PEM is a container format that could, among other things, be used to store SSH public and private key pairs.

PuTTY only accepts .ppk (PuTTY Private Key) files, so you will not be able to use a .pem SSH private key in PuTTY directly. However, you can convert your .pem file to .ppk to use your existing SSH private key in PuTTY.

PuTTY Key Generator or PuTTYGen is a free Windows utility that you can use to convert pem files to ppk.

Steps to convert pem to ppk using PuTTYGen:

  1. Download PuTTY Key Generator (puttygen.exe) from the official website and launch the program.

    https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html

  2. Click on the Load button from PuTTYgen's main interface.
  3. Set the Files of type to All Files (*.*), select your PEM file and click Open.
  4. Enter the passphrase of your PEM private key file if prompted and click OK.

  5. Click OK on the successful import of the file notification.
  6. Edit any key parameters if necessary and click Save private key.
  7. Click Yes if you don't set any passphrase on your key before and getting warned about it.
  8. Select the location and filename to save the generated key and click Save.