I have exported my certificates in DER encodig (with the extension .cer). Is there a way to convert those certificates in Base-64 encoding (with the same extension)? Thanks

  • 1
    The extension (as all the filename) is irrelevant. It only exists to make human life easier, computers do not care, only the content of the file matters for them. "Base-64 encoding" is called PEM in the "SSL" world. Nov 25, 2019 at 17:39

2 Answers 2


To convert from a DER to a base64, you can use certutil :

certutil -encode filename.cer newfilename.cer

And from a base64 to a DER, you can use :

certutil -decode filename.cer newfilename.cer
  • Tanks for the help ;)
    – Warok
    Nov 21, 2019 at 11:26
  • 1
    certutil is not part of the OpenSSL suite of tools as far as I know. Nov 21, 2019 at 14:52

As you have the openssl tag on your question, you should use:

openssl x509 -inform der -in infile.cer -out outfile.cer

In the reverse direction:

openssl x509 -outform der -in infile.cer -out outfile.cer

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