<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:d78808fe-f8ac-4516-a752-9a6300d7fc13,g:b02f08f5-50be-472b-b593-575bdbc5af43-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:ontf="http://www.on24.com/20220630" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.on24.com/20220630">
  <xs:import namespace="http://fasb.org/srt/2021-01-31" schemaLocation="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2021-01-31" schemaLocation="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd"/>
  <xs:import namespace="http://www.w3.org/1999/xlink" schemaLocation="http://www.xbrl.org/2003/xlink-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/country/2021" schemaLocation="https://xbrl.sec.gov/country/2021/country-2021.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2021q4" schemaLocation="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ontf-20220630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ontf-20220630_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ontf-20220630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ontf-20220630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Cover" roleURI="http://www.on24.com/role/Cover">
        <link:definition>0001001 - Document - Cover</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheets" roleURI="http://www.on24.com/role/CondensedConsolidatedBalanceSheets">
        <link:definition>1001002 - Statement - Condensed Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheetsParenthetical" roleURI="http://www.on24.com/role/CondensedConsolidatedBalanceSheetsParenthetical">
        <link:definition>1002003 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofOperations" roleURI="http://www.on24.com/role/CondensedConsolidatedStatementsofOperations">
        <link:definition>1003004 - Statement - Condensed Consolidated Statements of Operations</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofComprehensiveLoss" roleURI="http://www.on24.com/role/CondensedConsolidatedStatementsofComprehensiveLoss">
        <link:definition>1004005 - Statement - Condensed Consolidated Statements of Comprehensive Loss</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofConvertiblePreferredStockandStockholdersEquityDeficit" roleURI="http://www.on24.com/role/CondensedConsolidatedStatementsofConvertiblePreferredStockandStockholdersEquityDeficit">
        <link:definition>1005006 - Statement - Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofCashFlows" roleURI="http://www.on24.com/role/CondensedConsolidatedStatementsofCashFlows">
        <link:definition>1006007 - Statement - Condensed Consolidated Statements of Cash Flows</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DescriptionofBusinessandSignificantAccountingPolicies" roleURI="http://www.on24.com/role/DescriptionofBusinessandSignificantAccountingPolicies">
        <link:definition>2101101 - Disclosure - Description of Business and Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DescriptionofBusinessandSignificantAccountingPoliciesPolicies" roleURI="http://www.on24.com/role/DescriptionofBusinessandSignificantAccountingPoliciesPolicies">
        <link:definition>2202201 - Disclosure - Description of Business and Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DescriptionofBusinessandSignificantAccountingPoliciesAdditionalInformationDetails" roleURI="http://www.on24.com/role/DescriptionofBusinessandSignificantAccountingPoliciesAdditionalInformationDetails">
        <link:definition>2403401 - Disclosure - Description of Business and Significant Accounting Policies - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Revenue" roleURI="http://www.on24.com/role/Revenue">
        <link:definition>2104102 - Disclosure - Revenue</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueTables" roleURI="http://www.on24.com/role/RevenueTables">
        <link:definition>2305301 - Disclosure - Revenue (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueScheduleofDisaggregationofRevenuebyGeographicRegionDetails" roleURI="http://www.on24.com/role/RevenueScheduleofDisaggregationofRevenuebyGeographicRegionDetails">
        <link:definition>2406402 - Disclosure - Revenue - Schedule of Disaggregation of Revenue by Geographic Region (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueForeignCountriesWhichContributed10ormoreofTotalRevenueDetail" roleURI="http://www.on24.com/role/RevenueForeignCountriesWhichContributed10ormoreofTotalRevenueDetail">
        <link:definition>2407403 - Disclosure - Revenue - Foreign Countries Which Contributed 10% or more of Total Revenue (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueContractBalancesandCostsToObtainAContractDetails" roleURI="http://www.on24.com/role/RevenueContractBalancesandCostsToObtainAContractDetails">
        <link:definition>2408404 - Disclosure - Revenue - Contract Balances and Costs To Obtain A Contract (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueRemainingPerformanceObligationsDetails" roleURI="http://www.on24.com/role/RevenueRemainingPerformanceObligationsDetails">
