To keep your files safe, it’s important to back up your iMac regularly. The easiest way to back up is to use Time Machine—which is built into your iMac—with an external storage device connected to your iMac. Time Machine can also back up your Mac contents to supported network volumes. For a list of devices supported by Time Machine, see the Apple Support article Time Machine:Automatically backs up your entire iMac, including system files, apps, accounts, preferences, music, photos, movies, and documents.Remembers how your computer looked on any given day, so you can revisit your iMac as it appeared in the past or retrieve an older version of a document.Lets you restore your entire system from a Time Machine backup. So if anything happens to your iMac, your files and settings are safe and sound.Learn more. See Back up your files with Time Machine in the macOS User Guide.
Time Machine:
Automatically backs up your entire iMac, including system files, apps, accounts, preferences, music, photos, movies, and documents.
Remembers how your computer looked on any given day, so you can revisit your iMac as it appeared in the past or retrieve an older version of a document.
Lets you restore your entire system from a Time Machine backup. So if anything happens to your iMac, your files and settings are safe and sound.
Learn more. See Back up your files with Time Machine in the macOS User Guide.