ServerMonitor

SSL certificate checker

See in seconds whether a website's HTTPS certificate is valid, who issued it and when it expires.

Enter a domain name or a web address. We only look at what any visitor can see.

What this check does

  • We connect to the website on port 443 like a browser would.
  • We read the certificate: issuer, validity dates, covered names and TLS version.
  • We verify the certificate chain and that the certificate matches the hostname.

Frequently asked questions

Why do certificates expire?
Certificates are valid for a limited time (often 90 days to a year) to limit the damage of a stolen key. They must be renewed before they expire, otherwise browsers show a security warning.
What does "hostname does not match" mean?
The certificate was issued for other names than the one you entered. Visitors will see a warning in their browser.
Can I get a warning before my certificate expires?
Yes. Create a free account and we will alert you well before the expiry date.