Security guides

Many security errors come from configuration rather than attacks. A certificate can be valid and still be rejected because the server sends an incomplete chain, or because the certificate does not cover the hostname being requested.

These guides explain how TLS trust works in practice: how root, intermediate and leaf certificates link together, how clients validate them, and why the same site can load in a browser but fail from curl, a mobile app or an API client.

To inspect a live host, use the SSL Certificate Checker. The Hash Generator is useful when you need to compare fingerprints or checksums.