Caddy Web Server with Automatic HTTPS

Caddy is an open-source web server and reverse proxy written in Go. It is listed here because it removes certificate management as a separate job. By default Caddy obtains and renews TLS certificates for every site it serves, with no extra tools or cron jobs, and it redirects HTTP to HTTPS on its own.

Its On-Demand TLS feature is popular with SaaS platforms that let customers use their own domains. Caddy fetches a certificate during the first TLS handshake for a new domain, then keeps it renewed. The project says this is designed to scale to hundreds of thousands of sites, and several Caddy instances that share storage will coordinate certificate management as a fleet.

Caddy can also serve HTTPS for localhost and internal names using its own local certificate authority, which is handy for development. Its TLS defaults are chosen so that most sites need no manual tuning.

Configuration comes in two forms. The Caddyfile is a short, readable format for common setups such as static files or a reverse proxy in front of an app. The native JSON config can be read and changed live through a REST API, which suits automation. Plugins add features such as DNS providers for wildcard certificates, and the site keeps an official list of registered modules. The documentation includes tutorials on static file serving, reverse proxying and troubleshooting, plus articles on logging, monitoring, profiling and running Caddy as a system service, and a guide to writing your own module.

Caddy is free under the Apache 2.0 licence. Development is funded by sponsorships, which also give businesses tangible benefits such as support. Documentation, tutorials and a community forum are on the project site.