SSL Certificate Checker
Inspect TLS certificate validity, expiry, issuer, SANs and chain depth for any host.
About SSL Certificate
Checks a domain's TLS certificate — validity dates, issuer, subject, and the full certificate chain up to the root — in one query, without needing to open a browser and dig through its certificate viewer. Certificate expiry is one of the most common self-inflicted outages in production. Chain issues are often the actual cause of an "invalid certificate" error even when the end-entity certificate itself looks fine — a missing intermediate certificate will pass in browsers that cache it while failing in ones that don't.
A wildcard certificate like *.example.com covers exactly one subdomain level — it doesn't cover a second-level subdomain like sub.another.example.com, a common assumption that leads to an unexpected certificate mismatch.