A minimal config like that will default to provisioning (and periodically renewing) an SSL certificate from Let's Encrypt automatically, and if there are any issues doing so it will try another free CA.

This requires port 80 and/or 443 to be reachable from the general Internet of course, as that's where those CAs are.

There's an optional extra step of putting

{
    email [email protected]
}

(with your actual e-mail address substituted) at the top of the config file, so that the Let's Encrypt knows who you are and can notify you if there are any problems with your certificates. For example, if any of your certificates are about to expire without being renewed^1^, or if they have to revoke certificates due to a bug on their side^2^ .

As long as you don't need wildcard certificates^3^, it's really that easy.

^1^: I've only had this happen twice: once when I had removed a subdomain from the config (so Caddy did not need to renew), and once when Caddy had "renewed" using the other CA due to network issues while contacting Let's Encrypt.

^2^: Caddy has code to automatically detect revoked certificates and renew or replace them before it becomes an issue, so you can likely ignore this kind of e-mail.

^3^: Wildcard certificates are supported, but require an extra line of configuration and adding in a module to support your DNS provider.