SSL certificate checker: validity and chain | TwojeIP.net
Check the SSL/TLS certificate of any site or server: validity, issuer, trust chain, alternative names and TLS version.
What does the SSL check show?
We connect to the server the way a browser does and fetch its certificate. We show the validity date and the days left, the issuer, the key algorithm and length, the SHA-256 fingerprint, the alternative names (SAN) and the whole certificate chain.
We also verify that the server name matches the certificate and that the chain is trusted, and we warn about an expiring, self-signed or weak-key certificate.
What should I do when a certificate is about to expire?
Renew it with your issuer or enable automatic renewal (e.g. Let's Encrypt with certbot). Plan the renewal at least 30 days before expiry.
Why does the browser not trust the certificate?
Most often the server is missing the intermediate certificate, the certificate is self-signed, it has expired or the site name does not match the certificate.
Which ports can I check?
Port 443 (HTTPS) and 465, 993, 995, 636 and 8443. Private addresses are excluded.