        <link:definition>2409405 - Disclosure - Revenue - Remaining Performance Obligations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueRemainingPerformanceObligationsDetails_1" roleURI="http://www.on24.com/role/RevenueRemainingPerformanceObligationsDetails_1">
        <link:definition>2409405 - Disclosure - Revenue - Remaining Performance Obligations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecurities" roleURI="http://www.on24.com/role/MarketableSecurities">
        <link:definition>2110103 - Disclosure - Marketable Securities</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesTables" roleURI="http://www.on24.com/role/MarketableSecuritiesTables">
        <link:definition>2311302 - Disclosure - Marketable Securities (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesSummaryofMarketableSecuritiesDetails" roleURI="http://www.on24.com/role/MarketableSecuritiesSummaryofMarketableSecuritiesDetails">
        <link:definition>2412406 - Disclosure - Marketable Securities - Summary of Marketable Securities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesMarketableSecuritiesinanUnrealizedLossPositionDetails" roleURI="http://www.on24.com/role/MarketableSecuritiesMarketableSecuritiesinanUnrealizedLossPositionDetails">
        <link:definition>2413407 - Disclosure - Marketable Securities - Marketable Securities in an Unrealized Loss Position (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesAdditionalInformationDetails" roleURI="http://www.on24.com/role/MarketableSecuritiesAdditionalInformationDetails">
        <link:definition>2414408 - Disclosure - Marketable Securities - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesSummaryofRemainingContractualMaturitiesofMarketableSecuritiesDetails" roleURI="http://www.on24.com/role/MarketableSecuritiesSummaryofRemainingContractualMaturitiesofMarketableSecuritiesDetails">
        <link:definition>2415409 - Disclosure - Marketable Securities - Summary of Remaining Contractual Maturities of Marketable Securities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurement" roleURI="http://www.on24.com/role/FairValueMeasurement">
        <link:definition>2116104 - Disclosure - Fair Value Measurement</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementTables" roleURI="http://www.on24.com/role/FairValueMeasurementTables">
        <link:definition>2317303 - Disclosure - Fair Value Measurement (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementSummaryofFinancialInstrumentsRecordedatFairValueonRecurringBasisDetails" roleURI="http://www.on24.com/role/FairValueMeasurementSummaryofFinancialInstrumentsRecordedatFairValueonRecurringBasisDetails">
        <link:definition>2418410 - Disclosure - Fair Value Measurement - Summary of Financial Instruments Recorded at Fair Value on Recurring Basis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetsComponents" roleURI="http://www.on24.com/role/BalanceSheetsComponents">
        <link:definition>2119105 - Disclosure - Balance Sheets Components</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetsComponentsTables" roleURI="http://www.on24.com/role/BalanceSheetsComponentsTables">
        <link:definition>2320304 - Disclosure - Balance Sheets Components (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetsComponentsSummaryofPrepaidExpensesandOtherCurrentAssetsDetails" roleURI="http://www.on24.com/role/BalanceSheetsComponentsSummaryofPrepaidExpensesandOtherCurrentAssetsDetails">
        <link:definition>2421411 - Disclosure - Balance Sheets Components - Summary of Prepaid Expenses and Other Current Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetsComponentsSummaryofPropertyandEquipmentNetDetails" roleURI="http://www.on24.com/role/BalanceSheetsComponentsSummaryofPropertyandEquipmentNetDetails">
        <link:definition>2422412 - Disclosure - Balance Sheets Components - Summary of Property and Equipment, Net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetsComponentsAdditionalInformationDetails" roleURI="http://www.on24.com/role/BalanceSheetsComponentsAdditionalInformationDetails">
        <link:definition>2423413 - Disclosure - Balance Sheets Components - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetsComponentsScheduleofPropertyandEquipmentNetofDepreciationandAmortizationbyGeographicRegionDetails" roleURI="http://www.on24.com/role/BalanceSheetsComponentsScheduleofPropertyandEquipmentNetofDepreciationandAmortizationbyGeographicRegionDetails">
        <link:definition>2424414 - Disclosure - Balance Sheets Components - Schedule of Property and Equipment, Net of Depreciation and Amortization, by Geographic Region (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetsComponentsSummaryofAccruedandOtherCurrentLiabilitiesDetails" roleURI="http://www.on24.com/role/BalanceSheetsComponentsSummaryofAccruedandOtherCurrentLiabilitiesDetails">
        <link:definition>2425415 - Disclosure - Balance Sheets Components - Summary of Accrued and Other Current Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BalanceSheetsComponentsSummaryofOtherLongTermLiabilitiesDetails" roleURI="http://www.on24.com/role/BalanceSheetsComponentsSummaryofOtherLongTermLiabilitiesDetails">
