Certificates are used to secure communication between clients and servers over the internet. Different types of certificates exist, including the CER and PEM formats. In this article, we’ll discuss how to convert a CER certificate to a PEM format using the Certutil tool.

What is Certutil?

Certutil is a command-line tool in Windows that is used to manage certificates. It can be used to display and verify the certificates, as well as to convert them from one format to another.

Converting CER to PEM

To convert a CER certificate to a PEM format using Certutil, follow the steps below:

  1. Open a command prompt and navigate to the directory where the CER certificate is saved.
  2. Type the following command: certutil -encode inputfile outputfile
  3. Replace inputfile with the name of the CER certificate file you want to convert.
  4. Replace outputfile with the name you want to give to the PEM certificate file.
  5. Press Enter to execute the command.


Suppose we have a CER certificate file named mycert.cer saved in the C:\certs directory. We want to convert it to a PEM certificate file named mycert.pem and save it in the same directory. We can use the following command:

certutil -encode C:\certs\mycert.cer C:\certs\mycert.pem

Benefits of Using Certutil

There are several benefits to using Certutil to convert certificates:

  • Certutil is a command-line tool, so it’s easy to automate the conversion process.
  • Certutil is included with Windows, so there’s no need to install any additional software.
  • Certutil can handle a wide range of certificate formats, so it’s a versatile tool.

Other Certificate Formats

In addition to CER and PEM, there are several other certificate formats, including:

  • JKS (Java Keystore)
  • PFX (Personal Information Exchange)
  • DER (Distinguished Encoding Rules)
  • P12 (PKCS#12)
  • CRT (Certificate)
  • P7B (PKCS#7)

Certutil can also be used to convert certificates between these formats. The syntax for the command is slightly different for each format, but the general process is the same.


If you encounter any issues while converting certificates using Certutil, there are a few things you can try:

  • Make sure you’re running the command as an administrator.
  • Double-check the syntax of the command to ensure that there are no typos.
  • Verify that the input and output file paths are correct.

FAQs for Convert cer to pem certutil

Certutil is a built-in command-line tool in Windows operating systems used to manage certificate services and public key infrastructure (PKI). It is used to manage certificates, including installing, importing, exporting, backing up, and restoring certificates. It can also be used to manage certificate revocation lists (CRLs), keys, and various other certificate-related tasks.

What is a .cer file?

A .cer file is a digital certificate file that contains information about the identity of its owner and the public key of the owner’s digital signature. It is issued by a Certificate Authority (CA) and is used to verify the authenticity of websites, software, and other digital assets. CER files can be used to install certificates.

What is a .pem file?

A .pem file is a certificate file used mainly in Unix-based operating systems. It contains a public key certificate and its private key. PEM files are frequently used for SSL and TLS communication, and they can also contain other types of certificates or public keys, such as those used for SSH connectivity.

How do I convert CER to PEM certutil?

To convert a CER file to a PEM file using CertUtil, you can use the following command: ‘certutil -encode input.cer output.pem’ where ‘input.cer’ is the source file and ‘output.pem’ is the destination file. This command encodes the binary data of the CER file into PEM format and saves it as a .pem file.

Can I convert multiple CER files to PEM format using CertUtil?

Yes, you can convert multiple CER files to PEM format using CertUtil. In this case, you can use the ‘for loop’ command in Windows shell to iterate through a directory containing CER files and convert them to PEM format using the ‘certutil’ command with the ‘-encode’ option as described above.

How do I verify that the conversion was successful?

To verify that the conversion from CER to PEM format was successful using CertUtil, you can open the resulting PEM file using a text editor such as Notepad. The PEM file should contain the same information as the original CER file, but in a different format. You can also use the OpenSSL command to verify the PEM file’s contents, which considers a more convenient option if you install OpenSSL on your system.