Enabling HTTPS in Dream is very easy: just pass ~tls:true to Dream.run:

let () =
  Dream.run ~tls:true
  @@ Dream.logger
  @@ fun _ -> Dream.html "Good morning, world!"

$ cd example/l-https
$ opam install --deps-only --yes .
$ dune exec --root . ./https.exe

However, when you visit https://localhost:8080, you will have to click through a bunch of certificate errors. That's because, by default, Dream uses a compiled-in localhost certificate, which is suitable only for development. The certificate is technically valid, but it is self-signed, and the browser rightly recognizes it as dubious.

For production, be sure to obtain a real certificate, for example, from Let's Encrypt. Pass the certificate to Dream.run with ~certificate_file and ~key_file. Dream will remind you to do this in the logs if you try to use the built-in self-signed certificate when not running on localhost.

Enabling HTTPS also enables upgrading of connections to HTTP/2, if the client requests it. Whether HTTP/1.1 or HTTP/2 was used is completely transparent to the Web app, though it can examine the protocol version by calling Dream.version on any given request.

That's all for the tutorial!

Up to the tutorial index