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  <xs:element id="mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsAccountsReceivables" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsAccountsReceivables" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseLeaseAsset" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseLeaseAsset" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_DebtDiscountMember" abstract="true" name="DebtDiscountMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_PerformanceSharesGrantedApril2020Member" abstract="true" name="PerformanceSharesGrantedApril2020Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_SpotXIncAndServeMotionIncMember" abstract="true" name="SpotXIncAndServeMotionIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_AmortizationOfDebtDiscountPremiumYearFive" abstract="false" name="AmortizationOfDebtDiscountPremiumYearFive" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_AmortizationOfDebtIssuanceCostsYearOne" abstract="false" name="AmortizationOfDebtIssuanceCostsYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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_DebtInstrumentPeriodicPaymentPercentageOfPrincipal" abstract="false" name="DebtInstrumentPeriodicPaymentPercentageOfPrincipal" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mgni_AmortizationOfDebtDiscountPremiumRemainderOfFiscalYear" abstract="false" name="AmortizationOfDebtDiscountPremiumRemainderOfFiscalYear" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_SeniorSecuredRevolvingCreditFacilityMember" abstract="true" name="SeniorSecuredRevolvingCreditFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_DebtInstrumentConversionTermDomain" abstract="true" name="DebtInstrumentConversionTermDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_SharebasedPaymentArrangementTrancheFourMember" abstract="true" name="SharebasedPaymentArrangementTrancheFourMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_RestructuringImpairmentCosts" abstract="false" name="RestructuringImpairmentCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_AmortizationOfDebtDiscountPremiumYearTwo" abstract="false" name="AmortizationOfDebtDiscountPremiumYearTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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_DeferredFinancingCostsMember" abstract="true" name="DeferredFinancingCostsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <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_ServeMotionIncMember" abstract="true" name="ServeMotionIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_ConvertibleSeniorNoteMember" abstract="true" name="ConvertibleSeniorNoteMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <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_EvergreenAnnualIncrease" abstract="false" name="EvergreenAnnualIncrease" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingThresholdConsecutiveTradingDays" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingThresholdConsecutiveTradingDays" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="mgni_DebtInstrumentConversionTermAxis" abstract="true" name="DebtInstrumentConversionTermAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="mgni_AccountsReceivableCreditLossExpenseReversalGross" abstract="false" name="AccountsReceivableCreditLossExpenseReversalGross" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_AmortizationOfDebtDiscountPremiumYearOne" abstract="false" name="AmortizationOfDebtDiscountPremiumYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_RestrictedStockUnitsAndRestrictedStockAwardsMember" abstract="true" name="RestrictedStockUnitsAndRestrictedStockAwardsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <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_RestructuringReserveAndBusinessCombinationAcquisitionRelatedCosts" abstract="false" name="RestructuringReserveAndBusinessCombinationAcquisitionRelatedCosts" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_AccountsPayableSeller" abstract="false" name="AccountsPayableSeller" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_AmortizationOfDebtIssuanceCostsYearThree" abstract="false" name="AmortizationOfDebtIssuanceCostsYearThree" 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-types:domainItemType"/>
  <xs:element id="mgni_ConnectedTelevisionMember" abstract="true" name="ConnectedTelevisionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_DebtInstrumentRedemptionMakeWholeFundamentalChangePeriod" abstract="false" name="DebtInstrumentRedemptionMakeWholeFundamentalChangePeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <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_DataCentersForCloudBasedServicesMember" abstract="true" name="DataCentersForCloudBasedServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_MobileMember" abstract="true" name="MobileMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_LineOfCreditFacilityCovenantComplianceDebtUtilizationTriggeringLeverageRatioCompliancePercentage" abstract="false" name="LineOfCreditFacilityCovenantComplianceDebtUtilizationTriggeringLeverageRatioCompliancePercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mgni_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccountsPayableAndAccruedLiabilities" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccountsPayableAndAccruedLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour" abstract="false" name="LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_LineOfCreditFacilityIncreaseInMaximumBorrowingCapacity" abstract="false" name="LineOfCreditFacilityIncreaseInMaximumBorrowingCapacity" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_PaymentsToAcquireBusinessesGrossElectedIncreaseAmount" abstract="false" name="PaymentsToAcquireBusinessesGrossElectedIncreaseAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_GrossRevenueMember" abstract="true" name="GrossRevenueMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_AmortizationOfDebtIssuanceCostsAbstract" abstract="true" name="AmortizationOfDebtIssuanceCostsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="mgni_PerformanceSharesGrantedApril2021Member" abstract="true" name="PerformanceSharesGrantedApril2021Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <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_AccountsPayableSellerCurrent" abstract="false" name="AccountsPayableSellerCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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_BusinessCombinationConsiderationTransferredBeforeWorkingCapitalAdjustments" abstract="false" name="BusinessCombinationConsiderationTransferredBeforeWorkingCapitalAdjustments" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_LineOfCreditFacilityCovenantComplianceLeverageRatioMaximum" abstract="false" name="LineOfCreditFacilityCovenantComplianceLeverageRatioMaximum" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="mgni_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour" abstract="false" name="FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_AmortizationOfDebtIssuanceCostsRemainderOfFiscalYear" abstract="false" name="AmortizationOfDebtIssuanceCostsRemainderOfFiscalYear" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsUnvestedAndVestedButDeferredNumber" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsUnvestedAndVestedButDeferredNumber" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="mgni_DebtInstrumentAnnualPrincipalPaymentPercentage" abstract="false" name="DebtInstrumentAnnualPrincipalPaymentPercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mgni_A2014EmployeeStockPurchasePlanMember" abstract="true" name="A2014EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_RestructuringReserveAndMergerRelatedCostsSettledWithoutCash" abstract="false" name="RestructuringReserveAndMergerRelatedCostsSettledWithoutCash" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" 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-types:percentItemType"/>
  <xs:element id="mgni_CompanyOfficeSanFranciscoCAMember" abstract="true" name="CompanyOfficeSanFranciscoCAMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_SpotXIncMember" abstract="true" name="SpotXIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_ConversionTermIiMember" abstract="true" name="ConversionTermIiMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedButDeferredNumber" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedButDeferredNumber" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="mgni_NumberOfTranches" abstract="false" name="NumberOfTranches" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="mgni_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedAndVestedButDeferredWeightedAverageGrantDateFairValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedAndVestedButDeferredWeightedAverageGrantDateFairValue" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="mgni_LeaseRelatedLossContractsMember" abstract="true" name="LeaseRelatedLossContractsMember" 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-types:domainItemType"/>
  <xs:element id="mgni_SpotXAcquisitionSpringServeAcquisitionAndTelariaMergerMember" abstract="true" name="SpotXAcquisitionSpringServeAcquisitionAndTelariaMergerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_APICShareBasedPaymentArrangementDecreaseForCappedCalls" abstract="false" name="APICShareBasedPaymentArrangementDecreaseForCappedCalls" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_AccountsReceivableAllowanceForCreditLossMergerAssumed" abstract="false" name="AccountsReceivableAllowanceForCreditLossMergerAssumed" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_PerformanceSharesGrantedAugust2021Member" abstract="true" name="PerformanceSharesGrantedAugust2021Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgni_AmortizationOfDebtIssuanceCostsYearTwo" abstract="false" name="AmortizationOfDebtIssuanceCostsYearTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgni_ConversionTermIMember" abstract="true" name="ConversionTermIMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
