Let's Encrypt is a trustworthy, free, automated, and open Certificate Authority (CA) which provides TLS/SSL certificates to enable HTTPS encryption on websites.
An SSL/TLS certificate (What are SSL/TLS Certificates?) is a type of digital certificate used to secure the communication between a browser or other applications and a website or web service.
Let's Encrypt is a very popular and trustworthy CA run by the non-profit Internet Security Research Group (ISRG). It is aiming to make the web more secure and privacy-respecting. The process is fully automated, removing complex manual creation and renewal steps.
Anyone with a domain name can obtain a trusted certificate from Let's Encrypt and their certificates are trusted by all major browsers. They offer Domain Validation certificates, which verify that the applicant controls a specific domain.
Before Let's Encrypt, which was launched in 2015/2016, obtaining SSL/TLS certificates was a manual, often costly process involving commercial Certificate Authorities (CAs) like Verisign or Thawte. Users paid per-hostname, validated domains manually, and managed renewals annually, which created high barriers and led to low HTTPS adoption. Let's Encrypt revolutionized this by introducing free, automated, and open certificate issuance, making HTTPS the default standard for the web.
