SSL Checker
Verify SSL certificates, issuer, expiry date and TLS version.
Issuer & chain
See which authority issued the cert and if the chain is complete.
Expiry countdown
Days remaining before renewal is needed.
TLS version
Confirms which protocol version is negotiated.
Domain coverage
Checks the cert actually covers the domain you're serving.
How it works
This tool connects to a domain's HTTPS port and reads back its certificate: the issuing authority, validity dates, the domains it covers, and which TLS protocol version is in use.
An expired certificate is one of the most common (and most avoidable) causes of a site suddenly showing browser security warnings — checking expiry ahead of time takes a few seconds and prevents an outage that otherwise arrives with no warning.
Related reading
Frequently asked questions
What does it mean when a certificate is valid but the browser still shows a warning?
This usually means the certificate is valid for a different hostname than the one being visited — for example, a certificate covering example.com but not www.example.com. The certificate itself can be perfectly valid and still trigger a warning for the wrong domain.
How far in advance should I renew my SSL certificate?
Most automated renewal systems (like Let's Encrypt) renew about 30 days before expiry — if you're managing renewal manually, checking with at least two weeks of buffer avoids a last-minute scramble.
Does this tool check the full certificate chain?
It reports the certificate actually presented by the server, including chain information where the server provides it — an incomplete chain (missing an intermediate certificate) is a common misconfiguration that shows correctly in some browsers but fails in others.
Is a self-signed certificate the same as an invalid one?
Not exactly — a self-signed certificate is technically valid cryptographically but isn't issued by a trusted certificate authority, so browsers flag it as untrusted rather than expired or misconfigured. It's fine for internal testing but shouldn't be used on a public-facing site.
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