation expected to be recognized Unrecognized stock-based compensation expected to be recognized Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Foreign income tax Current Foreign Tax Expense (Benefit) Current assets: Assets, Current [Abstract] Goodwill Goodwill Supplier One Supplier One [Member] Supplier one. Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Repurchase of stock related to tax withholdings on vested equity awards Payment, Tax Withholding, Share-Based Payment Arrangement Distributed earnings per unit—basic (dollars per share) Earnings Per Share, Basic, Distributed Treasury stock, shares Beginning balance, treasury stock (shares) Ending balance, treasury stock (shares) Treasury Stock, Common, Shares Summary Ownership of Viant Technology LLC Schedule Of Noncontrolling Ownership Interests Table [Table Text Block] Schedule of noncontrolling ownership interests. Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Temporary Equity Value Effect Of Reorganization Transactions Temporary Equity Value Effect Of Reorganization Transactions Temporary equity, value, effect of reorganization transactions. Employee Stock Option Share-Based Payment Arrangement, Option [Member] Short-term lease cost Short-Term Lease, Cost Issuance of Class A common stock in initial public offering, net of underwriting and offering costs (shares) Number Of Class A Common Shares Issued And Number Of Shares Converted From Class B Common Stock To Class A Common Stock During Period Including Those Related To Reorganization Transactions And Initial Public Offering Number of Class A common shares issued and number of shares converted from Class B common stock to Class A common stock during the period, including those related to reorganization transactions and an initial public offering. Vested (dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Depreciation Depreciation 2025 Lessee, Operating Lease, Liability, to be Paid, Year One Larry Madden Trading Arrangement, Class A Common Stock [Member] Larry Madden Trading Arrangement, Class A Common Stock Preferred stock, shares outstanding Preferred Stock, Shares Outstanding Repayment of revolving credit facility Repayments of Lines of Credit Other, net Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Security Exchange Name Security Exchange Name Debt instrument, basis spread on variable rate plus margin Debt Instrument, Basis Spread on Variable Rate Exchange basis for continuing members Continuing Members, Exchange Basis Continuing Members, Exchange Basis Award Type Award Type [Axis] Net deferred tax (liabilities) assets Deferred Tax Liabilities, Net Earnings Per Share, Basic [Abstract] Earnings Per Share, Basic [Abstract] Exercised Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Property, equipment, and software, net Total property, equipment, and software, net Property, Plant and Equipment, Net ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag State and local income tax Current State and Local Tax Expense (Benefit) Total liabilities Liabilities Noncontrolling interests Equity, Attributable to Noncontrolling Interest Undistributed earnings (loss) per unit—basic (dollars per share) Earnings Per Share, Basic, Undistributed Number of reporting units Number of Reporting Units Common stock, par value per share Common Stock, Par or Stated Value Per Share Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Remaining Weighted- Average Useful Life (years) Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life Revolving Credit Facility Revolving Credit Facility [Member] Expiration Date Trading Arrangement Expiration Date Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward] Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward] Provision for doubtful accounts Accounts Receivable, Credit Loss Expense (Reversal), Rounding Accounts Receivable, Credit Loss Expense (Reversal), Rounding Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Current portion of operating lease liabilities Less: Operating lease liabilities, current Operating Lease, Liability, Current Total Shareholder Return Amount Total Shareholder Return Amount Common stock, shares issued Common Stock, Shares, Issued Entity Entity [Domain] Undistributed Earnings (Loss) Allocated to Participating Securities, Basic Undistributed Earnings (Loss) Allocated to Participating Securities, Basic Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Senior secured revolving credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Concentration risk, percentage Concentration Risk, Percentage Income (loss) before income taxes Income (Loss), Including Portion Attributable to Noncontrolling Interest, before Tax Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards Computer equipment Computer Equipment [Member] Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Less: Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Cash and cash equivalents Cash Total property, equipment, and software Property, Plant and Equipment, Gross Exercise of stock options (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Common stock, shares authorized (shares) Common Stock, Shares Authorized Weighted average interest rate Long-Term Debt, Weighted Average Interest Rate, over Time Diluted (shares) Shares of Class B common stock Weighted Average Number of Shares Outstanding, Diluted MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Numerator Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Total stockholders' equity attributable to Viant Technology Inc. Equity, Attributable to Parent Subtotal Deferred Tax Assets, Gross Treasury stock, at cost; 1,565,373 and 153,875 shares held Treasury Stock, Value Entity Voluntary Filers Entity Voluntary Filers Operating Lease [Domain] Operating Lease [Domain] Operating Lease [Domain] Lessee operating lease renewal term Lessee, Operating Lease, Renewal Term Total deferred provision Deferred Income Tax Expense (Benefit) Property, Equipment and Software, Net Property, Plant and Equipment Disclosure [Text Block] Accrued compensation Accrued Salaries, Current Purchased software Software and Software Development Costs [Member] Concentration Risk Type Concentration Risk Type [Domain] Expenses incurred Selling, General and Administrative Expense Write-offs, net of recoveries Accounts Receivable, Allowance for Credit Loss, Writeoff Accounts receivable, net of allowances Accounts Receivable, after Allowance for Credit Loss, Current Granted (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Percentage of interest held Percentage of economic interest held Subsidiary, Ownership Percentage, Parent Equity incentive plan number of units, authorized (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Sale of Stock Sale of Stock [Domain] Other liabilities Increase (Decrease) in Other Operating Liabilities Carrying value of long-term debt Long-Term Debt Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Document Fiscal Period Focus Document Fiscal Period Focus All Executive Categories All Executive Categories [Member] 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Two Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Weighted-Average Remaining Contractual Term (years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Assets Assets [Abstract] Expected dividend yield Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Dividend Rate Document Type Document Type Customer Two Customer Two [Member] Customer two. Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Effect of Reorganization Transactions (shares) Stock Issued During Period Share Effect Of Reorganization Transactions Stock issued during period, share, effect of reorganization transactions. Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Viant Technology Inc Viant Technology Inc [Member] Viant Technology Inc. Document Annual Report Document Annual Report Phantom Unit Plan Phantom Unit Plan [Member] Phantom unit plan. Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Schedule of Interest Cost Schedule Of Interest Cost Table [Table Text Block] Schedule of interest cost. Members' Equity Members Equity [Member] Members Equity. Vested (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Effect of Reorganization Transactions (shares) Temporary Equity Share Effect Of Reorganization Transactions Temporary equity, share, effect of reorganization transactions. Summary of Changes in Deferred Revenue Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Summary of Estimated Future Amortization of Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Risk-free interest rate Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Members equity units received in exchange of units Members Equity Units Received During Period Conversion Of Units Members equity units received during period conversion of units. Maximum Maximum [Member] Amortization Amortization of Intangible Assets Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Intangible assets, net Net Carrying Amount Finite-Lived Intangible Assets, Net Antidilutive Securities Antidilutive Securities [Axis] Convertible Preferred Units Convertible Preferred Stock [Member] Accounts payable Accounts Payable, Current Liabilities Liabilities [Abstract] Less: Net income (loss) attributable to noncontrolling interests Preferred Stock Dividends, Income Statement Impact Leasehold improvements Leasehold Improvements [Member] Weighted average grant date fair value of units, expired (dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Summary of Assumptions used in Fair Value of Stock Options Granted Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Current Fiscal Year End Date Current Fiscal Year End Date Total lease cost Lease, Cost Advertising Agency B Advertising Agency Two [Member] Advertising agency two. Restricted stock units Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract] Statistical Measurement Statistical Measurement [Axis] PEO Name PEO Name Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Award Type Award Type [Domain] Loan Restructuring Modification Loan Restructuring Modification [Domain] Name Outstanding Recovery, Individual Name Disaggregation Of Revenue [Line Items] Disaggregation of Revenue [Line Items] Goodwill impairment Goodwill, Impairment Loss Variable lease cost Variable Lease, Cost Operating lease weighted average incremental borrowing rate Operating Lease Weighted Average Incremental Borrowing Rate Operating lease weighted average incremental borrowing rate. Exchange of Class B common stock for Class A common stock Stock Issued During Period, Value, Conversion of Units Larry Madden Trading Arrangement, Shares Issued Upon Vesting Of Restricted Stock Units [Member] Larry Madden Trading Arrangement, Shares Issued Upon Vesting Of Restricted Stock