Back up with Time Machine
Automatically back up all your files with Time Machine, which is built in to your Mac, or choose another backup method.Create a backup
Prepare your Mac for service
Making a backup is an important part of preparing your Mac for service, especially because some types of repair might require erasing or replacing your hard drive.
How much space do I need for a backup?
To see the size of a specific file or folder, click it once and then press Command-I. To see storage information about your Mac, click the Apple menu in the top-left of your screen. Choose About This Mac and click the Storage tab. For Time Machine backups, it's good to use a drive that has at least twice the storage capacity of your Mac.
Free up storage on your Mac
macOS can save space by storing your content in the cloud. This isn't a backup, but it includes new tools to make it easier to find and remove large or unwanted files before you make a backup.Use Optimized Storage in macOS