The tremendous deployment of HTTPS in recent years has been a wonderful achievement for the Internet, and Let’s Encrypt has made a far-reaching contribution to the effort.
This evening, the Let’s Encrypt certificate authority issued its hundred millionth digital certificate. This is a remarkable milestone in just a year and a half of public operation; Let’s Encrypt is likely now either the largest or second-largest public CA by volume of certificates issued.
Free certificates from Let’s Encrypt allow web sites to offer secure HTTPS connections to their users, protecting the privacy and security of those connections against many network-based threats. EFF continues to help develop the Boulder software that Let’s Encrypt uses internally, as well as Certbot, Let’s Encrypt’s recommended software for obtaining and installing certificates on web servers.
For various reasons, the hundred-million mark does not mean that a hundred million different sites use Let’s Encrypt certificates1. The number of web sites protected by Let’s Encrypt is probably between 17 million and 46 million, depending on what definition of a “web site” we use2. It’s hard to say with certainty whether Let’s Encrypt has issued the largest number of certificates because CAs are not currently required to disclose the certificates they issue, but Let’s Encrypt does so voluntarily. And the number of sites protected by Let’s Encrypt will continue to grow rapidly as more and more hosting providers and server software offer convenient Let’s Encrypt support to help bring HTTPS to sites that didn’t have it before.