SSL / TLS Checker
Inspect a site’s certificate
Fetch and read a host’s TLS certificate: issuer, validity dates, days until expiry, the TLS version negotiated, and the domains it covers.
How to read the results
- 1.Enter a domain served over HTTPS.
- 2.We perform a TLS handshake and read the certificate — issuer, subject, valid-from / valid-until, days remaining and the covered hostnames (SANs).
- 3.A negative "days left" means the certificate has expired.
Why it matters
An expired or mismatched certificate breaks HTTPS and scares away visitors. Checking the expiry date ahead of time prevents an ugly, avoidable outage.
Frequently asked questions
How early should I renew?
Automate renewal to run well before expiry (30 days is a common buffer). This tool’s "days left" makes it easy to spot certificates that are cutting it close.
What are SANs?
Subject Alternative Names — the full list of hostnames a certificate is valid for, including wildcards.