Check a certificate

Enter a hostname to inspect the TLS certificate chain the server actually presents.

Checks port 443 only. Hostnames only — IP addresses are not supported.

Known limitation: A Cloudflare Worker cannot open a TCP connection to another host behind Cloudflare. Targets on Cloudflare will be reported as unreachable — this is a platform limitation, not a problem with the target server.

Checking certificate chain…
Subject Issuer Expires Days remaining Fingerprint Covered hostnames
Certificate chain