ZeroSSL is a free SSL certificate service similar to Let's Encrypt. ZeroSSL provides a user interface (GUI), ACME integration, and a REST API. Both 90-day and 1-year certificates are supported.
ZeroSSL is a one-stop solution for SSL certificate creation and management, allowing users to create website security certificates issued by ZeroSSL either using a fast and straightforward user interface, using ACME integrations, or using a full-fledged SSL REST API. ZeroSSL supports single-domain, multi-domain and wildcard certificates with the option of choosing between 90-day as well as 1-year certificate validity.