Units Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Over-time revenue Transferred over Time [Member] Money market funds Money Market Funds, at Carrying Value Supplier Concentration Risk Supplier Concentration Risk [Member] Non-PEO NEO Non-PEO NEO [Member] Number of supplier Number Of Supplier Number of supplier. Additional Paid-In Capital Additional Paid-in Capital [Member] Allocation of equity to noncontrolling interests Stock Issued During Period Value Allocation Of Equity To Non Controlling Interests Stock issued during period, value, allocation of equity to non-controlling interests. Award Timing Predetermined Award Timing Predetermined [Flag] Customer relationships Customer Relationships [Member] Recently Issued Accounting Pronouncements and Recently Adopted Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Treasury Stock Treasury Stock Policy [Policy Text Block] Treasury stock. Diluted (dollars per share) Total earnings (loss) per Class A common stock/unit—diluted (dollars per share) Earnings Per Share, Diluted Class of Stock Class of Stock [Axis] Finite-Lived Intangible Assets by Major Class Finite-Lived Intangible Assets by Major Class [Axis] Incentive Units Incentive Units [Member] Incentive unit. Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Summary of Amortization Recorded in Consolidated Statements of Operations Finite-Lived Intangible Assets Amortization Expense [Table Text Block] Noncash lease expense Operating Lease, Right-of-Use Asset, Periodic Reduction Name Measure Name State State and Local Jurisdiction [Member] Entity Interactive Data Current Entity Interactive Data Current Total current provision Current Income Tax Expense (Benefit) Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Common Units Member Units [Member] Ownership Ownership [Axis] Investment in Partnership Deferred Tax Assets, Investment in Subsidiaries Deferred tax liabilities: Deferred Tax Liabilities, Gross [Abstract] Preferred stock, shares issued Preferred Stock, Shares Issued Customer Customer [Axis] Disaggregation Of Revenue [Table] Disaggregation of Revenue [Table] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Transfers to noncontrolling interests: Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Net [Abstract] Distribution threshold amount Share Based Compensation Arrangement By Share Based Payment Award Distribution Threshold Amount Share-based compensation arrangement by share-based payment award, distribution threshold amount. Other, net Deferred Tax Liabilities, Other Sales and marketing Selling and Marketing Expense Total fair value of RSUs, as of their respective vesting dates Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Income (loss) before income taxes Net income (loss) Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Stock Issued During Period Value Effect Of Reorganization Transactions Stock Issued During Period Value Effect Of Reorganization Transactions Stock issued during period, value, effect of reorganization transactions. Technology and development Technology And Development [Member] Technology and development. Provision for (benefit from) income taxes Income tax (benefit) provision Income Tax Expense (Benefit) Bears interest at an annual rate Debt Instrument, Interest Rate, Stated Percentage Accounts Receivable, Allowance for Credit Loss [Roll Forward] Accounts Receivable, Allowance for Credit Loss [Roll Forward] Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Unrecognized stock-based compensation expected to be recognized over a weighted-average period Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Revenue Revenue from Contract with Customer, Excluding Assessed Tax Net Income Loss Prior To Reorganization Transactions Net Income Loss Prior To Reorganization Transactions Net income (loss) prior to reorganization transactions. Total other expense (income), net Nonoperating Income (Expense) Concentration Risk Benchmark Concentration Risk Benchmark [Domain] Invoice payment terms Invoice Payment Terms, Term Invoice Payment Terms, Term Auditor Firm ID Auditor Firm ID Effective tax rate Total effective rate Effective Income Tax Rate Reconciliation, Percent Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Income (loss) from operations Operating Income (Loss) Income Tax Jurisdiction Income Tax Jurisdiction [Axis] Variable Rate Variable Rate [Domain] Stock-based compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-Based Payment Arrangement, Percent Total liabilities and stockholders’ equity Liabilities and Equity Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] All Adjustments to Compensation All Adjustments to Compensation [Member] Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Additional paid-in capital Additional Paid in Capital Capitalized software development costs Capitalized Software Development Costs [Member] Capitalized software development costs. Minority Interest [Table] Noncontrolling Interest [Table] Tax Credit Carryforward [Axis] Tax Credit Carryforward [Axis] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Legal Entity Legal Entity [Axis] Interest expense (income), net Interest Income (Expense), Nonoperating Finite-Lived Intangible Assets, Major Class Name Finite-Lived Intangible Assets, Major Class Name [Domain] Noncurrent portion of deferred rent Deferred Rent Credit, Noncurrent Tax Receivable Agreement Tax Receivable Agreement Policy [Policy Text Block] Tax