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I have a .cer certificate and I would like to convert it in .pem format.

If I remember correctly in the past (6 years ago), I have converted them simply exporting the .cer in Base64, and renaming it in .pem .

How to I convert it from .cer to .pem?

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2 Answers 2

up vote 16 down vote accepted

Convert a DER file (.crt .cer .der) to PEM

openssl x509 -inform der -in certificate.cer -out certificate.pem


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When openssl is not available on your system you could alternatively convert certificates with the java keytool.

However you have to create a java keystore (JKS) first. The certificates can then be imported and exported in different formats.

keytool -genkey -alias test -keystore <key store file>
keytool -delete -alias test -keystore <key store file>

Converting from DER to PEM:

keytool -import -trustcacerts -alias test -file <der certificate file> -keystore test.keystore 
keytool -exportcert -alias test -file <pem certificate file> -rfc -keystore test.keystore

This blog post explains how to convert certificate formats in detail

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