Caddy

Caddy is an open-source web server written in Go that serves sites over HTTPS by default, automatically obtaining and renewing TLS certificates for all configured domains. It also provides a reverse proxy, a production-ready static file server, and an online configuration API, reducing the need for external certificate tooling and separate infrastructure components.

Key capabilities include On-Demand TLS for dynamically provisioning certificates during handshakes, internal PKI and private certificate authorities, cluster coordination across instances sharing storage, and a RESTful config API for runtime configuration. The reverse proxy supports load balancing, health checks, dynamic upstreams, retries, and protocols including HTTP, HTTPS, WebSockets, gRPC, and FastCGI. The static file server handles compression, virtual file systems, range requests, and ETags. Configuration can be written in JSON, Caddyfile, YAML, TOML, HCL, and other formats via adapters, with graceful zero-downtime reloads. Caddy runs on major operating systems and CPU architectures, compiles to static binaries, and can be extended with compile-time plugins.

Caddy is suited to developers and infrastructure teams managing web serving, TLS automation, reverse proxying, and internal certificate authorities. It is free software supported by sponsorships, which can include private support and training.