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.

Source: https://letsencrypt.org/stats/ as of February 14, 2018

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. And, with the help of EFF’s Certbot client and a range of other automation tools, it’s easy for webmasters of varying skill and resource levels to get a certificate and implement HTTPS. In fact, HTTPS encryption has become an automatic part of many hosting providers’ offerings.

50 million active certificates represents the number of certificates that are currently valid and have not expired. (Sometimes we also talk about “total issuance,” which refers to the total number of certificates ever issued by Let’s Encrypt. That number is around 217 million now.) Relating these numbers to names of “websites” is a bit complicated. Some certificates, such as those issued by certain hosting providers, cover many different sites. Yet some certificates are also redundant with others, so there may be a handful of active certificates all covering precisely the same names.

Every website protected is one step closer to encrypting the entire web, and milestones like this remind us that we are on our way to achieving that goal together.

One way to count is by “fully qualified domains active”—in other words, different names covered by non-expired certificates. This is now at 66 million. This metric can overcount sites; while most people would say that eff.org and www.eff.org are the same website, they count as two different names here.

Another way to count the number of websites that Let’s Encrypt protects is by looking at “registered domains active,” of which Let’s Encrypt currently has about 26 million. This refers to the number of different top-level domain names among non-expired certificates. In this case, supporters.eff.org and www.eff.org would be counted as one name. In cases where pages under the same top-level domain are run by different people with different content, this metric may undercount different sites.

No matter how you slice it, Let’s Encrypt is one of the largest CAs. And it has grown largely by giving websites their first-ever certificate rather than by grabbing websites from other CAs. That means that, as Let’s Encrypt grows, the number of HTTPS-protected websites on the web tends to grow too. Every website protected is one step closer to encrypting the entire web, and milestones like this remind us that we are on our way to achieving that goal together.