        <link:definition>2426416 - Disclosure - Balance Sheets Components - Summary of Other Long-Term Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombination" roleURI="http://www.on24.com/role/BusinessCombination">
        <link:definition>2127106 - Disclosure - Business Combination</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessCombinationDetails" roleURI="http://www.on24.com/role/BusinessCombinationDetails">
        <link:definition>2428417 - Disclosure - Business Combination (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssets" roleURI="http://www.on24.com/role/IntangibleAssets">
        <link:definition>2129107 - Disclosure - Intangible Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssetsTables" roleURI="http://www.on24.com/role/IntangibleAssetsTables">
        <link:definition>2330305 - Disclosure - Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssetsAcquiredIntangibleAssetsDetails" roleURI="http://www.on24.com/role/IntangibleAssetsAcquiredIntangibleAssetsDetails">
        <link:definition>2431418 - Disclosure - Intangible Assets - Acquired Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssetsAcquiredIntangibleAssetsDetails_1" roleURI="http://www.on24.com/role/IntangibleAssetsAcquiredIntangibleAssetsDetails_1">
        <link:definition>2431418 - Disclosure - Intangible Assets - Acquired Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssetsAdditionalInformationDetails" roleURI="http://www.on24.com/role/IntangibleAssetsAdditionalInformationDetails">
        <link:definition>2432419 - Disclosure - Intangible Assets - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssetsFutureAmortizationExpenseDetails" roleURI="http://www.on24.com/role/IntangibleAssetsFutureAmortizationExpenseDetails">
        <link:definition>2433420 - Disclosure - Intangible Assets - Future Amortization Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Leases" roleURI="http://www.on24.com/role/Leases">
        <link:definition>2134108 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesTables" roleURI="http://www.on24.com/role/LeasesTables">
        <link:definition>2335306 - Disclosure - Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesAdditionalInformationDetails" roleURI="http://www.on24.com/role/LeasesAdditionalInformationDetails">
        <link:definition>2436421 - Disclosure - Leases - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesBalanceSheetClassificationDetails" roleURI="http://www.on24.com/role/LeasesBalanceSheetClassificationDetails">
        <link:definition>2437422 - Disclosure - Leases - Balance Sheet Classification (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesLeaseCostDetails" roleURI="http://www.on24.com/role/LeasesLeaseCostDetails">
        <link:definition>2438423 - Disclosure - Leases - Lease Cost (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesMaturityofLeaseLiabilitiesDetails" roleURI="http://www.on24.com/role/LeasesMaturityofLeaseLiabilitiesDetails">
        <link:definition>2439424 - Disclosure - Leases - Maturity of Lease Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesMaturityofLeaseLiabilitiesDetails_1" roleURI="http://www.on24.com/role/LeasesMaturityofLeaseLiabilitiesDetails_1">
        <link:definition>2439424 - Disclosure - Leases - Maturity of Lease Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesMaturityofLeaseLiabilitiesUnderASC840Details" roleURI="http://www.on24.com/role/LeasesMaturityofLeaseLiabilitiesUnderASC840Details">
        <link:definition>2440425 - Disclosure - Leases - Maturity of Lease Liabilities Under ASC 840 (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesWeightedAverageLeaseTermDetails" roleURI="http://www.on24.com/role/LeasesWeightedAverageLeaseTermDetails">
        <link:definition>2441426 - Disclosure - Leases - Weighted-Average Lease Term (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSupplementalCashFlowsDetails" roleURI="http://www.on24.com/role/LeasesSupplementalCashFlowsDetails">
        <link:definition>2442427 - Disclosure - Leases - Supplemental Cash Flows (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CreditFacility" roleURI="http://www.on24.com/role/CreditFacility">
        <link:definition>2143109 - Disclosure - Credit Facility</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CreditFacilityRevolvingLineofCreditDetails" roleURI="http://www.on24.com/role/CreditFacilityRevolvingLineofCreditDetails">
        <link:definition>2444428 - Disclosure - Credit Facility- Revolving Line of Credit (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentandContingencies" roleURI="http://www.on24.com/role/CommitmentandContingencies">
        <link:definition>2145110 - Disclosure - Commitment and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentandContingenciesPurchaseObligationsDetails" roleURI="http://www.on24.com/role/CommitmentandContingenciesPurchaseObligationsDetails">
