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SSL Certificate Checker

Beta

Check a website’s SSL certificate and when it expires.

The domain you enter is sent to UtilSlate’s server, which connects to it and reads the certificates it presents. Nothing is stored.

What you get

  • Trusted or not
  • Expiry and chain
  • The connection

Questions

How does it read the certificate?

UtilSlate’s server opens a connection to the site and starts a TLS handshake (TLS 1.3 or 1.2), just far enough to receive the certificates, then closes it. Your browser then checks them: each signature against its issuer’s key, the dates, and that the chain ends at one of the roots Mozilla trusts for websites (the list Firefox uses). Revocation isn’t checked. Paste a certificate into the Certificate Decoder to see every detail.

What does “incomplete chain” mean?

Servers should send their certificate plus the intermediate certificates that link it to a trusted root. Some browsers can fill a gap, others (and many apps) can’t, so a missing intermediate breaks the site for some visitors.

Why can’t it check sites on Cloudflare?

UtilSlate runs on Cloudflare, and Cloudflare doesn’t let its own servers open direct connections to addresses on its network. Sites served through Cloudflare (a large share of the web) can’t be checked here; the page says so. Your browser can show their certificate: click the padlock in the address bar.

Can it check mail servers or other ports?

The ports that speak TLS from the start: 443 and 8443 for websites, 465 for SMTP, 993 for IMAP, 995 for POP3, 636 for LDAPS and a few more. Ports that switch to TLS later with STARTTLS (like 25 or 587) aren’t supported, and other ports are refused so the checker can’t be used to probe other services.

Is it free? Do I need an account?

It is free to use and there is nothing to sign up for. There are no watermarks and no daily limits.

Missing something, or not working as it should? Tell us