144 0001166976 XXXXXXXX LIVE 0001158324 Cogent Communications Holdings, Inc. 000-51829 2450 N. Street N.W. Washington DC 20037 202-295-4200 David Schaeffer Founder CEO Common Stock J.P. Morgan Securities LLC

390 Madison Avenue, 6th Floor New York NY 10017

25000 1151250 49337310 05/22/2025 NASDAQ Common Stock 04/30/2009 Vested restricted stock grant Issuer N 25000 04/30/2009 Compensation N David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 03/04/2025 60000 4302858 David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 03/14/2025 52500 3585299 David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 05/12/2025 11372 569206 David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 05/13/2025 42628 2147884 David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 05/14/2025 30000 1519146 David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 05/15/2025 40000 2013036 David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 05/16/2025 15000 764934 David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 05/20/2025 15000 748448 David Schaeffer

C/o Cogent Communications Holdings Inc 2450 N. Street N.W. Washington DC 20037

Common Stock 05/21/2025 40000 1871449 05/22/2025 /s/ J.P. Morgan Securities LLC as agent and attorney-in-fact for David Schaeffer