If you are going to use an external hard drive or an external solid-state drive to back up your Mac data, then you should start by formatting it for the MacOS extended file system - besides a few exceptions, most external hard drives are not pre-formatted for Macs. Make sure your drive is properly formatted These methods also work for MacOS Big Sur. If you’re looking to ensure you don’t experience the severe pain that is data loss, we’ve broken down the best way to back up your Mac and protect your information. It’s always a good idea to have multiple forms of backup (local backup and remote backup) when possible. With online storage services like iCloud or even Google Drive, some people assume that there’s no need for an external hard drive on your Mac.