receivable agreement. Customer One Customer One [Member] Customer One. Payments to acquire units Payments To Acquire Member Units Payments to acquire member units. Operating lease assets obtained in exchange for operating lease liabilities 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. Weighted average grant date fair value of units, canceled (dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Expected term (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term Entity Address, State or Province Entity Address, State or Province Property Plant And Equipment [Line Items] Property, Plant and Equipment [Line Items] Viant Technology LLC Viant Technology L L C [Member] Viant Technology LLC. Statement [Line Items] Statement [Line Items] 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] IPO IPO [Member] Deferred Offering Costs Deferred Charges, Policy [Policy Text Block] 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. 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 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) 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. U.S. statutory federal income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Cash settlement Decrease In Revenue Recognition Due To Cash Settlement For Termination Of Deferred Revenue Liabilities Decrease in revenue recognition due to cash settlement for termination of deferred revenue liabilities. Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Abstract] Exercise Price Award Exercise Price Significant Portion of Deferred Tax Assets and Deferred Tax Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Loss Per Share Earnings Per Share [Text Block] Arrangement Duration Trading Arrangement Duration Operating loss carryforwards Operating Loss Carryforwards Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Operating expenses: Costs and Expenses [Abstract] Less: Imputed interest Lessee Operating Lease Liability Imputed Interest Lessee operating lease liability imputed interest. Goodwill and Intangible Assets, Net Goodwill and Intangible Assets Disclosure [Text Block] Stockholders’ equity Equity, Attributable to Parent [Abstract] Granted (dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Deferred rent reclassified to operating leases Reclassification Of Deferred Rent To Operating Lease Liability Reclassification of deferred rent to operating lease liability. Weighted average remaining contractual term, vested and exercisable Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Exercisable Weighted Average Remaining Contractual Term Share based compensation arrangement by share based payment award options vested and exercisable weighted average remaining contractual term. Federal Domestic Tax Jurisdiction [Member] Units owned (shares) Number Of Units Owned Number of units owned. Income Taxes Income Tax, Policy [Policy Text Block] Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Expected Duration of Greater Than One Year Long-Term Contract with Customer [Member] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Unrecognized Tax Benefits [Roll Forward] Unrecognized Tax Benefits [Roll Forward] 2028 Finite-Lived Intangible Asset, Expected Amortization, Year Four All Individuals All Individuals [Member] Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Trademarks/tradenames Trademarks and Trade Names [Member] Vested and exercisable (shares) Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Exercisable Number Of Shares Share based compensation arrangement by share based payment award options vested and exercisable number of shares. PEO PEO [Member] Contract with Customer, Duration Contract with Customer, Duration [Domain] Variable Rate Variable Rate [Axis] Credit Concentration Risk Credit Concentration Risk [Member] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Name Trading Arrangement, Individual Name Other expense Other Nonoperating Income (Expense) Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Income Tax Disclosure [Line Items] Income Tax Disclosure [Line Items] Income tax disclosure line items. Change from net income (loss) attributable to Viant Technology Inc. and transfers to noncontrolling interests Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Change Due to Net Income Attributable to Parent and Effects of Changes, Net Long-Lived Tangible Asset Long-Lived Tangible Asset [Axis] Entity Public Float Entity Public Float Operating leases for office space remaining lease terms Lessee, Operating Lease, Remaining Lease Term Exchange of noncontrolling interests, shares Noncontrolling Interests Number Of Shares Exchanged Noncontrolling interests, number of shares exchanged. Schedule of Depreciation Schedule Of Depreciation Expense Table [Table Text Block] Schedule of depreciation expense. Beginning balance, treasury stock Ending balance, treasury stock Treasury Stock, Common, Value Capitalized software development costs Payments to Develop Software Facility fee for undrawn amounts Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Schedules of Concentrations of Credit Risk Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Lender Name Lender Name [Axis] Shares reserved for issuance (shares) Common Stock, Capital Shares Reserved for Future Issuance Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Related and Nonrelated Parties Related and Nonrelated Parties [Domain] Beginning balance (shares) Ending balance (shares) Shares, Outstanding Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Class B Units Members Equity Class B Units [Member] Members equity class B units. 