SSL certificate checker
Enter a hostname and get its live certificate details: expiry with days remaining, issuer, negotiated protocol and cipher, and the names the certificate covers. The TLS probe runs on our infrastructure (a browser cannot inspect another site's certificate), powered by the Alertkick tools API.
When to worry
Public certificates now live at most 398 days and the ecosystem is moving shorter, so renewal should be automated (ACME / Let's Encrypt) rather than remembered. Under 30 days with no automation in sight is a ticket; an expired certificate is every browser turning users away at the door. While you are here, the domain itself expires too: domain expiry checker.
Certificates and domains are half the story.
For always-on monitoring of certificates, domains and uptime, our sister product Alertkick does exactly that. Moorfox watches the machines; Alertkick watches the websites.