warnwell

Warnwell / Checks

SSL certificate checker: expiry and errors

Paste your domains or subdomains. Warnwell opens each site over HTTPS like a browser would, reads the certificate dates from the public Certificate Transparency logs, and says which ones run out soon.

  • Free
  • No sign-up
  • Up to 50 domains at once

01

What it checks

  • Does HTTPS open? If the site shows an expired certificate, one made for another name, or none at all, you get "Certificate for shop.example.com expired or not made for it" or "shows the wrong certificate".
  • End date. From the CT logs, the newest certificate issued for that exact host, with its issuer and the days left.
  • About to run out. Amber when fewer than 14 days are left (or a fifth of the certificate's life, for short ones) and no newer certificate has been issued. Most hosts renew automatically around 30 days before the end, so a certificate that gets that close usually means renewal failed.
  • The rest of the site. http to https redirects, www, redirect chains, HSTS and parking pages, in the same row.

Subdomains work: paste shop.example.com and its own certificate is checked.

02

What it does not check

Warnwell does not grade TLS versions or cipher suites, and it does not catch revoked certificates. For a deep test of one server, SSL Labs is the standard. Warnwell is for the question "which of my 40 sites has a certificate problem this month".

Certificate Transparency shows what was issued, not what is installed. If a host was issued a new certificate but still serves the old one, the HTTPS check catches it, because the site then fails to open.

03

Questions

How do I check when an SSL certificate expires?
Paste the domain above. In a browser you can also click the padlock, then the certificate, and read "Expires on". That works one site at a time.
Why does it show a different issuer than my browser?
Some hosts, Cloudflare for one, keep two certificates from different authorities for the same name. When that happens Warnwell leaves the issuer out.
Does it check certificates on mail servers?
No, only the website on the domain and the www name.
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Updated 20 Oct 2026.