WebPKI Observatory — Market Share
Five CAs control 93% of certificate issuance, with Internet Security Research Group leading at 39.2%, followed by Google Trust Services at 18.5% and DigiCert at 13.3%. The three-firm concentration ratio stands at 71.11%, while the Herfindahl-Hirschman Index of 2324 indicates moderate concentration by antitrust standards. Despite 90 trusted CAs in root stores, the remaining 76 tail CAs collectively represent less than 7% of the market, creating a stark division between dominant operators and marginalized participants.