Time Machine can appear stuck on “Preparing backup…” for several reasons, including a large first backup, recently changed files, an interrupted backup, low storage, or a problem with the backup disk. In many cases, the process is normal and needs more time. If the status does not change for an unusually long period, use the steps below to identify and fix the cause.
Quick Answer
First, make sure the backup disk is connected, awake, and has enough free space. If Time Machine remains on “Preparing backup…” for hours without progress, stop the backup from the Time Machine menu, restart your Mac, reconnect the disk, and try again.
Why Time Machine Gets Stuck on “Preparing Backup”
The preparation stage is when Time Machine determines which files need to be copied. It may take longer than expected when:
- This is the first backup or the first backup after a major change.
- You recently moved, renamed, or deleted many files.
- macOS is indexing the disk with Spotlight.
- An earlier backup was interrupted.
- The backup disk is nearly full or has file-system errors.
- A large folder, virtual machine, photo library, or developer project changed.
- The Mac or backup disk went to sleep during a previous backup.
- Network Time Machine is being used over Wi-Fi.
- Time Machine is checking local snapshots before starting.
A backup can legitimately remain in the preparation stage for some time. The amount of time depends on the number of files, the speed of the Mac and backup disk, and whether the backup is connected directly or over a network.
Before You Stop the Backup
Before interrupting Time Machine, check whether it is actually making progress.
- Click the Time Machine icon in the menu bar. If you do not see it, open System Settings, select Control Center, find Time Machine, and choose Show in Menu Bar.
- Review the status message and estimated backup size.
- Check whether the backup disk activity light is blinking, if it has one.
- Wait longer if you recently created or changed a large amount of data.
Avoid shutting down the Mac, unplugging the backup disk, or forcing apps to quit while a backup may still be active. An interruption usually does not delete existing backups, but it can leave the current backup incomplete.
If the status has not changed for several hours and there is no apparent disk activity, stop the backup.
Stop and Restart Time Machine Safely
Stopping a stuck backup is the best first fix when the process clearly is not progressing.
- Click the Time Machine icon in the menu bar.
- Choose Stop This Backup.
- Wait for the status to change or for the backup disk to become idle.
- Restart your Mac from the Apple menu by choosing Restart.
- After the Mac starts, connect the backup disk directly if possible.
- Wait a few moments, then start a new backup from the Time Machine menu.
Save your work before restarting. Any unsaved changes in open apps could be lost if an app does not restore them correctly.
If Stop This Backup does not respond, close open applications normally and restart the Mac. If the Mac itself is unresponsive, hold the power button only as a last resort.
Check the Backup Disk and Its Available Space
Time Machine cannot complete a backup if the destination is disconnected, unavailable, or out of usable space.
Check the physical connection
- Connect the drive directly to the Mac instead of through a hub or dock.
- Try another USB, Thunderbolt, or USB-C cable.
- Try a different port.
- Confirm that the drive appears in Finder under Locations.
- If the drive has its own power adapter, make sure it is connected.
- Do not disconnect the drive while Time Machine is backing up.
For a network backup, verify that the Mac and backup device are connected to the same network. If possible, temporarily test with a directly connected drive.
Check free space
Open Disk Utility from Applications > Utilities, select the Time Machine disk, and review its available space. If the disk is almost full, Time Machine may need to remove older backups before creating a new one.
Do not manually delete folders inside a Time Machine backup. Those files are managed by Time Machine, and deleting them in Finder can damage the backup structure.
If your Mac is also low on internal storage, free up space before trying again. Local Time Machine snapshots can temporarily use space on the Mac. For help identifying and removing them, see how to delete local Time Machine snapshots that use Mac storage.
Check Time Machine Settings and Exclusions
A folder that is constantly changing can make preparation take much longer. Examples include virtual machines, video projects, temporary export folders, and some development directories.
- Open System Settings.
- Select General, then Time Machine.
- Click Options.
- Review the items under excluded locations.
If a large, constantly changing folder does not need to be backed up, add it to the exclusions list. Click the Add button, select the folder, and click Exclude.
Be careful when excluding folders. Anything excluded from Time Machine will not be available for restoration from that backup. Do not exclude important documents, photos, project files, or other irreplaceable data merely to make the backup finish faster.
You can also temporarily remove an exclusion if an important folder is missing from your backups. Start another backup afterward and confirm that the folder is included.
Check for an Incomplete Previous Backup
A failed or interrupted backup can cause Time Machine to spend a long time preparing the next one.
- Open System Settings.
- Select General, then Time Machine.
- Review the backup disk and recent backup status.
- Start a new backup after restarting the Mac and reconnecting the drive.
If Time Machine repeatedly reports that a backup is incomplete, the backup disk may have directory errors or communication problems. Do not erase the disk yet if it contains the only copy of your backups.
For additional protection, copy essential files to another disk or cloud storage before performing repair steps that could make an existing backup unavailable.
Run First Aid in Disk Utility
Disk Utility’s First Aid feature checks the disk’s file-system structure and attempts to repair certain errors.
- Stop the Time Machine backup if it is running.
- Open Disk Utility from Applications > Utilities.
- Select View > Show All Devices.
- In the sidebar, select the backup volume.
- Click First Aid, then click Run.
- If the volume is inside a container, run First Aid on the container and physical device as well, moving from the volume upward.
First Aid may temporarily unmount the disk. Ensure that no files on the drive are open and that no other backup or file transfer is using it. Do not disconnect the disk while First Aid is running.
