What This Tool Checks
HeaderCheckr follows safe redirects, inspects the final HTTPS certificate, and reports the issuer, subject, validity, and expiry.
Security
SSL Certificate Checker
Check the issuer, expiration date, and validity of a website certificate.
Guide
SSL Certificate Checks
TLS certificates are what let browsers trust an HTTPS connection to the site they meant to visit.
This checker helps you catch common certificate problems before visitors see browser warnings or monitoring alerts.
Why It Matters
Expired certificates, missing intermediate certificates, or hostname mismatches can make browsers block a site before any page content loads.
A quick certificate check is especially useful after DNS, CDN, load balancer, or hosting changes.
Related Tools
Once HTTPS is healthy, check the Security Headers Checker and HTTP Protocol Checker for the same site.
FAQ
What makes an SSL certificate invalid?
Common causes include expiry, hostname mismatch, an incomplete certificate chain, or an issuer that browsers do not trust.
Should I check the origin or CDN certificate?
Check the public URL your visitors use first. If a CDN sits in front of the origin, browsers usually see the CDN certificate.
How soon should I renew a certificate?
Automatic renewal is best. If a certificate has less than two weeks remaining, treat it as something to fix soon.