How to set up and use macOS Time Machine to back up to an external drive

Backup & Storage KB-247

Summary

This guide helps you troubleshoot and resolve: How to set up and use macOS Time Machine to back up to an external drive. Follow the steps below to fix the issue.

Quick Tip: Need immediate assistance? 💻 Open a Ticket

Common Causes

macOS Time Machine is a built-in backup tool that automatically saves copies of your files, apps, and system settings to an external drive. Once configured, Time Machine runs in the background, keeping hourly, daily, and weekly backups so you can recover individual files or restore your entire Mac after a hardware failure or accidental deletion. This guide walks you through selecting a compatible drive, setting up Time Machine, and restoring data when needed.

Before You Begin

You'll need an external drive with enough storage to hold multiple backups. As a general rule, your backup drive should be at least twice the size of your Mac's internal storage. For example, a 500GB Mac should use a 1TB or larger external drive.

Drive Compatibility

USB, Thunderbolt, or Network-attached (NAS) drives are all supported
For direct connections, drives formatted as APFS or Mac OS Extended (Journaled) work best
For network (SMB) backups, the drive must be formatted as Mac OS Extended (Journaled)
If the drive is currently formatted for Windows (NTFS or exFAT), Time Machine will offer to reformat it, which erases all existing data on the drive

If you only want to back up specific files such as photos, see our guide on How to backup photos to external drive.

Set Up Time Machine

Connect your external drive to your Mac. If prompted with a dialog asking what to do with the drive, click Don't Use — Time Machine will configure it separately.
Open System Settings from the Apple menu.
Click General in the sidebar, then select Time Machine.
Click Add Backup Disk.
Select your external drive from the list and click Set Up Disk.
If asked, choose whether to erase the drive:
- Select Erase if the drive is new or you don't need its current contents.
- Select Don't Erase only if the drive is already formatted correctly and contains data you wish to keep.
Choose your backup options:
- Back Up Automatically — keep this enabled so Time Machine runs on its own schedule.
- Show in Menu Bar — adds a Time Machine icon to the menu bar for quick access.
Click Done. Time Machine will begin its first backup immediately, which may take several hours depending on the amount of data.

The first backup is usually large and slow. Subsequent backups are much faster because Time Machine only copies files that have changed.

Using Time Machine

Back Up Manually

If you want to start a backup outside the automatic schedule:

Click the Time Machine icon in the menu bar (clock with an arrow).
Select Back Up Now.

Alternatively, open System Settings > General > Time Machine and click the backup icon next to your drive.

Recover Lost Files

Open Finder and navigate to the folder that originally contained the file.
Click the Time Machine icon in the menu bar and choose Enter Time Machine.
Use the timeline on the right edge of the screen or the arrow buttons to browse available backup dates.
Select the file or folder you wish to restore.
Click Restore to copy the selected version back to its original location.

Restore Your Entire Mac

If your Mac's startup drive has failed or been replaced, you can restore everything from your Time Machine backup during macOS setup:

Connect your Time Machine drive to the Mac.
Power on the Mac and hold Command (⌘) + R during startup to enter macOS Recovery.
Select Restore From Time Machine Backup from the macOS Utilities window.
Follow the prompts to choose your backup drive, the backup date, and the destination disk.

Restoring from Time Machine overwrites the destination drive. Make sure you select the correct disk and back up any current data before proceeding.

Troubleshooting

Time Machine Is Not Backing Up

Confirm the external drive is connected and powered on.
Open System Settings > General > Time Machine and verify the drive is listed and selected.
Check that the drive has sufficient free space. Time Machine purges older backups automatically, but a nearly full drive can stall the process.
Restart your Mac and reconnect the drive if the backup appears stuck.

Drive Not Appearing in Time Machine

Try a different USB or Thunderbolt port, or test the drive on another Mac to rule out a hardware fault.
Open Disk Utility (found in Applications > Utilities) and check whether the drive is mounted.
If the drive shows as read-only or unformatted, back up its contents elsewhere and reformat it as APFS using Disk Utility's Erase function.

Backup Is Very Slow

Use a direct connection rather than a USB hub.
For large initial backups, leave the Mac plugged in and connected to power overnight.
Avoid running heavy applications during the first backup, as they can slow the process further.

Need to Start Over With a New Drive

Open System Settings > General > Time Machine.
Select the current backup disk and click Remove Backup Disk.
Disconnect the old drive and connect the new one.
Click Add Backup Disk and follow the setup steps again.

Removing a backup disk does not erase the data on that drive. You can still use it as an archive or re-add it later.

Best Practices

Keep your backup drive connected regularly so Time Machine can maintain its schedule.
Periodically check that backups are completing successfully by clicking the Time Machine icon in the menu bar.
Consider using a second backup drive stored offsite for added protection against theft, fire, or flood.
Replace your backup drive every few years, as with any storage device, to reduce the risk of drive failure.

If you continue to experience issues with Time Machine or need help choosing a suitable backup drive for your setup, open a ticket and our team will be happy to assist.

Still Having Issues?

Need more help? If the issue persists after trying these steps, please open a support ticket and our team will assist you.

💻 Open a Ticket