Security Certificates: PEM, DER & PKCS#12
Base64 ASCII armoring, binary DER certificates, and private key containers.
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Format Comparison & Technical Specifications
| Output Format | MIME Type | Specification | Type |
|---|---|---|---|
| PEM Certificate | application/x-pem-file | RFC-7468-PEM | Base64 Armored Certificate |
| CRT Certificate | application/x-x509-ca-cert | RFC-5280-X509 | X.509 Public Certificate |
| CER Certificate | application/pkix-cert | RFC-5280-X509 | X.509 Security Certificate |
| DER Binary | application/x-x509-ca-cert | RFC-5280-X509 | ASN.1 Binary Certificate |
| P12 PKCS #12 Bundle | application/x-pkcs12 | RFC-7292-PKCS12 | Encrypted Certificate Archive |
| PFX Package | application/x-pkcs12 | RFC-7292-PKCS12 | Microsoft Personal Exchange |
Technical Specifications & Codec Breakdown
PEM vs. DER: Text vs. Binary
DER is the binary ASN.1 encoding of an SSL/TLS certificate. PEM is simply that exact binary data converted to Base64 text with '-----BEGIN CERTIFICATE-----' headers, allowing certificates to be copy-pasted into web servers and text configs.
PKCS#12 (.pfx / .p12): Bundling Key & Certificate
A PEM certificate contains only the public certificate. When migrating certificates between Windows servers or Java keystores, PKCS#12 packages the public certificate, the full certificate trust chain, and the encrypted private key into a single password-protected file.
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