Time Machine Error 11
Apple macOS
Severity: ModerateWhat Does This Error Mean?
Time Machine Error 11 means the backup could not be completed because of a problem writing to the backup drive. This error often appears as 'Backup Failed: Time Machine could not complete the backup.' It is usually caused by file system errors on the backup drive, a loose cable, or the backup drive being disconnected mid-backup.
Affected Models
- MacBook Air
- MacBook Pro
- iMac
- Mac Mini
- Mac Studio
Common Causes
- The backup drive was disconnected or went to sleep while the backup was still running
- The backup drive has file system errors that are preventing writes
- The USB or Thunderbolt cable connecting the backup drive is faulty
- A specific file on your Mac is locked or has permissions that prevent Time Machine from reading it
- The Time Machine backup image (sparsebundle file) has become corrupted
How to Fix It
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Eject and reconnect the backup drive. Click the drive on your Desktop, press Command + E to eject it, unplug the cable, wait 10 seconds, and reconnect.
A brief connection issue can cause Error 11. Reconnecting the drive often allows the next backup to complete successfully.
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Run First Aid on the backup drive. Open Disk Utility (Applications > Utilities). Select your backup drive on the left and click First Aid.
File system errors on the backup drive are a common cause of Error 11. First Aid repairs these errors.
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Prevent the backup drive from sleeping. Go to System Settings > Battery (or Energy Saver on older Macs). Check 'Prevent hard disks from sleeping when possible.'
If the drive spins down while a backup is running, Time Machine loses connection mid-write and Error 11 occurs.
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Delete the last incomplete backup. Open your backup drive in Finder. Inside the Backups.backupdb folder, look for a folder with today's date and a .inProgress suffix. Delete it.
An incomplete backup marked .inProgress can block future backups. Deleting it allows Time Machine to start fresh.
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Start a new Time Machine backup. If errors persist, open Time Machine preferences, remove the current backup destination, and add it back. This starts a new backup without the corrupted history.
Warning: starting fresh deletes your old backup history. Only do this after trying all other steps.
When to Call a Professional
If the backup drive is making unusual noises (clicking, grinding), stop using it immediately. That indicates physical hardware failure — take it to a data recovery specialist if you need files off it. For a healthy drive with software errors, all the fixes below can be done at home.
Frequently Asked Questions
Is my data at risk when Time Machine shows Error 11?
Your original files on your Mac are fine — the error only affects the backup copy. However, if you rely on Time Machine as your only backup and it keeps failing, you are at risk. Fix the error promptly so your backups resume protecting your data.
How often should Time Machine back up?
Time Machine automatically backs up every hour when the backup drive is connected. It also keeps daily backups for the past month and weekly backups for all previous months. You cannot change the hourly frequency without third-party apps.
What is a .inProgress backup and is it safe to delete?
A .inProgress file is a backup that was interrupted before it finished. Time Machine tries to use it to resume the backup, but sometimes a corrupted .inProgress file blocks all future backups. Deleting it is safe — Time Machine will start a fresh backup without losing your previous completed backups.