WebPKI Observatory — Market Share
Internet Security Research Group commands 40.1% of certificate issuance, nearly 2.5 times larger than second-place Google Trust Services at 16.2%. The top five CAs control 93.8% of all issuance, yet the trust ecosystem includes 96 trusted certificate authorities. This extreme concentration means that operational failures at ISRG or GTS would affect a majority of encrypted web traffic globally, while 82 tail CAs collectively issue just 6.2% of certificates.