2021 LTIP Two Thousand And Twenty One Long Term Incentive Plan [Member] Two thousand and twenty one long term incentive plan. Local Phone Number Local Phone Number Supplier Supplier [Axis] Nature Of Operations [Line Items] Nature Of Operations [Line Items] Nature of Operations. Deferred tax assets, valuation allowance Valuation allowance Deferred Tax Assets, Valuation Allowance Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Risk free interest rate, maximum Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum Expected volatility Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate Summary of RSU Activity Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Repurchase of stock related to the stock repurchase program (shares) Stock Repurchased During Period, Shares Exchange of Class B common stock for Class A common stock (shares) Stock Issued During Period, Shares, Conversion of Units Related Party Relationships Related Party Relationships Policy [Policy Text Block] Related party relationships. Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] SOFR Secured Overnight Financing Rate (SOFR) [Member] PEO Total Compensation Amount PEO Total Compensation Amount U.S. federal income tax Deferred Federal Income Tax Expense (Benefit) Long-Lived Tangible Asset Long-Lived Tangible Asset [Domain] Summary of Accrued Liabilities Schedule of Accrued Liabilities [Table Text Block] Statement of Income Location, Balance Statement of Income Location, Balance [Axis] Entity Ex Transition Period Entity Ex Transition Period Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Payments of stock issuance costs Payments of Stock Issuance Costs Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Five Debt Disclosure [Abstract] Debt Disclosure [Abstract] Reissuance of treasury stock in connection with equity-based compensation plans Stock Issued During Period, Value, Treasury Stock Reissued Common Stock Common Stock [Member] Measure: Measure [Axis] Basis of Presentation and Principles of Consolidation Basis Of Presentation And Principles Of Consolidation Policy [Policy Text Block] Basis of presentation and principles of consolidation. Impairment of Long-Lived Assets Impairment or Disposal of Long-Lived Assets, Including Intangible Assets, Policy [Policy Text Block] Gross increase based on tax positions related to current year Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Contractual Obligation, to be Paid, Year Three Contractual Obligation, to be Paid, Year Three Carrying value Line of Credit Facility, Maximum Amount Outstanding During Period Preferred stock, shares authorized (shares) Preferred Stock, Shares Authorized Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Common stock shares issued and sold (shares) Stock Issued During Period, Shares, New Issues Number of customer Number Of Customer Number of customer. Entity Emerging Growth Company Entity Emerging Growth Company Entity Central Index Key Entity Central Index Key General and administrative General and Administrative Expense [Member] Lessee Lease Description [Table] Lessee, Lease, Description [Table] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Expected volatility, minimum Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Equity Component Equity Component [Domain] Preferred stock, par value per share Preferred Stock, Par or Stated Value Per Share Beginning balance, convertible preferred units (shares) Ending balance, convertible preferred units (shares) Temporary Equity, Shares Outstanding Percentage of exclusive of non-controlling interest due to income tax expense/(benefit) not recognize on share of pre-tax book income (loss) Percentage Of Exclusive Of Non Controlling Interest Due To Income Tax Expense Benefit Not Recognize On Share Of Pre Tax Book Income Loss Percentage of exclusive of non-controlling interest due to income tax expense/(benefit) not recognize on share of pre-tax book income (loss). Nonqualified stock options Incremental Common Shares Attributable to Dilutive Effect of Conversion of Preferred Stock Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Accrued member tax distributions Adjustments To Additional Paid In Capital Accrued Member Tax Distributions Adjustments to additional paid in capital, accrued member tax distributions. Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Audit Information [Abstract] Audit Information Entity Shell Company Entity Shell Company Advertising Agency A Advertising Agency One [Member] Advertising agency one. Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Comprehensive Income (Loss) Comprehensive Income, Policy [Policy Text Block] Class B Common Stock Common Class B [Member] Title Trading Arrangement, Individual Title Standby Letters of Credit Standby Letters of Credit [Member] Statement [Table] Statement [Table] Beginning balance of unrecognized tax benefits Ending balance of unrecognized tax benefits Unrecognized Tax Benefits City Area Code City Area Code Current liabilities: Liabilities, Current [Abstract] Auditor Location Auditor Location Tax receivable agreement expected remaining tax benefit percentage Tax Receivable Agreement Expected Remaining Tax Benefit Percentage Tax receivable agreement expected remaining tax benefit percentage. Common units, units outstanding (shares) Common Unit, Outstanding Share-based compensation arrangement by share-based payment award, initial public offering lock-up period Share Based Compensation Arrangement By Share Based Payment Award Initial Public Offering Lock Up Period Share-based compensation arrangement by share-based payment award, initial public offering lock-up period. Reissuance of treasury stock in connection with equity-based compensation plans (shares) Stock Issued During Period, Shares, Treasury Stock Reissued Cash paid for interest Interest Paid, Excluding Capitalized Interest, Operating Activities Michigan Office Space Michigan Office Space [Member] Michigan Office Space IRIS.TV IRIS.TV [Member] IRIS.TV Revenue Recognition Revenue [Policy Text Block] Net income (loss) attributable to Viant Technology Inc.—basic Adjusted Net Income Loss Attributable To Common Unitholders Adjusted net income (loss) attributable to common unitholders. Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Concentration Risk Benchmark Concentration Risk Benchmark [Axis] Loss on disposal of assets Gain (Loss) on Disposition of Assets Total current assets Assets, Current Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Accrued liabilities Increase (Decrease) in Accrued Liabilities Document Information [Line Items] Document Information [Line Items] Ad impressions Cost Per Mile Pricing Option, Number of Ad Impressions Cost Per Mile Pricing Option, Number of Ad Impressions Tax receivable agreement interest payments accrued basis spread rate Tax Receivable Agreement Interest Payments Accrued Basis Spread Rate Tax receivable agreement interest payments accrued basis spread rate. Long-term debt Long-Term Debt, Excluding Current Maturities Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted-average grant-date fair value of stock options granted (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Income Taxes and Tax Receivable Agreement Income Tax Disclosure [Text Block] 2027 Lessee, Operating Lease, Liability, to be Paid, Year Four Earnings (loss) per Class A common stock: Earnings Per Share [Abstract] Accumulated deficit Retained Earnings (Accumulated Deficit) Class of Stock Class of Stock [Domain] Security deposit Security Deposit Consolidated Revenue Revenue from Contract with Customer Benchmark [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Schedule of Debt and Revolving Credit Facilities Schedule of Debt [Table Text Block] General and administrative General and Administrative Expense Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Equity Awards Adjustments Equity Awards Adjustments [Member] Operating lease liabilities Operating Lease, Liability Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Earnings (Loss) Per Unit Earnings Loss Per Unit Policy [Policy Text Block] Earnings loss per unit. Underlying Securities Award Underlying Securities Amount London Interbank Offered Rate (LIBOR) 1 London Interbank Offered Rate (LIBOR) 1 [Member] London Interbank Offered Rate (LIBOR) 1 Credit Facility Credit Facility [Axis] Amendment Flag Amendment Flag Cumulative impact of accounting adoption Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease) JOBS Act Election as an Emerging Growth Company JOBS Act Election, Policy [Policy Text Block] JOBS Act Election, Policy Entity Registrant Name Entity Registrant Name Cash paid for acquisitions Payments to Acquire Businesses, Gross Point-in-time revenue Transferred at Point in Time [Member] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Depreciation and amortization Depreciation, Depletion and Amortization Timing of Transfer of Good or Service Timing of Transfer of Good or Service [Axis] State and local income tax Deferred State and Local Income Tax Expense (Benefit) Fair Value as of Grant Date Award Grant Date Fair Value Antidilutive Securities Excluded From Earnings Loss Per Share [Abstract] Antidilutive Securities Excluded From Earnings Loss Per Share [Abstract] Antidilutive securities excluded from earnings (loss) per share. Permanent items Effective Income Tax Rate Reconciliation Permanent Items Effective Income Tax Rate Reconciliation Permanent Items Customer Concentration Risk Customer Concentration Risk [Member] Basis Of Presentation And Summary Of Significant Accounting Policies [Table] Basis Of Presentation And Summary Of Significant Accounting Policies [Table] Basis of presentation and summary of significant accounting policies. Affiliated Entity Affiliated Entity [Member] Operating Expenses Selling, General and Administrative Expenses, Policy [Policy Text Block] Revolving Credit Facility and PPP Loan Debt Disclosure [Text Block] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Summary of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Less: Commitments for leases not yet commenced Lessee Operating Lease Liability Commitment For Leases Not Yet Commenced Lessee Operating Lease Liability Commitment For Leases Not Yet Commenced Issuance of Class A common stock related to vesting of restricted stock units Stock Issued During Period, Value, New Issues Entity Address, Postal Zip Code Entity Address, Postal Zip Code Collaborative Arrangement and Arrangement Other than Collaborative Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Advertising costs Advertising Expense Summary of Stock-based