How to use Caddy for certificates only, without binding to ports?

[francislavoie]

There’s no way to do that with a Caddyfile. Use a JSON config for that.

Using Caddy to keep certificates renewed

You can use Caddy as an automated certificate manager to keep certificates renewed without having to run an HTTPS server [1]. This way, the certificates can be used by other programs that need them. Caddy’s tls app can be configured without the need for an HTTP server. It can keep certificates renewed. Without additional configuration, assets (certificates, keys, and metadata) are stored in a data directory on the local file system at a location dependent upon your OS. The simplest form is to …

You can adapt your config to JSON, and then just delete the whole http app. Only the tls app is needed.