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        <link:definition>2442422 - Disclosure - 401(k) Plan - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
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  <xs:element id="pubm_TemporaryEquityCommonStockSharesIssued" abstract="false" name="TemporaryEquityCommonStockSharesIssued" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="pubm_ReallocationOfNetIncomeLossAttributableToCommonStockholders" abstract="false" name="ReallocationOfNetIncomeLossAttributableToCommonStockholders" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_ShareBasedPaymentArrangementExpenseNet" abstract="false" name="ShareBasedPaymentArrangementExpenseNet" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_LineOfCreditFacilityBorrowingCapacityUnusedCapacityFeeClosingBalanceThreshold" abstract="false" name="LineOfCreditFacilityBorrowingCapacityUnusedCapacityFeeClosingBalanceThreshold" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_RedeemableCommonStockMember" abstract="true" name="RedeemableCommonStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="pubm_DebtInstrumentCovenantQuickRatioMinimum" abstract="false" name="DebtInstrumentCovenantQuickRatioMinimum" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="pubm_LineOfCreditFacilityBorrowingCapacityPercentageOfEligibleAccountsReceivableNet" abstract="false" name="LineOfCreditFacilityBorrowingCapacityPercentageOfEligibleAccountsReceivableNet" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="num:percentItemType"/>
  <xs:element id="pubm_BuyerThreeMember" abstract="true" name="BuyerThreeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="pubm_TwoPointFourTwoPercentPromissoryNotesDueAugust2021Member" abstract="true" name="TwoPointFourTwoPercentPromissoryNotesDueAugust2021Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="pubm_PropertyAndEquipmentIncludedInAccountsPayableAndAccruedExpenses" abstract="false" name="PropertyAndEquipmentIncludedInAccountsPayableAndAccruedExpenses" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_IncrementalCommonSharesAttributableToDilutiveEffectOfCallOptions" abstract="false" name="IncrementalCommonSharesAttributableToDilutiveEffectOfCallOptions" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="pubm_RestOfTheWorldMember" abstract="true" name="RestOfTheWorldMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="pubm_IncrementalCommonSharesAttributableToEmployeeStockPurchasePlan" abstract="false" name="IncrementalCommonSharesAttributableToEmployeeStockPurchasePlan" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="pubm_OnePublisherMember" abstract="true" name="OnePublisherMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
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  <xs:element id="pubm_BuyerOneMember" abstract="true" name="BuyerOneMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="pubm_ShareBasedPaymentArrangementTaxBenefit" abstract="false" name="ShareBasedPaymentArrangementTaxBenefit" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_StockBasedCompensationCapitalizedAsInternalUseSoftwareCosts" abstract="false" name="StockBasedCompensationCapitalizedAsInternalUseSoftwareCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="pubm_SiliconValleyBankMember" abstract="true" name="SiliconValleyBankMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="pubm_IncrementalCommonSharesAttributableToRestrictedStock" abstract="false" name="IncrementalCommonSharesAttributableToRestrictedStock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="pubm_BuyerTwoMember" abstract="true" name="BuyerTwoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
  <xs:element id="pubm_BuyerFourMember" abstract="true" name="BuyerFourMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="nonnum:domainItemType"/>
</xs:schema>