Compensation Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Paycheck Protection Program Loan Paycheck Protection Program Loan Policy [Policy Text Block] Paycheck protection program loan. Restatement Determination Date: Restatement Determination Date [Axis] Collaborative Arrangement and Arrangement Other than Collaborative Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Title of 12(b) Security Title of 12(b) Security Concentration Risk Type Concentration Risk Type [Axis] Common stock, $0.001 par value Common Stock, Value, Issued Document Financial Statement Error Correction [Flag] Document Financial Statement Error Correction [Flag] Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Schedule of Estimated Useful Lives of Property, Equipment and Software Schedule Of Property Plant And Equipment Estimated Useful Life Table [Table Text Block] Schedule of property plant And equipment estimated useful life. State and local taxes, net of federal benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value Auditor Name Auditor Name Other, net Deferred Tax Assets, Other Finite Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Customer Three Customer Three [Member] Customer Three Canceled/forfeited (dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Gain on extinguishment of debt Gain (Loss) on Extinguishment of Debt Impairment of intangible assets Impairment of Intangible Assets (Excluding Goodwill) Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Net loss Net Income Loss Subsequent To Reorganization Transactions Net income (loss) subsequent to reorganization transactions. Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Preferred stock, $0.001 par value Preferred Stock, Value, Issued Property, equipment and software, estimated useful lives Property, Plant and Equipment, Useful Life Accrued liabilities Accrued Liabilities Total deferred tax liabilities Deferred Tax Liabilities, Gross Common stock shares issued for each membership unit (share) Common Stock Shares Issued For Each Membership Unit Common stock shares issued for each membership unit. Noncontrolling Interests Noncontrolling Interest Disclosure [Text Block] Basic (dollars per share) Total earnings (loss) per Class A common stock/unit—basic (dollars per share) Earnings Per Share, Basic Nonqualified Stock Options Nonqualified Stock Options [Member] Nonqualified stock options. Accounts payable Increase (Decrease) in Accounts Payable Cash paid for amounts included in operating lease liabilities Operating Lease, Payments Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Contractual obligation amount Contractual Obligation Furniture, fixtures and office equipment Furniture Fixtures And Office Equipment [Member] Furniture, fixtures and office equipment. Nonqualified stock options, contractual terms Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period Ownership Ownership [Domain] Contractual Obligation, to be Paid, Year One Contractual Obligation, to be Paid, Year One Capitalized assets financed by accounts payable and accrued liabilities Capital Expenditures Incurred but Not yet Paid Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Earnings (loss) per share of Class A common stock—diluted Net Income (Loss) Available to Common Stockholders, Basic Property, Equipment and Software, Net Property, Plant and Equipment, Policy [Policy Text Block] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Income tax expense Income Tax Expense (Benefit), Rounding Income Tax Expense (Benefit), Rounding Basis Of Presentation And Summary Of Significant Accounting Policies [Abstract] Basis Of Presentation And Summary Of Significant Accounting Policies [Abstract] Basis of Presentation and Summary of Significant Accounting Policies. Total current liabilities Liabilities, Current Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Weighted average shares of Class A common stock outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Total assets Assets Concentration of Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] 2025 Finite-Lived Intangible Asset, Expected Amortization, Year One Platform operations Cost of Goods and Services Sold Share based payment award equity instruments other than options grants in period (shares) Granted (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Underwriters Over-Allotment Option [Member] Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Paycheck Protection Program Loan Paycheck Protection Program Loan [Member] Paycheck Protection Program Loan. Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Commitments and contingencies (Note 13) Commitments and Contingencies Underwrites options exercised shares issued (shares) Stock Issued During Period Shares Underwrites Options Exercised Stock issued during period shares underwrites options exercised. Stock-Based Compensation Share-Based Payment Arrangement [Policy Text Block] Risk free interest rate, minimum Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum Schedule of Effective Income Tax Rate Reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Termination Date Trading Arrangement Termination Date Expected volatility, maximum Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum Nature of Operations Nature of Operations [Text Block] Schedule Of Related Party Transactions By Related Party [Table] Related Party Transaction [Table] Revenues Revenues 