SSL Certificate Checker

Check any domain’s SSL/TLS certificate — issuer, SANs, chain, public key, TLS protocol and expiry — instantly and free.

How it works

1
We open a TLS handshake to the domain on port 443.
2
We read the certificate — subject and SANs, issuer chain, validity window, public key and the negotiated TLS protocol and cipher.
3
We report expiry, trust status and key rotation — the same signals our monitor watches.

Is it free?

Yes — checking a certificate is free and needs no signup.

What are SANs?

Subject Alternative Names are every hostname the certificate is valid for — e.g. example.com and www.example.com on one cert.

Can you alert me before it expires?

Yes. Add the domain in our Telegram bot @gmediatoolsbot and we’ll alert you on changes.

Why does an expired certificate still show details?

We read the certificate even if the chain is expired or untrusted, so you can see exactly what’s wrong.