How to Set Up Time Machine to Back Up Your Mac

Time Machine is Apple's built-in backup system for Mac computers. It works quietly in the background, making copies of everything on your Mac every hour. If you accidentally delete a file, or if your hard drive fails, Time Machine can bring everything back — sometimes down to the exact version of a document you were working on a week ago.

To use Time Machine, you need an external hard drive. The drive should have at least twice the storage capacity of your Mac's internal drive. For example, if your Mac has 512 gigabytes of internal storage, get a 1 or 2 terabyte external drive. These drives are affordable — a 2TB external drive costs $60 to $90 at most electronics stores or on Amazon.

When you plug in a new external drive, your Mac may automatically ask if you want to use it for Time Machine. If that prompt appears, click "Use as Backup Disk" and you are done with the initial setup. If it does not appear, go to System Settings (the gear icon in your Dock), click General, then Time Machine. Click "Add Backup Disk" and choose your external drive.

The first backup will take several hours — sometimes overnight — depending on how much is on your Mac. Leave your Mac plugged in, connected to the external drive, and let it run. After that first backup completes, Time Machine backs up automatically every hour when the drive is connected. It keeps every hourly backup for the past 24 hours, every daily backup for the past month, and every weekly backup until your drive fills up. Then it removes the oldest backups to make room.

To restore a specific file, click the Time Machine icon in your menu bar (the clock with an arrow) and choose "Enter Time Machine." You will see your Mac's desktop floating in a timeline — use the arrows to go back in time to when the file existed, click on it, and press Restore.

To restore your entire Mac after a hardware failure, hold Option+Command+R when starting up your Mac to access macOS Recovery, then choose Restore from Time Machine Backup.

Quick Tip: leave your external drive plugged in whenever your Mac is at home. Time Machine only backs up when the drive is connected — a drive that stays in a drawer does not help.