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        <issuerAddress>
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          <com:city>WASHINGTON</com:city>
          <com:stateOrCountry>DC</com:stateOrCountry>
          <com:zipCode>20037</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>2022954200</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>SCHAEFFER DAVE</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>FOUNDER &amp; CEO</relationshipToIssuer>
        </relationshipsToIssuer>
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      <securitiesInformation>
        <securitiesClassTitle>COMMON</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>RBC CAPITAL MARKETS LLC </name>
          <address>
            <com:street1>250 NICOLLET MALL, SUITE 1700</com:street1>
            <com:city>MINNEAPOLIS</com:city>
            <com:stateOrCountry>MN</com:stateOrCountry>
            <com:zipCode>55401</com:zipCode>
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        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>30000</noOfUnitsSold>
        <aggregateMarketValue>1514016.00</aggregateMarketValue>
        <noOfUnitsOutstanding>49337310</noOfUnitsOutstanding>
        <approxSaleDate>05/14/2025</approxSaleDate>
        <securitiesExchangeName>NASDAQ</securitiesExchangeName>
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        <securitiesClassTitle>COMMON</securitiesClassTitle>
        <acquiredDate>04/30/2009</acquiredDate>
        <natureOfAcquisitionTransaction>VESTED RSU'S</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>30000</amountOfSecuritiesAcquired>
        <paymentDate>04/30/2009</paymentDate>
        <natureOfPayment>COMPENSATION</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
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          <name>DAVID SCHAEFFER C/O COGENT COMMUNICATIONS HOLDINGS INC</name>
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            <com:city>WASHINGTON</com:city>
            <com:stateOrCountry>DC</com:stateOrCountry>
            <com:zipCode>20037</com:zipCode>
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        <securitiesClassTitle>COGENT COMMUNICATIONS HOLDINGS INC</securitiesClassTitle>
        <saleDate>03/04/2025</saleDate>
        <amountOfSecuritiesSold>60000</amountOfSecuritiesSold>
        <grossProceeds>4302858.00</grossProceeds>
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        <sellerDetails>
          <name>DAVID SCHAEFFER C/O COGENT COMMUNICATIONS HOLDINGS INC</name>
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            <com:city>WASHINGTON</com:city>
            <com:stateOrCountry>DC</com:stateOrCountry>
            <com:zipCode>20037</com:zipCode>
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        <securitiesClassTitle>COGENT COMMUNICATIONS HOLDINGS INC</securitiesClassTitle>
        <saleDate>03/14/2025</saleDate>
        <amountOfSecuritiesSold>52500</amountOfSecuritiesSold>
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            <com:zipCode>20037</com:zipCode>
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        <securitiesClassTitle>COGENT COMMUNICATIONS HOLDINGS INC </securitiesClassTitle>
        <saleDate>05/12/2025</saleDate>
        <amountOfSecuritiesSold>11372</amountOfSecuritiesSold>
        <grossProceeds>569789.00</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>DAVID SCHAEFFER C/O COGENT COMMUNICATIONS HOLDINGS INC</name>
          <address>
            <com:street1>2450 N STREET NW</com:street1>
            <com:city>WASHINGTON </com:city>
            <com:stateOrCountry>DC</com:stateOrCountry>
            <com:zipCode>20037</com:zipCode>
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        </sellerDetails>
        <securitiesClassTitle>COGENT COMMUNICATIONS HOLDINGS INC</securitiesClassTitle>
        <saleDate>05/13/2025</saleDate>
        <amountOfSecuritiesSold>42628</amountOfSecuritiesSold>
        <grossProceeds>2150441.00</grossProceeds>
      </securitiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>05/14/2025</noticeDate>
        <signature>POA / JEFFREY EISCHENS</signature>
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text: 144
  0001166976
  XXXXXXXX
  LIVE
  0001158324
  COGENT COMMUNICATIONS HOLDINGS, INC.
  000-51829
  2450 N STREET, NW
  WASHINGTON
  DC
  20037
  2022954200
  SCHAEFFER DAVE
  FOUNDER & CEO
  COMMON
  RBC CAPITAL MARKETS LLC
  250 NICOLLET MALL, SUITE 1700
  MINNEAPOLIS
  MN
  55401
  30000
  1514016.00
  49337310
  05/14/2025
  NASDAQ
  COMMON
  04/30/2009
  VESTED RSU'S
  ISSUER
  N
  30000
  04/30/2009
  COMPENSATION
  N
  DAVID SCHAEFFER C/O COGENT COMMUNICATIONS HOLDINGS INC
  2450 N STREET NW
  WASHINGTON
  DC
  20037
  COGENT COMMUNICATIONS HOLDINGS INC
  03/04/2025
  60000
  4302858.00
  DAVID SCHAEFFER C/O COGENT COMMUNICATIONS HOLDINGS INC
  2450 N STREET NW
  WASHINGTON
  DC
  20037
  COGENT COMMUNICATIONS HOLDINGS INC
  03/14/2025
  52500
  3585298.00
  DAVID SCHAEFFER C/O COGENT COMMUNICATIONS HOLDINGS INC
  2450 N STREET NW
  WASHINGTON
  DC
  20037
  COGENT COMMUNICATIONS HOLDINGS INC
  05/12/2025
  11372
  569789.00
  DAVID SCHAEFFER C/O COGENT COMMUNICATIONS HOLDINGS INC
  2450 N STREET NW
  WASHINGTON
  DC
  20037
  COGENT COMMUNICATIONS HOLDINGS INC
  05/13/2025
  42628
  2150441.00
  05/14/2025
  POA / JEFFREY EISCHENS