Is Let’s Encrypt a Largest Certificate Authority on a Web?

By a time we review this, Let’s Encrypt will have expelled a 12 millionth certificate, of that 6 million are active and unexpired. With these milestones, Let’s Encrypt now appears to us to be a a Internet’s largest certificate authority—but a recent analysis by W3Techs pronounced we were usually a third largest. So in this post we investigate: how vast is Let’s Encrypt, really?

What are certificate authorities, and how do we magnitude their size?

Certificate authorities (CAs) emanate and contend digital certificates that assistance web users and their browsers know they’re indeed articulate to a site they dictated to. This is essential to secure, HTTPS-encrypted communication, as these certificates determine a organisation between an HTTPS site and a crypographic open key. A CA provides a owners of a website with a sealed certificate that web visitors can exclusively verify. The certificate tells a user’s browser software, “If we use this pivotal to set adult secure communications with this website, no one can prevent those communications.” Without such an introduction, browsers can stoop to trade interception, alteration and eavesdropping; even if they used encryption, they wouldn’t be certain if they were articulate directly to a site as against to a man-in-the-middle attacker.1

Let’s Encrypt is a free, automated, open CA founded by EFF, Mozilla, and a University of Michigan, with Cisco and Akamai as first sponsors. But is it a largest CA? It turns out this could meant several things: arising a many open certificates, arising a many active open certificates, safeguarding a many Internet connectors or sites, or any of a horde of other probable metrics. In this post we’ll travel by a integrate of ways to magnitude this, and a stipulations and caveats that comes with those measurements.

The numbers

At present, Let’s Encrypt has expelled 6 million unexpired certificates for possibly 4 or 10 million domains, depending on how we count.

Source: JC Jones

On this chart, “certificates active,” in orange, represents a series of certificates that have been expelled and are not nonetheless expired. 2

Some of these un-expired certificates are duplicates, with some-more than one certificate covering one domain name. Others are a opposite, covering many domain names underneath one certificate.3 So it’s substantially some-more accurate to demeanour during a series of graphic domains lonesome by unexpired certs. “Fully-qualified domains active” in red shows a series of opposite names among non-expired certificates. For example, and are treated as dual opposite names. This metric can overcount sites; while many people would contend that and are a same website, they count as dual opposite names here.

Finally, “Registered domains active” in green depends a series of opposite top-level domain names among non-expired certificates. In this case, and would be counted as one name. This metric might undercount opposite sites, since pages underneath a same top-level domain still might be run by opposite people with opposite content—for example, opposite WordPress blogs hosted underneath

Counting by series of certs: 3rd largest, or largest?

Our friends during W3Techs Web Technology Surveys recently expelled a blog post examining a CA marketplace and putting Let’s Encrypt in third place among certificate providers.

When we looked closely during these numbers, however, we found that W3Techs was not looking during a whole certificate market; a research took into account usually a tip 10,000,000 many renouned websites (as ranked by Alexa). This is critical since Let’s Encrypt (below shown as “IdenTrust,” since of a base Let’s Encrypt uses) is ordinarily used by smaller, reduction popular, low-traffic sites rather than big, renouned ones. For that reason, W3Tech’s third-place ranking that relied on a biggest, many renouned sites on a web enormously undercounted Let’s Encrypt’s altogether marketplace share. The smaller sites that we essentially offer are accurately a sites that W3Techs (and other analyses of tip Alexa-ranked sites) are slightest expected to count.

CAs in a reduce partial of a graph tend to offer some-more low-traffic sites. Source: W3Techs.

By other metrics, Let’s Encrypt is in fact a CA that has expelled a many certificates and stable a many sites. This ranking from a Censys plan looks during all famous certificates that are valid, unexpired, and would be supposed by browsers during a impulse of a query:


But this first-place ranking requires some caveats. The rankings above embody information from Certificate Transparency, an open-source bid to guard and review TLS/SSL certificates. This information might embody certificates that were never deployed in use or are no longer actively in use. So, if someone gets a Let’s Encrypt certificate yet afterwards doesn’t indeed use it, it still contributes to Let’s Encrypt’s first-place mark in a draft above.

This dataset might also embody duplicates. For example, a webmaster new to TLS/SSL certificates might incidentally run a Let’s Encrypt patron like Certbot 5 times in a quarrel and get a same certificate each time. This will uncover adult in a draft above as 5 opposite certificates, even yet that webmaster is substantially usually regulating one. Of course, this is counteracted by a fact that many other certificates cover mixed domains during once.

Lastly, there are categories of certificates that aren’t being counted here. This ranking covers usually publicly devoted certificates (as against to self-signed ones, or those sealed by private CAs not devoted by browsers by default) for domain names (as against to, for example, S/MIME certificates for email addresses, of that there are a outrageous and mostly unrestrained number).

Valuable contributions regardless of numbers

The biggest caveats in a dual rankings above—whether a dataset takes into comment reduction renouned sites (which creates a W3Techs numbers unequivocally desperate about Let’s Encrypt), and a probability of new or transcribe certificates (which might make a possess numbers optimistic)—illustrate Let’s Encrypt’s profitable contributions to encryption efforts regardless of numbers or rankings.

As a disproportion between a dual datasets shows, Let’s Encrypt has been adopted some-more by smaller sites than by incomparable ones—often personal blogs or by a sites of tiny businesses and associations. That means that, compared to other CAs, we strengthen fewer of a many famous and many renouned Internet sites, and apparently also a smaller fragment of all web browsing activity. But that’s excellent by us.

One of a ways Let’s Encrypt has been assisting to secure a web is by creation it easy and affordable for sites that have never had certs before to spin on secure HTTPS connections, and for program systems to start enabling HTTPS automatically and by default. Our giveaway certificates might be some-more expected to be left new than costly certificates, and reduction consultant webmasters might incidentally transcribe certificates—but that’s partial of creation HTTPS formation accessible to some-more webmasters opposite a operation of apparatus and ability levels. Statistics advise that many of a expansion has come not during a responsibility of other CAs, yet from giving formerly unencrypted sites their first-ever certificates.

Rankings also destroy to constraint a communities that a CA like Let’s Encrypt can serve. A vast share of Let’s Encrypt certificates have been expelled to vital hosting companies and platforms, including: Automattic, a web growth house behind; Shopify, an e-commerce platform; and OVH, a European ISP. And they are not alone. Dozens of web hosting providers and companies have done a joining to use Let’s Encrypt to automatically strengthen their patron sites with HTTPS.

We are committed to ancillary some-more companies and communities who wish to make this move. Learn some-more about Let’s Encrypt and how to use a web’s largest CA here.

  • 1. Note that certificates don’t unequivocally solve a associated authentication nonplus of meaningful that you’re visiting a right domain name and are not being phished, that is in many ways a harder problem.
  • 2. Although it is not shown on this chart, a count of all certificates ever issued, including lapsed certs, is about 12 million.
  • 3. Let’s Encrypt supports adult to one hundred domains per certificate.