        <link:definition>2446429 - Disclosure - Commitment and Contingencies - Purchase Obligations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentandContingenciesContingenciesandLegalProceedingsDetails" roleURI="http://www.on24.com/role/CommitmentandContingenciesContingenciesandLegalProceedingsDetails">
        <link:definition>2447430 - Disclosure - Commitment and Contingencies - Contingencies and Legal Proceedings (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlan" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlan">
        <link:definition>2148111 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanTables" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanTables">
        <link:definition>2349307 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan - (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanPreferredStockDetails" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanPreferredStockDetails">
        <link:definition>2450431 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan - Preferred Stock (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanCommonStockDetails" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanCommonStockDetails">
        <link:definition>2451432 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan- Common Stock (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanCommonStockReservedforFutureIssuanceDetails" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanCommonStockReservedforFutureIssuanceDetails">
        <link:definition>2452433 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan - Common Stock Reserved for Future Issuance (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanSummaryofStockOptionsDetails" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanSummaryofStockOptionsDetails">
        <link:definition>2453434 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan - Summary of Stock Options (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanSummaryofRSUActivityUnderEquityIncentivePlansandRelatedInformationDetails" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanSummaryofRSUActivityUnderEquityIncentivePlansandRelatedInformationDetails">
        <link:definition>2454435 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan- Summary of RSU Activity Under Equity Incentive Plans and Related Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanRestrictedStockUnitDetails" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanRestrictedStockUnitDetails">
        <link:definition>2455436 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan - Restricted Stock Unit (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanSummaryofSharebasedCompensationExpensebylineitemintheCondensedConsolidatedStatementsofOperationsDetail" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanSummaryofSharebasedCompensationExpensebylineitemintheCondensedConsolidatedStatementsofOperationsDetail">
        <link:definition>2456437 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan - Summary of Share-based Compensation Expense by line item in the Condensed Consolidated Statements of Operations (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanSummaryofUnrecognizedStockbasedCompensationExpenseDetails" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanSummaryofUnrecognizedStockbasedCompensationExpenseDetails">
        <link:definition>2457438 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan - Summary of Unrecognized Stock-based Compensation Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDeficitandEquityIncentivePlanRepurchaseofCommonStockDetails" roleURI="http://www.on24.com/role/StockholdersEquityDeficitandEquityIncentivePlanRepurchaseofCommonStockDetails">
        <link:definition>2458439 - Disclosure - Stockholders&#8217; Equity (Deficit) and Equity Incentive Plan - Repurchase of Common Stock (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxes" roleURI="http://www.on24.com/role/IncomeTaxes">
        <link:definition>2159112 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesTables" roleURI="http://www.on24.com/role/IncomeTaxesTables">
        <link:definition>2360308 - Disclosure - Income Taxes (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesProvisionforIncomeTaxesDetails" roleURI="http://www.on24.com/role/IncomeTaxesProvisionforIncomeTaxesDetails">
        <link:definition>2461440 - Disclosure - Income Taxes - Provision for Income Taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesAdditionalInformationDetails" roleURI="http://www.on24.com/role/IncomeTaxesAdditionalInformationDetails">
        <link:definition>2462441 - Disclosure - Income Taxes - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetLossPerShareAttributabletoCommonStockholders" roleURI="http://www.on24.com/role/NetLossPerShareAttributabletoCommonStockholders">
        <link:definition>2163113 - Disclosure - Net Loss Per Share Attributable to Common Stockholders</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetLossPerShareAttributabletoCommonStockholdersTables" roleURI="http://www.on24.com/role/NetLossPerShareAttributabletoCommonStockholdersTables">
