Let's Encrypt, a nonprofit certificate authority, has issued billions of free SSL/TLS certificates since its launch in 2015, making it the largest certificate authority in the world. The organization has played a significant role in increasing the prevalence of HTTPS encryption on the web, with the global percentage of encrypted connections rising from below 30% to around 80% over the past decade. Let's Encrypt's automated certificate issuance process has made it easy for website owners to obtain and renew certificates, contributing to the widespread adoption of HTTPS. The organization is celebrating its 10-year anniversary and reflecting on its achievements and future goals.