What does this SSL checker do?

This tool connects to your domain over HTTPS and reads the SSL/TLS certificate presented by the server — exactly like a browser does. It shows you the expiration date, how many days remain until the certificate becomes invalid, and which certificate authority issued it. No data is stored and no signup is required.

Why it matters: an expired certificate takes your site offline for most visitors instantly. Browsers block the page with a security warning, mobile apps and API clients fail with TLS handshake errors, and recovering trust takes far longer than renewing a certificate. Most outages caused by expired certificates happen not because nobody cared, but because automated renewal silently broke — which is why checking (and monitoring) expiry dates is a standard part of every production checklist.