What this checker tests
- Certificate availability and dates
- Hostname matching
- Issuer, subject, and alternative names
- TLS protocol and cipher where available
Free domain diagnostic
SSL Certificate Checker
Inspect certificate validity, hostname matching, expiration, issuer, and TLS details.
How to understand the result
A valid certificate must be current, trusted, and issued for the requested hostname.
Certificates close to expiration deserve attention even when they are still valid.
Technical certificate fields are available after the simple diagnosis.
Common problems
- Expired or not-yet-valid certificates
- Hostname mismatch
- Untrusted or incomplete certificate chain
- Connection timeout on port 443