What This Tool Shows
- Certificate information (issuer, validity dates, domains)
- Certificate chain verification to root CA
- TLS protocol version and cipher suite used
- HSTS header check for downgrade attack protection
- Security grade from A+ to F with explanation
SSL Certificate Types
- DV (Domain Validation)
- Basic certificate. Only verifies domain ownership. Issued automatically in minutes. Free options include Let's Encrypt.
- OV (Organization Validation)
- Corporate certificate. Verifies organization existence. Requires document verification. Displays company name.
- EV (Extended Validation)
- Extended validation certificate. Strict legal entity verification. Previously showed green bar with organization name in browsers.
Security Grade Explanation
- A+ — Excellent
- Modern TLS 1.3, HSTS header, complete certificate chain, more than 30 days until expiry.
- A — Good
- TLS 1.2 or 1.3, strong ciphers, valid chain. HSTS may be missing.
- B — Satisfactory
- Basic protection works, but there are configuration issues. Improvement recommended.
- C — Poor
- Serious security issues. Outdated protocols or weak ciphers.
- D/F — Critical
- Critical vulnerabilities. Expired certificate, incomplete chain, or outdated TLS 1.0/1.1.
Common SSL Errors
- ERR_CERT_DATE_INVALID
- Certificate has expired or is not yet valid. Check server date and renew the certificate.
- ERR_CERT_COMMON_NAME_INVALID
- Domain doesn't match the certificate name. Check SAN (Subject Alternative Names) and issue a new certificate.
- ERR_CERT_AUTHORITY_INVALID
- Certificate is not signed by a trusted certificate authority. Possibly self-signed or incomplete chain.
- ERR_SSL_VERSION_OR_CIPHER_MISMATCH
- Browser and server cannot negotiate TLS version or cipher. Update server configuration.
When to Check SSL
- Verify SSL configuration before launching a website
- Diagnose HTTPS errors in browsers
- Monitor certificate expiration dates
- Security audit of web applications
- Verify correct certificate installation after renewal