If First Aid reports that it cannot repair the disk, do not erase it if you need the backups. A failing disk should be replaced, and important data should be recovered before it becomes inaccessible.
Restart Spotlight Indexing for the Backup Disk
Time Machine may take longer while macOS indexes a disk. If indexing appears stuck, you can remove and re-add the backup disk to Spotlight Privacy.
- Open System Settings.
- Select Siri & Spotlight.
- Scroll down and click Spotlight Privacy.
- Click the Add button.
- Select the Time Machine backup disk and click Choose.
- Select the disk in the privacy list and click the Remove button.
Adding the disk to Spotlight Privacy prevents Spotlight from searching it. Removing it from the list allows indexing again. This process does not erase the backup, but Spotlight may take time to rebuild its index afterward.
If you are unsure which disk to select, do not change this setting. A mistaken selection could prevent Spotlight from searching another drive you use regularly.
Disconnect Other Storage Devices Temporarily
Other external drives can sometimes slow down backup preparation or create additional disk activity.
- Stop the Time Machine backup.
- Eject external drives in Finder by clicking the Eject icon next to each drive.
- Disconnect nonessential storage devices, hubs, and card readers.
- Restart the Mac.
- Reconnect only the Time Machine disk.
- Start the backup again.
Do not disconnect a drive that contains files currently open in an app. Save those files and eject the drive properly first.
If the backup works with other devices disconnected, reconnect them one at a time to identify a possible cable, hub, or drive conflict.
Start a Backup in Safe Mode
Safe Mode starts macOS with a limited set of software and performs certain checks. This can help identify interference from third-party system software.
The procedure differs between Macs with Apple silicon and Intel-based Macs.
Apple silicon
- Shut down the Mac.
- Press and hold the power button until Loading startup options appears.
- Select a startup volume.
- Hold the Shift key and click Continue in Safe Mode.
- Sign in, connect the Time Machine disk, and try a backup.
Intel-based Mac
- Shut down the Mac.
- Turn it on and immediately hold the Shift key.
- Release the key when the login window appears.
- Sign in and try the backup.
If Time Machine works in Safe Mode, recently installed system utilities, antivirus software, disk tools, or other background software may be interfering. Restart normally and temporarily disable or uninstall recently added software according to its developer’s instructions.
Safe Mode is a diagnostic step, not a permanent solution. Some features may not work normally while the Mac is in Safe Mode.
Try a Different Backup Disk or Connection
If the same disk repeatedly remains on “Preparing backup…,” the disk, enclosure, cable, or connection may be the cause.
Test the following:
- A different cable.
- A different port.
- A direct connection instead of a hub.
- Another Mac-compatible backup disk, if available.
- A wired network connection for a network backup.
If a new disk works normally, preserve the old disk’s backups if possible and replace it. Do not assume a disk is healthy simply because it appears in Finder; a disk can mount while still developing read, write, or file-system problems.
Once a reliable backup is available, you can learn how to back up a Mac with Time Machine and set up a replacement destination.
When to Erase and Reformat the Backup Disk
Erasing the backup disk can resolve persistent file-system problems, but it permanently removes the backups stored on that disk.
Only consider erasing it when:
- You have confirmed that the existing backups are no longer needed, or
- You have another usable copy of the data and backups you want to keep.
Before erasing, open Time Machine and restore a few important files to verify that the backup is usable. You can also copy essential files elsewhere.
To erase the disk:
- Open Disk Utility.
- Select View > Show All Devices.
- Select the physical backup device in the sidebar.
- Click Erase.
- Choose a format appropriate for your Mac and Time Machine setup.
- Enter a name and click Erase.
The exact format options can vary by Mac and macOS configuration. If you are uncertain, do not erase the disk until you have confirmed the correct format and preserved any needed data.
Troubleshooting
Time Machine is stuck after a macOS update
Restart the Mac, reconnect the backup disk directly, and allow extra time for the first backup after the update. A system update can change or replace many files, resulting in a larger backup.
The backup starts but never finishes
Check for large changing folders, insufficient disk space, network interruptions, and disk errors. Temporarily disconnect other external devices and test a different cable or port.
Time Machine says the disk is unavailable
Reconnect the disk, verify that it appears in Finder and Disk Utility, and check its power supply. For a network disk, confirm the network connection and wake the backup device.
Time Machine repeatedly reports an incomplete backup
Run First Aid on the backup disk and test the disk with a different cable or port. If errors continue, treat the disk as unreliable and preserve important data before replacing it.
The backup disk does not appear at all
Open Disk Utility and choose View > Show All Devices. If it appears there but not in Finder, check whether the volume is mounted. If it does not appear in Disk Utility, test the cable, port, power adapter, and another computer if available.
You need files from an older backup
Do not erase or reformat the disk. Instead, use Time Machine to locate the files and restore them. You can also follow this guide to restore files from a Time Machine backup.
Frequently Asked Questions
How long should “Preparing backup…” take?
There is no fixed time. A first backup or one following major file changes can take much longer than a routine backup.
Is it safe to stop a Time Machine backup?
It is generally safe to use Stop This Backup, but do not unplug the disk while it is active.
Why does Time Machine prepare a backup every time?
Time Machine prepares each backup to determine what changed.
Final Thoughts
Time Machine usually becomes stuck on “Preparing backup…” because it is processing a large number of changes, dealing with an interrupted backup, or encountering a disk or connection problem.