Convert CRT to PEM — Free Online Certificate Converter
Convert a .crt DER binary certificate to PEM Base64 format for Nginx, Apache, and Linux servers — 100% client-side.
Frequently Asked Questions
The .crt Certificate Format Explained
The .crt file extension is one of the most confusing in the SSL/TLS world because it does not indicate a specific encoding — it merely indicates the file contains a certificate. A .crt file may be either PEM (Base64 text) or DER (binary), and you have to inspect the file to know which.
Most certificate authorities deliver certificates as DER-encoded .crt files when serving Windows clients. When you click "Download Certificate" in Internet Explorer or Edge, you often receive a DER .crt file. Apache on Linux has historically preferred PEM .crt files, which is why this inconsistency exists.
This converter automatically detects whether the uploaded .crt file is already in PEM format. If it detects the PEM header, the file is returned unchanged. If the file is DER binary, it is Base64-encoded and PEM headers are added.
After conversion, the resulting .pem file can be used in Nginx (ssl_certificate), Apache (SSLCertificateFile), HAProxy (crt), or any tool that accepts PEM-formatted X.509 certificates.