        <link:definition>2364309 - Disclosure - Net Loss Per Share Attributable to Common Stockholders (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetLossPerShareAttributabletoCommonStockholdersScheduleofComputationofBasicandDilutedNetLossPerShareDetails" roleURI="http://www.on24.com/role/NetLossPerShareAttributabletoCommonStockholdersScheduleofComputationofBasicandDilutedNetLossPerShareDetails">
        <link:definition>2465442 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="NetLossPerShareAttributabletoCommonStockholdersScheduleofPotentialSharesofCommonStockExcludedfromComputationofDilutedNetLossPerShareDetails" roleURI="http://www.on24.com/role/NetLossPerShareAttributabletoCommonStockholdersScheduleofPotentialSharesofCommonStockExcludedfromComputationofDilutedNetLossPerShareDetails">
        <link:definition>2466443 - Disclosure - Net Loss Per Share Attributable to Common Stockholders - Schedule of Potential Shares of Common Stock Excluded from Computation of Diluted Net Loss Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RelatedPartyTransactions" roleURI="http://www.on24.com/role/RelatedPartyTransactions">
        <link:definition>2167114 - Disclosure - Related Party Transactions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RelatedPartyTransactionsAdditionalInformationDetails" roleURI="http://www.on24.com/role/RelatedPartyTransactionsAdditionalInformationDetails">
        <link:definition>2468444 - Disclosure - Related Party Transactions - Additional Information (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>
  </xs:annotation>
  <xs:element id="ontf_DescriptionOfBusinessAndSignificantAccountingPoliciesLineItems" abstract="true" name="DescriptionOfBusinessAndSignificantAccountingPoliciesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="ontf_LesseeTermOfContract" abstract="false" name="LesseeTermOfContract" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="ontf_AccountsReceivableBenchmarkMember" abstract="true" name="AccountsReceivableBenchmarkMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_RightOfUseAssetRecognizedUponAdoptionOfAccountingStandard" abstract="false" name="RightOfUseAssetRecognizedUponAdoptionOfAccountingStandard" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_LeaseRightOfUseAssetAbstract" abstract="true" name="LeaseRightOfUseAssetAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="ontf_ProfessionalServicesMember" abstract="true" name="ProfessionalServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_CommonStockNumberOfVotesPerShare" abstract="false" name="CommonStockNumberOfVotesPerShare" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="ontf_LeaseLiability" abstract="false" name="LeaseLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_AccruedBonusesAndSalesCommissionCurrent" abstract="false" name="AccruedBonusesAndSalesCommissionCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_ShareholderDerivativeComplaintMember" abstract="true" name="ShareholderDerivativeComplaintMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_FiniteLivedIntangibleAssetsEffectOfForeignCurrencyTranslationGross" abstract="false" name="FiniteLivedIntangibleAssetsEffectOfForeignCurrencyTranslationGross" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_RecurringRevenueTrailingPeriod" abstract="false" name="RecurringRevenueTrailingPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="ontf_FiniteLivedIntangibleAssetsAccumulatedAmortizationBeforeForeignCurrencyTranslation" abstract="false" name="FiniteLivedIntangibleAssetsAccumulatedAmortizationBeforeForeignCurrencyTranslation" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_LeaseLiabilityCurrentAbstract" abstract="true" name="LeaseLiabilityCurrentAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="ontf_CashPaidForAmountsIncludedInTheMeasurementOfLeaseLiabilitiesAbstract" abstract="true" name="CashPaidForAmountsIncludedInTheMeasurementOfLeaseLiabilitiesAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="ontf_PerformanceBasedRestrictedStockUnitsMember" abstract="true" name="PerformanceBasedRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_ConcentrationRiskNumberOfCustomersAccountingForMoreThanTenPercent" abstract="false" name="ConcentrationRiskNumberOfCustomersAccountingForMoreThanTenPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="ontf_LeaseRightOfUseAsset" abstract="false" name="LeaseRightOfUseAsset" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_WeightedAverageLeaseTermAndDiscountRateTableTextBlock" abstract="false" name="WeightedAverageLeaseTermAndDiscountRateTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="ontf_A2021EquityIncentivePlanMember" abstract="true" name="A2021EquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_ShareRepurchasesAveragePricePerShareIncludingCommissions" abstract="false" name="ShareRepurchasesAveragePricePerShareIncludingCommissions" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="ontf_SoftwareLicenseFeesAndCoLocationFacilitiesAndServicesMember