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  <xs:element id="mgni_DavidDayMember" abstract="true" name="DavidDayMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_ConversionTermIMember" abstract="true" name="ConversionTermIMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_SpotXIncAndServeMotionIncMember" abstract="true" name="SpotXIncAndServeMotionIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_OfficeLeaseMember" abstract="true" name="OfficeLeaseMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_LeasesLiabilitiesNoncurrent" abstract="false" name="LeasesLiabilitiesNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_ScheduleOfInternalUseSoftwareCostsTableTextBlock" abstract="false" name="ScheduleOfInternalUseSoftwareCostsTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedAndVestedButDeferredWeightedAverageGrantDateFairValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedAndVestedButDeferredWeightedAverageGrantDateFairValue" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:perShareItemType"/>
  <xs:element id="mgni_NonCancelableInventoryAndOtherServicesPurchaseCommitmentsMemberMember" abstract="true" name="NonCancelableInventoryAndOtherServicesPurchaseCommitmentsMemberMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_ConversionTermVMember" abstract="true" name="ConversionTermVMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_AlternateBaseRateMember" abstract="true" name="AlternateBaseRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_ConversionTermIiMember" abstract="true" name="ConversionTermIiMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_DebtInstrumentCappedCallConversionPrice" abstract="false" name="DebtInstrumentCappedCallConversionPrice" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:perShareItemType"/>
  <xs:element id="mgni_LineOfCreditFacilityCovenantComplianceLeverageRatioMaximum" abstract="false" name="LineOfCreditFacilityCovenantComplianceLeverageRatioMaximum" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="mgni_A2014EmployeeStockPurchasePlanMember" abstract="true" name="A2014EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_NumberOfTranches" abstract="false" name="NumberOfTranches" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="mgni_BasisOfRevenueRecognitionAxis" abstract="true" name="BasisOfRevenueRecognitionAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="mgni_InternalUseSoftwareDevelopmentCostsNet" abstract="false" name="InternalUseSoftwareDevelopmentCostsNet" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_EmployeeSeveranceAndOneTimeTerminationBenefitsMember" abstract="true" name="EmployeeSeveranceAndOneTimeTerminationBenefitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_ServeMotionIncMember" abstract="true" name="ServeMotionIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_August2023RepurchasePlanMember" abstract="true" name="August2023RepurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_IncreaseDecreaseInAccountsPayableSeller" abstract="false" name="IncreaseDecreaseInAccountsPayableSeller" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_February2023RepurchasePlanMember" abstract="true" name="February2023RepurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_AmortizationOfDebtDiscountPremiumYearThree" abstract="false" name="AmortizationOfDebtDiscountPremiumYearThree" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_SeniorSecuredTermLoanFacilityMember" abstract="true" name="SeniorSecuredTermLoanFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_DebtInstrumentPeriodicPaymentPercentageOfPrincipal" abstract="false" name="DebtInstrumentPeriodicPaymentPercentageOfPrincipal" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="mgni_NumberOfProjects" abstract="false" name="NumberOfProjects" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="mgni_DebtIssuanceCostsAxis" abstract="true" name="DebtIssuanceCostsAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="mgni_DebtDiscountMember" abstract="true" name="DebtDiscountMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCash" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestrictedCash" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsCorrelationCoefficients" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsCorrelationCoefficients" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="mgni_AmortizationOfDebtIssuanceCostsAbstract" abstract="true" name="AmortizationOfDebtIssuanceCostsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="mgni_RestructuringChargesMergerAndAcquisitionAssumedLossContracts" abstract="false" name="RestructuringChargesMergerAndAcquisitionAssumedLossContracts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_BusinessAcquisitionEquityInterestIssuedOrIssuableElectedDecreaseValue" abstract="false" name="BusinessAcquisitionEquityInterestIssuedOrIssuableElectedDecreaseValue" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsSelectedPeerCompaniesWeightedAverageVolatilityRate" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsSelectedPeerCompaniesWeightedAverageVolatilityRate" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="mgni_DebtInstrumentConversionTermDomain" abstract="true" name="DebtInstrumentConversionTermDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_RestructuringReserveAndBusinessCombinationAcquisitionRelatedCosts" abstract="false" name="RestructuringReserveAndBusinessCombinationAcquisitionRelatedCosts" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_CustomerTwoMember" abstract="true" name="CustomerTwoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_AmortizationOfDebtIssuanceCostsYearFour" abstract="false" name="AmortizationOfDebtIssuanceCostsYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsExercisesinPeriodGross" abstract="false" name="SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsExercisesinPeriodGross" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="mgni_DataCentersForCloudBasedServicesMember" abstract="true" name="DataCentersForCloudBasedServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_RestructuringImpairmentsSettledWithoutCash" abstract="false" name="RestructuringImpairmentsSettledWithoutCash" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_CarbonAILimitedAndModeTechnologiesIncMember" abstract="true" name="CarbonAILimitedAndModeTechnologiesIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_DebtInstrumentsCappedCallsTransactionCosts" abstract="false" name="DebtInstrumentsCappedCallsTransactionCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_LeaseArrangementsDomain" abstract="true" name="LeaseArrangementsDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_BasisOfRevenueRecognitionDomain" abstract="true" name="BasisOfRevenueRecognitionDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_RestructuringChargesAndMergerRelatedCostsSettledWithoutCash" abstract="false" name="RestructuringChargesAndMergerRelatedCostsSettledWithoutCash" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_DebtInstrumentMaturityTriggerOutstandingPeriodPriorToMaturityDate" abstract="false" name="DebtInstrumentMaturityTriggerOutstandingPeriodPriorToMaturityDate" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="mgni_DebtDiscountReceivedDuringNoncashOrPartialNoncashTransaction" abstract="false" name="DebtDiscountReceivedDuringNoncashOrPartialNoncashTransaction" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" abstract="true" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="mgni_BusinessCombinationConsiderationTransferredWorkingCapitalAdjustments" abstract="false" name="BusinessCombinationConsiderationTransferredWorkingCapitalAdjustments" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_BusinessCombinationConsiderationTransferredIndemnificationClaimsHoldback" abstract="false" name="BusinessCombinationConsiderationTransferredIndemnificationClaimsHoldback" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_PercentageOfOutstandingBalanceHoldersAbleToCallDebtInTheEventOfDefault" abstract="false" name="PercentageOfOutstandingBalanceHoldersAbleToCallDebtInTheEventOfDefault" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="mgni_AmortizationOfDebtDiscountPremiumYearFour" abstract="false" name="AmortizationOfDebtDiscountPremiumYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_ExitCostsMember" abstract="true" name="ExitCostsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_InternalUseSoftwareDevelopmentCostsWriteoffs" abstract="false" name="InternalUseSoftwareDevelopmentCostsWriteoffs" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_PaymentsForCappedCallOptions" abstract="false" name="PaymentsForCappedCallOptions" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_DeferredTaxAssetLeaseLiability" abstract="false" name="DeferredTaxAssetLeaseLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_PerformanceSharesGrantedFebruary2022Member" abstract="true" name="PerformanceSharesGrantedFebruary2022Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceMeasurementPercentage" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceMeasurementPercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="mgni_GrossRevenueMember" abstract="true" name="GrossRevenueMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_SpotXIncMember" abstract="true" name="SpotXIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingThresholdConsecutiveTradingDays" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingThresholdConsecutiveTradingDays" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="mgni_DebtInstrumentOverAllotmentOptions" abstract="false" name="DebtInstrumentOverAllotmentOptions" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_DebtInstrumentOriginalIssueDiscountPercent" abstract="false" name="DebtInstrumentOriginalIssueDiscountPercent" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mgni_DebtInstrumentRedemptionMakeWholeFundamentalChangePeriod" abstract="false" name="DebtInstrumentRedemptionMakeWholeFundamentalChangePeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="mgni_AmortizationOfDebtIssuanceCostAndDiscount" abstract="false" name="AmortizationOfDebtIssuanceCostAndDiscount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_DeferredIncomeTaxLiabilitiesNetMember" abstract="true" name="DeferredIncomeTaxLiabilitiesNetMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_PerformanceSharesGrantedIn2022Member" abstract="true" name="PerformanceSharesGrantedIn2022Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_StockIssuedDuringPeriodSharesMerger" abstract="false" name="StockIssuedDuringPeriodSharesMerger" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="mgni_RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts" abstract="false" name="RestructuringChargesAndBusinessCombinationAcquisitionRelatedCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_ConvertibleSeniorNoteMember" abstract="true" name="ConvertibleSeniorNoteMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_PerformanceSharesGrantedApril2020Member" abstract="true" name="PerformanceSharesGrantedApril2020Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgni_EffectiveIncomeTaxRateReconciliationOfficersCompensationPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationOfficersCompensationPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
</xs:schema>
