SSL Certificate Decoder
Paste any PEM SSL/TLS certificate and instantly inspect its subject, issuer, expiry date, SANs and more. Runs entirely in your browser.
🔒 Security Tools
Free
Browser-based
What is a PEM Certificate?
PEM (Privacy-Enhanced Mail) is the most common format for SSL/TLS certificates. It is a Base64-encoded DER certificate wrapped in -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- headers. Certificates in this format are used by web servers, email servers and other TLS-enabled applications.
Key Certificate Fields
| Field | Description |
|---|---|
| Common Name (CN) | The domain or entity the certificate is issued to |
| Subject Alternative Names | Additional domains covered by the certificate (wildcard etc.) |
| Issuer | The Certificate Authority (CA) that signed the certificate |
| Not Before / Not After | Validity period — certificate is rejected outside this range |
| Serial Number | Unique identifier assigned by the CA |
| Signature Algorithm | Algorithm used to sign the certificate (e.g. SHA256withRSA) |
Where to Get a Certificate
You can obtain a server's PEM certificate using: openssl s_client -connect domain.com:443 </dev/null 2>/dev/null | openssl x509