" abstract="true" name="SoftwareLicenseFeesAndCoLocationFacilitiesAndServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_CashEquivalentsAndAvailableForSaleDebtSecuritiesFairValueDisclosure" abstract="false" name="CashEquivalentsAndAvailableForSaleDebtSecuritiesFairValueDisclosure" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_FiniteLivedIntangibleAssetsEffectOfForeignCurrencyTranslationNet" abstract="false" name="FiniteLivedIntangibleAssetsEffectOfForeignCurrencyTranslationNet" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_TwoThousandTwentyOneEmployeeStockPurchasePlanMember" abstract="true" name="TwoThousandTwentyOneEmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_ProvisionForAllowanceForDoubtfulAccountsAndBillingReserve" abstract="false" name="ProvisionForAllowanceForDoubtfulAccountsAndBillingReserve" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_OtherOfferingCosts" abstract="false" name="OtherOfferingCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_CustomersRepresentingConcentrationRiskMember" abstract="true" name="CustomersRepresentingConcentrationRiskMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_CreditCardSublimitMember" abstract="true" name="CreditCardSublimitMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_CommonStockReservedForFutureIssuanceTableTextBlock" abstract="false" name="CommonStockReservedForFutureIssuanceTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="ontf_CommonStockCapitalSharesReservedForFutureIssuanceNumberOfAdditionalSharesReserved" abstract="false" name="CommonStockCapitalSharesReservedForFutureIssuanceNumberOfAdditionalSharesReserved" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="ontf_NetIncomeLossAttributableToCommonStockholders" abstract="false" name="NetIncomeLossAttributableToCommonStockholders" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_RightOfUseAssetsObtainedInExchangeForLeaseObligationsAbstract" abstract="true" name="RightOfUseAssetsObtainedInExchangeForLeaseObligationsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="ontf_VibbioASMember" abstract="true" name="VibbioASMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_ForeignCurrencyTranslationMember" abstract="true" name="ForeignCurrencyTranslationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_FiniteLivedIntangibleAssetsNetBeforeForeignCurrencyTranslation" abstract="false" name="FiniteLivedIntangibleAssetsNetBeforeForeignCurrencyTranslation" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_OtherGeographicalAreaMember" abstract="true" name="OtherGeographicalAreaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_SubscriptionAndOtherPlatformMember" abstract="true" name="SubscriptionAndOtherPlatformMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_RevolvingCreditFacilityWithAtLeast100MillionDepositMember" abstract="true" name="RevolvingCreditFacilityWithAtLeast100MillionDepositMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_SalesAndUseTaxAssessmentMember" abstract="true" name="SalesAndUseTaxAssessmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_DescriptionOfBusinessAndSignificantAccountingPoliciesTable" abstract="true" name="DescriptionOfBusinessAndSignificantAccountingPoliciesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="ontf_AssetsAndLiabilitiesLesseeTableTextBlock" abstract="false" name="AssetsAndLiabilitiesLesseeTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="ontf_RevolvingCreditFacilityWithLessThan100MillionDepositMember" abstract="true" name="RevolvingCreditFacilityWithLessThan100MillionDepositMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_ComputerEquipmentsAndSoftwareMember" abstract="true" name="ComputerEquipmentsAndSoftwareMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_FiniteLivedIntangibleAssetsGrossBeforeForeignCurrencyTranslation" abstract="false" name="FiniteLivedIntangibleAssetsGrossBeforeForeignCurrencyTranslation" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_UndesignatedPreferredStockMember" abstract="true" name="UndesignatedPreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_PutativeClassActionsDouviaVON24AndGoemerVON24Member" abstract="true" name="PutativeClassActionsDouviaVON24AndGoemerVON24Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_LeaseLiabilityNoncurrentAbstract" abstract="true" name="LeaseLiabilityNoncurrentAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="ontf_MiscellaneousReceivables" abstract="false" name="MiscellaneousReceivables" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_ShortTermBorrowingAmountSubjectToMaximumDebtToEBITDARatioFinancialCovenant" abstract="false" name="ShortTermBorrowingAmountSubjectToMaximumDebtToEBITDARatioFinancialCovenant" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="ontf_BankDepositsMember" abstract="true" name="BankDepositsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="ontf_SupplementalCashFlowInformationTableTextBlock" abstract="false" name="SupplementalCashFlowInformationTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
</xs:schema>
