SSL Certificate Checker
Check any website's SSL/TLS certificate instantly. See when it expires, how many days are left, and who issued it — before your visitors see a security warning.
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.
Frequently Asked Questions
What happens when an SSL certificate expires?
Browsers immediately show a full-page security warning ("Your connection is not private") and most visitors leave. APIs and integrations that call your endpoints fail with TLS errors. Search engines may also lower rankings for sites with invalid certificates.
How long are SSL certificates valid?
Most certificates issued today are valid for a maximum of 398 days (about 13 months). Free certificates from Let's Encrypt are valid for 90 days and are designed to be renewed automatically. Because renewal automation can silently break, regular expiry checks are essential.
How can I get alerted before my certificate expires?
Set up automated monitoring. UptimeEye checks your certificates continuously and emails you 30, 14 and 7 days before expiration — plus alerts via Slack, Discord, PagerDuty and more. The free plan covers this out of the box.