TLS Certificate Checker

Check a server's TLS certificate chain, expiry, hostname match and supported TLS versions. Works for HTTPS, mail and LDAPS ports.

When a certificate expires, is missing a hostname, or the server forgets to send its intermediate certificate, visitors get a full-page browser warning and mail clients refuse to connect. This connects to the server the way a client does and shows exactly what it presents: the certificate chain, whether it validates and why not, how long until it expires, and which TLS versions it still accepts. Works for web servers, for mail servers (SMTP, IMAP and POP3, including STARTTLS on ports 25, 587, 143 and 110) and for directory (LDAPS) ports.