A KRNL key is a code that you need to use the KRNL executor. When you open KRNL, it often asks for this key to make sure you’re a legitimate user. You can usually get the key from the KRNL website or through a prompt in the application. After entering the key, you can start using KRNL to run scripts in Roblox games. Keep in mind that sharing or using keys from untrusted sources can lead to issues, so it’s best to stick to the official channels!