Online SSL Certificate Checker
Inspect public SSL/TLS certificates, issuer trust chains, and expiration telemetry.
Understanding Your SSL Certificate Health
An SSL/TLS certificate is a cryptographically signed document that binds a cryptographic key pair to a domain name. It enables HTTPS encryption and ensures visitors connect to the authentic server.
1. Subject Alternative Names (SANs)
Modern browsers ignore the legacy Common Name (CN) and rely strictly on SAN entries to verify whether example.com and www.example.com or wildcards (*.example.com) are covered.
2. Certificate Authority (CA)
The issuing authority (e.g. Let's Encrypt, DigiCert, Google Trust Services, Cloudflare) signs the certificate with their trusted root or intermediate key.
3. SHA-256 Fingerprint
A unique cryptographic hash of the entire DER certificate. Comparing fingerprints lets you immediately verify if a renewed certificate is live.