WebPKI Observatory — Market Share
Five CAs control 88% of all publicly trusted certificates, with ISRG leading at 32% share, followed by Google Trust Services at 21% and DigiCert at 18%. Market concentration measured by HHI stands at 1981, indicating a moderately concentrated market where a handful of players dominate while 74 tail CAs collectively issue the remaining volume. This structure creates systemic dependencies where operational failures at top providers would immediately affect a third of the encrypted web.