SSL Certificate Checker
Enter a domain name (optionally with a port). We connect over TLS and inspect the certificate the server presents.
An SSL/TLS certificate is what enables the padlock in the browser and encrypts traffic between your visitors and your server. This checker opens a live TLS connection to any hostname and reports on the certificate the server actually presents: who issued it, when it expires, which hostnames it covers, the full chain from your leaf certificate up through the intermediate and root CAs, the negotiated protocol and cipher, and the public key strength. It then grades the certificate from A to F and flags anything a browser would reject. Expired, self-signed, mismatched, or chain-incomplete certificates are the most common cause of the "your connection is not private" warning, and they quietly cost you visitors, sales, and SEO ranking.
Enter a domain name and click "Check Certificate." You can add a port for non-standard TLS services, for example mail.example.com:993. The tool connects over TLS, reads the certificate, and shows the grade, full certificate details, Subject Alternative Names, the certificate chain, and the negotiated protocol and cipher. Because it deliberately does not reject broken certificates, it will still show details for expired or self-signed certs so you can diagnose exactly what is wrong. Use the Copy buttons to grab the serial number or fingerprint.
The single most important field is the expiry date. Set a reminder or, better, automate renewal so a certificate never lapses. Let's Encrypt certificates are free and renew automatically. If you see a hostname mismatch, the certificate is valid but was issued for a different name, so reissue it with your hostname in the SAN list. If a browser complains but this tool shows the leaf as fine, the intermediate chain is probably missing: install the full chain (fullchain.pem or the ca-bundle) rather than just the leaf certificate. Always run TLS 1.2 and TLS 1.3 only, and disable SSLv3, TLS 1.0, and TLS 1.1.
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