An expired or mismatched certificate triggers browser warnings and erodes trust. This tool connects to the host and shows the validity, the expiry date, the issuer and whether the certificate matches the hostname.
What this tool does
The tool sets up a TLS connection to the host, reads the presented certificate and checks the validity period, the issuer, the TLS version and the hostname match including alternative names.
How to use it
Enter the hostname and run the check. That way you see at a glance whether a site is securely reachable and when you need to renew.
Input and output
- Input: a hostname
- Output: the validity, the expiry date, the issuer, the TLS version and the hostname match
Limitations
The tool checks the certificate on port 443; certificates on other ports or behind client certificate authentication are not read.
Good to know
Set a reminder well before the expiry date, or use automatic renewal such as with Let's Encrypt, so a certificate never expires unnoticed. On a mismatch, check that all hostnames in use are actually listed in the certificate.