SSL certificate checker

See a site's certificate the way browsers do: who issued it, when it expires, which names it covers and whether it's trusted.

Good to know

What happens when a certificate expires?: Browsers show a full-page security warning and most visitors leave. APIs and apps that call the site start failing outright. Certificates from Let's Encrypt last 90 days, so a broken auto-renewal shows up fast.
What does “not trusted” mean?: The certificate is expired, issued for a different name, self-signed, or missing an intermediate certificate in the chain. The message shown explains which.
Get warned before it expires: Spot Downtime's website monitors watch the certificate on every check and warn you 14 days before it expires.

Checking by hand only tells you about right now. Spot Downtime checks your sites around the clock and alerts you by email, Slack or Discord.