Caddy

Caddy is an open-source web server platform that provides automatic HTTPS by default for all hosted sites. It functions as a web server and reverse proxy, designed to handle TLS certificates and secure connections without manual intervention. The software is deployed as a single binary that runs on various operating systems with no external dependencies, meaning it does not require libc to operate. This makes it suitable for a wide range of environments, from simple home servers to large scale production clusters.

Users can manage the server through a command line interface or a JSON API for dynamic configuration changes. While JSON is the native configuration language, Caddy uses config adapters to accept input from other formats, including the Caddyfile, YAML, TOML, and NGINX configurations. This flexibility allows administrators to choose the configuration method that best fits their workflow, whether they prefer static files or programmatic updates via an API.

Key features

• Automatic HTTPS via ZeroSSL and Let's Encrypt
• Support for HTTP/1.1, HTTP/2, and HTTP/3
• Configuration via Caddyfile or native JSON API
• Fully-managed local CA for internal names and IP addresses
• Modular architecture for plugin extensibility
• Encrypted ClientHello (ECH) support
• Multi-issuer fallback for certificate management
• Zero external dependencies including libc

Caddy is architected as a platform to run Go applications, where specific functionalities are implemented as modules. The standard installation includes the tls and http apps, but the plugin system allows for further customization through the xcaddy build tool. Because it is written in Go, the server provides higher memory safety guarantees than many other web server implementations. It is intended for developers and system administrators who require a server capable of managing millions of TLS certificates and serving trillions of requests.

Caddy positions itself as an extensible server platform focused on security and automation.