diff --git a/docs/usage/https.md b/docs/usage/https.md
index 0f89705..6e29e76 100644
--- a/docs/usage/https.md
+++ b/docs/usage/https.md
@@ -41,3 +41,8 @@ server {
   }
 }
 ```
+
+You can obtain valid certificates using certbot. If your server is not public,
+then avoid serving it on a subdomain called timelimit. Most CAs provide a public
+log of all issues certificates and using this, it is easy to find your timelimit-server
+installation if the certificate is for ``timelimit.[yourdomain].[tld]``.