SSL & domain expiry
Type a domain and see when its SSL certificate expires, who issued it and for which names, when the domain registration itself runs out and with which registrar, and whether plain HTTP redirects to HTTPS with HSTS.
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How it works
- We open a TLS connection to the domain and read the certificate: issuer, names it covers, valid-from and valid-to.
- The domain registration is looked up through RDAP, the successor of WHOIS, for the expiry date, registrar and status.
- Plain http:// is requested to see whether it redirects to https:// and whether HSTS is sent.
- Anything within 30 days of expiring is a warning; within 7 days or already expired is a fail.
Questions people ask
What happens when the certificate expires?
Every browser shows a full-page warning and most visitors leave. Let's Encrypt certificates last 90 days and renew automatically — until the automation silently breaks. Checking the date is the only way to know.
What happens when the domain expires?
The site, the e-mail and every link to you stop working; after a grace period someone else can register the name. Registrars send reminders to the address on file, which is often an old one.
What is RDAP?
The structured replacement for WHOIS. Not every registry publishes the same fields; some hide the expiry date or the registrar for privacy, in which case the tool says so instead of guessing.
The certificate is fine but the tool says the names do not match. Why?
A certificate covers specific names. One issued for www.example.com does not cover example.com unless both are listed (or a wildcard is). Visitors on the uncovered name get a warning.
What is HSTS?
A header telling browsers to use HTTPS for this domain from now on, even when someone types http://. It closes the one-request window where a connection is still unencrypted.
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