Reverse proxy

A reverse proxy receives requests from the internet and forwards them to applications running behind it, then returns their responses. To the visitor there is one site; behind it there may be several separate services.

It is the natural home for everything that should be handled the same way for every application: TLS certificates and their renewal, compression, caching, security headers, redirects, and routing by hostname or path.

This is how one modest server can host several unrelated sites cleanly. Each application listens only on the local machine and knows nothing about certificates or domains; the proxy owns the public surface and decides what reaches whom.