Check any domain's SSL certificate.
Expiry, issuer, SANs and chain validity.

An SSL certificate check confirms whether a website's HTTPS connection is set up correctly — and, just as importantly, when that setup is about to break. Certificates expire on a fixed schedule, and a lapsed one throws browser warnings that scare visitors off and can hurt search rankings. This tool connects to any domain on port 443, reads its live certificate, and shows you the issuer, the expiry date, every hostname it covers, and whether the chain validates to a trusted root. It's built for agencies and IT teams managing certificates across dozens of client sites, developers tracking down a handshake failure, or anyone who just wants to know how long they've got before a renewal is due. No login, no rate limits.