Make automatic backups
Your Mac comes with software to make backing up simple. Just turn on Time Machine and connect an external drive. Time Machine makes automatic backups of everything so you can recover individual files or your entire system from your backups.
Other backup methods
Store content in iCloud
iCloud lets you store and access your photos, documents, music, and other files in the cloud. iCloud comes with 5 GB of free storage, and you can upgrade your storage any time.
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 Sierra 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.