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dnsdon

SSL Certificate Checker

Check whether a site serves HTTPS, when its certificate expires, whether browsers will trust it, and how HTTP traffic is redirected.

Enter a domain or hostname. Pasted URLs and internationalized names work too.

For TLS services on other ports, such as 8443, 465 (SMTP), 993 (IMAP) or 853 (DNS over TLS). Redirect and HSTS checks run on port 443 only.

What this checks

  • Whether HTTPS is enabled on port 443, or TLS on a port you choose
  • Certificate expiry date and days remaining
  • Hostname coverage and chain trust, with the reason when it fails
  • Whether CAA records still let your certificate authority renew
  • TLS versions, including legacy TLS 1.0 and 1.1
  • IPv4 and IPv6 reachability, and the same certificate on every address
  • HTTP → HTTPS redirect, HSTS and security headers

How to read the results

Pass
The check succeeded based on the observed responses.
Warning
Works now, but is risky, unusual or worth reviewing.
Fail
A problem was observed directly in the responses.
Inconclusive
Not enough evidence — for example a server did not respond.