Set up Time Machine to back up your Mac

Why it happens

Time Machine can't save anything until you give it a backup disk. Once it has one, it keeps hourly backups for a day, daily ones for a month and weekly ones until the disk is full. iCloud syncs your files but isn't a full backup of your Mac, so a Time Machine drive is worth having.

How to fix it

1. Get an external drive about twice the size of your Mac's storage. You can check how much storage your Mac has in General > About. Plug the drive straight into your Mac, not through a hub.

2. Open the Apple menu, choose System Settings, click General, then Time Machine, and click Add Backup Disk.

   macOS 26 Tahoe General›Time Machine›Add Backup Disk

   macOS 27 Golden Gate General›Time Machine›Add Backup Disk…

3. Select your drive and click Set Up Disk. To protect the backup with a password, tick Encrypt Backup and choose one. Store that password somewhere safe, because the backup can't be opened without it.

4. If your Mac says it needs to erase the drive, stop and copy off anything you want to keep first. Erasing deletes everything on that drive.

5. Leave the drive plugged in. The first backup can take hours. After that, backups are quick and run every hour by themselves.

The button is called Add Backup Disk on macOS 26 and Add Backup Disk… on macOS 27. It does the same thing in the same place.

Still not fixed?

1. Drive not in the list? Plug it in directly, make sure it's switched on, and check it shows under Locations in the Finder sidebar. If it still doesn't appear, open Disk Utility, select the drive and run First Aid.

   Disk Utility›First Aid

2. Backing up to a network drive or a shared folder on another Mac? Click Add Backup Disk, choose the network share and enter its account details when asked.

3. To see when the last backup ran, or to start one now, tick Time Machine under Menu Bar Controls in Menu Bar settings. Then click its icon in the menu bar and choose Back Up Now.

   Menu Bar›Menu Bar Controls›Time Machine

4. On a MacBook, Time Machine skips backups on battery unless you turn on Back up on battery power under Options….

   General›Time Machine›Options…›Back up on battery power

5. If backups keep failing or First Aid reports errors on the backup drive, the drive itself may be failing. That's a hardware problem: replace the drive, or contact its maker or a repair shop. For trouble with your Mac itself, contact Apple Support.