Convert a certificate between PEM (Base64 text wrapped in BEGIN/END lines) and DER (raw binary) and download the result. The conversion is a Base64 decode or encode, performed in your browser with nothing uploaded. The command-line equivalents are `openssl x509 -in cert.pem -outform der -out cert.der` and `openssl x509 -in cert.der -inform der -out cert.pem`.
The command-line equivalent
openssl x509 -in certificate.pem -outform der -out certificate.der
openssl x509 -inform der -in certificate.der -out certificate.pem
See PEM to DER and DER to PEM for keys, CSRs and bundles as well as certificates.
Frequently asked questions
Does converting change the certificate?
No. PEM is DER Base64-encoded with header and footer lines, so converting re-encodes identical bytes. The signature stays valid and the fingerprint is unchanged.
Why can I not see the DER as text?
Because it is binary. Use the download button to get a real .der file. The Base64 and hex views are provided for pasting into systems that want one of those forms.
Can I convert a private key here?
The conversion works for any DER structure, but do not paste a private key into a converter when openssl pkey -in private.key -outform der -out private.der does it locally in one command.
How do I tell which encoding a file already uses?
Look at the first byte. 0x30 is DER; a - character is the start of a PEM header. The tool detects this automatically and tells you which direction it converted.