In yet another milestone on the path to encrypting the web, Let’s Encrypt has now issued over 50 million active certificates. Depending on your definition of “website,” this suggests that Let’s Encrypt is protecting between about 23 million and 66 million websites with HTTPS (more on that below). Whatever the number, it’s growing every day as more and more webmasters and hosting providers use Let’s Encrypt to provide HTTPS on their websites by default.
Let’s Encrypt is a certificate authority, or CA. CAs like Let’s Encrypt are crucial to secure, HTTPS-encrypted browsing. They issue and maintain digital certificates that help web users and their browsers know they’re actually talking to the site they intended to.
One of the things that sets Let’s Encrypt apart is that it issues these certificates for free.
Read more at the EFF