10 Years of Let's Encrypt

Summary

On September 14, 2015, our first publicly-trusted certificate went live. We were proud that we had issued a certificate that a significant majority of clients could accept, and had done it using automated software. Of course, in retrospect this was just the first of billions of certificates. Today, Let’s Encrypt is the largest certificate authority in the world in terms of certificates issued, the ACME protocol we helped create and standardize is integrated throughout the server ecosystem, and we’ve become a household name among system administrators. We’re closing in on protecting one billion web sites. In 2023, we marked the tenth anniversary of the creation of our nonprofit, Internet Security Research Group, which continues to host Let’s Encrypt and other public benefit infrastructure projects. Now, in honor of the tenth anniversary of Let’s Encrypt’s public certificate issuance and the start of the general availability of our services, we’re looking back at a few milestones and factors that contributed to our success. Growth A conspicuous part of Let’s Encrypt’s history is how thoroughly our vision of scalability through automation has succeeded. In March 2016, we issued our one millionth certificate. Just two years later, in September 2018, we were issuing a million certificates every day. In 2020 we reached a billion total certificates issued and as of late 2025 we’re frequently issuing ten million certificates per day. We’re now on track to reach a billion active sites, probably sometime in the coming year. (The “certificates issued” and “certificates active” metrics are quite different because our certificates regularly expire and get replaced.) The steady growth of our issuance volume shows the strength of our architecture, the validity of our vision, and the great efforts of our engineering team to scale up our own infrastructure. It also reminds us of the confidence that the Internet community is placing in us, making the use of a Let’s Encrypt certificat...