Let's Encrypt SSL 
Let's Encrypt SSL certificate is a free, automated SSL/TLS certificate provided by the Internet Security Research Group, a non-profit organization, which aims to promote global HTTPS promotion, protect user data security, and simplify certificate acquisition and renewal through automated processes.

AboutLet's Encrypt
Let's Encrypt SSL certificates are branded by the Internet Security Research Group (ISRG), a non-profit organization that automates the complex process of manually creating and installing certificates and promotes the ubiquity of encrypted connections to World wide Web servers. The most important feature of Let's Encrypt is the provision of free SSL/TLS certificates, which allows any website to obtain HTTPS encryption for free and increase the security of user data. Let's Encrypt uses an automated certificate issuance process, and certificates can be easily obtained through simple commands or API. The application, verification, and installation of certificates are mostly automated.
Why choose Let's Encrypt
Free of charge
Let's Encrypt provides a free SSL/TLS certificate, which enables any individual or organization with a domain name to implement HTTPS encryption for its website locally, thus increasing the security of user data.
Automation
The certificate issuance process is highly automated, and users can easily obtain certificates through simple commands or API. Most of the certificate application, verification and installation process can be completed automatically, which greatly reduces the complexity of manual operation.
Support HTTPS promotion
Let's Encrypt is committed to promoting HTTPS worldwide by providing free SSL/TLS certificates to encourage more websites to adopt the HTTPS protocol, thus improving network security and the level of user privacy protection.
Short-term validity period
Certificates issued by Let's Encrypt are usually valid for 90 days, which means that users need to update their certificates regularly. Although this increases the complexity of management, it also improves security because the shorter validity period of the certificate reduces the risk of long-term theft of the private key.
Open source and transparency
Let's Encrypt is an open source project, and its code and certification process are open and transparent. This helps to build user trust in the certification process and to promote community contribution and review of the project.
Extensive browser support
Let's Encrypt has been cross-signed by IdenTrust, which means that its certificate has been trusted by mainstream browsers such as Mozilla, Google, Microsoft and Apple. Users do not need to worry about the compatibility of certificates in browsers.