SSL Converter — Free Online Certificate Format Converter
Convert SSL/TLS certificates between PEM, DER, CER, CRT, and PFX/PKCS#12 formats. All conversions run 100% in your browser.
Extract cert + key from a Windows PFX archive
Bundle PEM cert + key into a PKCS#12 archive
Convert binary CER/DER certificate to PEM text
Convert raw DER binary to Base64 PEM
Convert DER-encoded .crt to PEM format
Save PEM as a .crt file for Apache/cPanel
Frequently Asked Questions
SSL Certificate Format Guide
SSL/TLS certificates are stored in several binary and text encoding formats. Each format exists for a historical or platform-specific reason, and different web servers, operating systems, and cloud platforms prefer different formats.
PEM is the Unix/Linux standard. It is a Base64-encoded text file with ASCII armor headers. PEM files can contain a single block (one certificate) or multiple blocks (a full chain). Nginx, Apache, HAProxy, and most cloud load balancers use PEM.
DER / CER is the Windows standard for individual certificates. DER is the raw binary ASN.1 encoding — the same data as PEM but without Base64. IIS sometimes exports certificates as DER .cer files. Java applications and Android also commonly use DER.
PFX / PKCS#12 is a container format that bundles the certificate, private key, and optionally the CA chain into one password-encrypted binary file. Windows IIS, Azure, Exchange, and most Microsoft products use PFX.
CRT is a naming convention, not a format. A .crt file may be either PEM or DER encoded. Apache on Linux traditionally uses .crt for the certificate file, while the private key uses .key.