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PUBLIC WEB DIAGNOSTIC
SSL Certificate Checker
Review a public HTTPS certificate and its expiry date.
Methodology
Resolve the hostname first, reject reserved addresses, then make one verified TLS connection to port 443. Certificate fields come from that public handshake only.
What the result means
Subject, issuer and certificate dates. Treat it as a practical observation rather than a guarantee about every user or provider.
Limitations
Only HTTPS port 443 is checked from one location. Unavailable results are reported honestly instead of guessed.
Worked example
For example.com, inspect the displayed issuer and expiry date. If expiry is within 30 days, schedule renewal before the certificate is replaced.
FAQ
Does it change my certificate?
No. It only reads public certificate information.