SSL Certificate Checker
Inspect any domain's TLS certificate, expiry date, issuer, covered domains, and signature details. No login, runs instantly.
Enter a domain without https://. We handle the TLS connection.
Run an SSL check
Certificate issuer, expiry, SAN coverage, and warnings appear here.
SSL Certificate Checker connects to a domain over HTTPS and inspects the certificate it presents: issuer, expiry date, the exact hostnames it covers, and the signature algorithm used to sign it. This occurs before any page content is exchanged and evaluates only whether the encrypted connection itself is trustworthy.
The expiry date is the most consequential field in practice: an expired certificate triggers a full-page browser warning for every visitor, regardless of whether the underlying site is otherwise functioning correctly. Checking a domain's covered hostnames (the Subject Alternative Names) also identifies a common misconfiguration in which a certificate is valid for example.com but not www.example.com, or the reverse.
Certificate problems and DNS problems can produce similar symptoms, such as a site that fails to load. Checking the certificate directly rules out one of the two causes immediately.