2026 Lessee, Operating Lease, Liability, to be Paid, Year Two Income Tax Disclosure [Table] Income Tax Disclosure [Table] Income tax disclosure. Stock-based Compensation Share-Based Payment Arrangement [Text Block] Undrawn availability Line Of Credit Facility, Undrawn Availability Percentage Line Of Credit Facility, Undrawn Availability Percentage Uncertain tax position Effective Income Tax Rate Reconciliation, Tax Contingency, Percent Entity Address, City or Town Entity Address, City or Town Proceeds from issuance of debt Proceeds from Issuance of Long-Term Debt Deferred tax assets: Deferred Tax Assets, Gross [Abstract] Leases Lessee, Leases [Policy Text Block] Debt Instrument Debt Instrument [Axis] Summary of Stock Option/Incentive Activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Intrinsic value Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value Noncontrolling Interest [Abstract] Noncontrolling Interest [Abstract] Ownership percentage by non-controlling interests Economic Interests Ownership Percentage Economic interests ownership percentage. Stock/Unit-Based Compensation expense Compensation cost Share-Based Payment Arrangement, Expense Net income (loss) attributable to Viant Technology Inc. Net income (loss) attributable to Viant Technology Inc. Net Income (Loss) Attributable to Parent Trading Arrangement: Trading Arrangement [Axis] Platform operations Platform Operations [Member] Platform operations. Accounting Standards Update 2016-13 Accounting Standards Update 2016-13 [Member] Weighted average grant date fair value of units, granted (dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Canceled/forfeited (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Business Acquisition Business Acquisition [Axis] Summary of Balances of Intangibles Assets and Accumulated Amortization Schedule of Finite-Lived Intangible Assets [Table Text Block] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] PNC Bank P N C Bank [Member] PNC Bank. 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] Common stock voting rights percentage Common Stock Voting Rights Percentage Common stock voting rights percentage. Denominator Dividends, Common Stock Other accrued liabilities Other Accrued Liabilities, Current Name Forgone Recovery, Individual Name Current portion of deferred rent Deferred Rent Credit, Current Operating lease weighted average remaining lease term Operating Lease, Weighted Average Remaining Lease Term 2029 Finite-Lived Intangible Asset, Expected Amortization, Year Five Document Period End Date Document Period End Date Sale of Stock Sale of Stock [Axis] Operating Lease [Axis] Operating Lease [Axis] Operating Lease Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Accrued traffic acquisition costs Accrued Traffic Acquisition Costs Accrued traffic acquisition costs. 2029 Total undiscounted future lease payments Lessee, Operating Lease, Liability, to be Paid RSUs outstanding, beginning balance (shares) RSUs outstanding, ending balance (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Deferred revenue Increase (Decrease) in Deferred Revenue Expired (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Expirations in Period Line of Credit Facility, Lender Line of Credit Facility, Lender [Domain] Insider Trading Arrangements [Line Items] Income passed through to noncontrolling interests Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent Line Of Credit Facility [Line Items] Line of Credit Facility [Line Items] Payment of member tax distributions Payment Of Member Tax Distributions Payment of member tax distributions. 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 2026 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 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 Executive compensation 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] 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. Subsidiary, Ownership Percentage, Noncontrolling Owner Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Meredith Corporation Meredith Corporation [Member] Meredith Corporation. Related and Nonrelated Parties Related and Nonrelated Parties [Axis] Basic (shares) Anti-dilutive shares excluded from earnings (loss) per share of Class A common stock—diluted: Weighted Average Number of Shares Outstanding, Basic Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Document Information [Table] Document Information [Table] Total equity Beginning balance Ending balance Equity, Including Portion Attributable to Noncontrolling Interest Restricted Stock Units Restricted Stock Units (RSUs) [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Executive Category: Executive Category [Axis] Name Awards Close in Time to MNPI Disclosures, Individual Name Contract with Customer, Duration Contract with Customer, Duration [Axis] Canceled (shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period Schedule of Provision for Income Taxes Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Repurchase of stock related to the stock repurchase program Payments for Repurchase of Preferred Stock and Preference Stock Entity Filer Category Entity Filer Category Revenue, remaining performance obligation amount Revenue, Remaining Performance Obligation, Amount Statement of Income Location, Balance Statement of Income Location, Balance [Domain] Company Selected Measure Name Company Selected Measure Name