How to fix macOS Time Machine backups failing or getting stuck on 'Preparing Backup'

Summary

This guide helps you troubleshoot and resolve: How to fix macOS Time Machine backups failing or getting stuck on 'Preparing Backup'. Follow the steps below to fix the issue.

Common Causes

Time Machine is the built-in backup solution for macOS. When backups fail or become stuck on the Preparing Backup screen, your business data may not be protected. This guide provides steps to resolve common Time Machine issues on Mac computers used by small business and home office users across Australia.

Quick Fix Steps

Try these simple steps first before moving to more detailed troubleshooting.

1. Restart your Mac by clicking the Apple menu > Restart.
2. Ensure your backup drive is connected directly to your Mac, not through a USB hub.
3. Check that your Mac is connected to the same network as your Time Capsule or NAS device if backing up wirelessly.
4. Open System Settings, go to General > Time Machine, and verify the backup disk is selected.

Detailed Instructions

Check Backup Disk Connection

1. Disconnect your external backup drive from your Mac.
2. Wait 10 seconds, then reconnect the drive to a different USB or Thunderbolt port.
3. Open Finder and confirm the backup drive appears in the Locations sidebar.
4. Open System Settings > General > Time Machine and ensure the correct disk is selected.

If you use a network backup device, ensure your Mac and the backup device are connected to the same Wi-Fi network or Ethernet switch.

Restart Time Machine Service

1. Click the Apple menu > System Settings.
2. Select General in the sidebar, then click Time Machine.
3. Click the toggle switch to turn Time Machine Off, wait 30 seconds, then turn it On again.
4. Click Back Up Now to test if the backup proceeds past Preparing Backup.

Check Available Disk Space

1. Open Finder and click your backup drive in the sidebar.
2. Press Command + I to view Get Info.
3. Confirm there is sufficient free space on the backup drive. Time Machine generally requires at least as much free space as the data being backed up.
4. If the drive is full, delete old backups or connect a larger drive.

Troubleshooting

Backup Stuck on Preparing Backup

1. Click the Time Machine icon in the menu bar and select Skip This Backup.
2. Open System Settings > General > Time Machine.
3. Click Remove Backup Disk, then click Add Backup Disk and reselect your drive.
4. Click Back Up Now to start a fresh backup.

Do not force shutdown your Mac while Time Machine is actively writing data, as this can corrupt the backup database.

Time Machine Backup Fails with Error

1. Open Finder, go to Go > Go to Folder, and enter /Library/Logs/DiagnosticReports/.
2. Look for Time Machine-related error logs to identify the specific failure point.
3. Open Disk Utility from Applications > Utilities.
4. Select your backup drive in the sidebar and click First Aid to check and repair disk errors.
5. If First Aid reports errors it cannot repair, back up any critical data from the drive and reformat it using APFS or Mac OS Extended (Journaled).

Exclude Large or Unnecessary Files

1. Open System Settings > General > Time Machine.
2. Click Options.
3. Click the + button to add folders you do not need backed up, such as large video files or temporary caches.
4. Click Done, then run Back Up Now.

Excluding large, non-critical folders can significantly reduce backup time and prevent the Preparing Backup stage from taking hours.

If Time Machine continues to fail after following these steps, Open a Ticket with 220 Internet Services for further assistance.

Still Having Issues?