Do you need to reconfigure Time Machine to use a new external hard drive? If you read my Tech Tips regularly then you’ll recall that I strongly recommend that everybody setup automatic and redundant systems to backup their Mac. If you use Time Machine to backup your Mac to an external hard drive then you will eventually need to replace the external drive when it dies. Here are instructions on how to reconfigure Time Machine to backup to a different hard drive.

If your Mac is using macOS 12 Monterey or older, use the instructions listed in Section 1

If your Mac is using macOS 13 Ventura or newer, jump to Section 2.

Section 1 – if your Mac is running macOS 12 Monterey or older

• Click on the Apple menu and select System Preferences
• Click on Time Machine
• Click the Select Disk button. [Note: If your Mac is configured to backup to 2 or more backup drives then the button will be labeled Add/Remove Backup Disk.]
• In the Backup Disks section, click on the name of the external hard drive that has died and click the Remove Disk button.
• In the Available Disks section, click on the name of the external hard drive that is replacing the dead hard drive then click the Use Disk button.
• You should see a prompt asking if you want to replace your current drive or use both drives. In this case, you want to replace it.   [Important: Since most new hard drives come setup (formatted) as PC hard drives. Time Machine may inform you that it needs to erase (reformat) this hard drive so it can be used as a Mac hard drive. If you see this prompt, let this occur.]
• Click the red dot to close System Preferences.
• Within a couple of minutes, Time Machine will initiate a backup to this new hard drive. Let this backup run in the background. It’ll likely take many hours to finish since it needs to backup everything on your Mac.

Section 2 – if your Mac is running macOS 13 Ventura or newer

• Click on the Apple menu and select System Settings.
• Click on General.
• Click on Time Machine.
• Click on the name of your current backup hard drive to select it, then click the minus sign (-) button to remove this drive.
• Type in your computer user account password and then click the Modify Settings button.
• Click the Forget Destination button to fully remove this drive.
• Click the Add Backup Disk button (Note: if you already have a second drive listed then you’ll click the plus sign button, instead, to add an additional drive. This is an uncommon situation.)
• Select your new USB external hard drive from the list of drives then click the Set Up Disk button. Important Note: Please be aware that this set up process may erase your new drive in order to change the hard drive’s formatting.
• Click the red dot to close System Settings and Time Machine settings.
• Within a couple of minutes, Time Machine will initiate a backup to this new hard drive. Let this backup run in the background. It’ll likely take many hours to finish since it needs to backup everything on your Mac.