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macOS "Your disk is almost full": what it means and how to fix it

Short answer

"Your disk is almost full" means your Mac's startup disk is nearly out of free space. That can cause slowdowns, failed saves and blocked macOS updates. Open Apple menu > System Settings > General > Storage (on macOS 12 or earlier: About This Mac > Storage). Find the biggest category, click its (i) button, delete what you don't need, then empty the Trash.

What this message means

macOS shows this alert when free space on the startup disk (usually "Macintosh HD") gets low. macOS needs free space for virtual memory, caches, app updates and system updates. When space runs out, apps can freeze, files may fail to save and updates will refuse to install. macOS already treats "purgeable" space (iCloud files it can re-download, old caches, Time Machine local snapshots) as available and clears it automatically. So if you see this warning, the disk is genuinely short of space even after that. You need to delete, move or offload real data. A common rule of thumb is to keep 10 to 15 percent of the disk free.

Common causes

CauseHow to tell
Large personal files, usually in Downloads, Desktop, Documents or MoviesIn System Settings > General > Storage, Documents is one of the largest bars. Clicking its (i) button shows big files such as videos, disk images (.dmg) or old installers.
A large Photos or music library stored on the MacPhotos, or Music/TV, shows tens or hundreds of GB in the Storage list. In Finder, the "Photos Library" file in your Pictures folder is very large.
Old iPhone or iPad backupsStorage shows an "iOS Files" category. Clicking its (i) button lists device backups, often 5 to 100 GB each, some from phones you no longer own.
Oversized System Data (caches, logs, Time Machine local snapshots, developer tools, virtual machines)System Data (called "Other" on older macOS) takes a large share of the Storage bar, and deleting your own files hardly changes it. Running tmutil listlocalsnapshots / in Terminal lists several snapshots.
Files you deleted are still in the Trash, or Mail has piled up attachmentsThe Trash icon in the Dock shows paper in it, or Storage lists Trash and Mail with several GB each.

How to fix it

1. See what is using the space and use the built-in recommendations

macOS Ventura 13 and later. On macOS 12 or earlier, use Apple menu > About This Mac > Storage > Manage.

  1. Choose Apple menu > System Settings, then click General in the sidebar and click Storage.
  2. Wait for the coloured bar to finish calculating. Hover over each colour to see which category is largest.
  3. Under Recommendations, turn on Empty Trash Automatically (deletes items that have been in the Trash for more than 30 days). If you use iCloud, you can also turn on Store in iCloud and Optimize Storage.
  4. In the list below, click the (i) button next to the biggest category, for example Documents or Applications.
  5. Sort by size, select files or apps you no longer need, and click Delete. The Storage page updates as you go.

2. Empty the Trash and clear the Downloads folder

  1. In Finder, press Option-Command-L to open Downloads.
  2. Choose View > as List, then click the Size column header to sort the largest files to the top.
  3. Drag old installers (.dmg, .pkg), zip files and videos you no longer need to the Trash.
  4. Choose Finder > Empty Trash, or press Shift-Command-Delete. Space is not freed until the Trash is emptied.
  5. If you use Photos, open it and choose Recently Deleted in the sidebar, then click Delete All. Deleted photos otherwise stay there for 30 days.

3. Delete old iPhone and iPad backups

  1. Go to System Settings > General > Storage and click the (i) button next to iOS Files.
  2. Select backups of devices you no longer own, or older duplicates, and click Delete.
  3. Or: connect the device, select it in the Finder sidebar, click Manage Backups, select a backup and click Delete Backup.
  4. Keep at least one current backup of any device you still use. Alternatively, back it up to iCloud instead of the Mac.

4. Move large media libraries to an external drive or iCloud

  1. Connect an external drive formatted as APFS or Mac OS Extended.
  2. For Photos: quit Photos, drag the Photos Library from your Pictures folder to the external drive, then hold Option while opening Photos and choose the moved library.
  3. Once you confirm the moved library opens and is complete, delete the original from your Pictures folder and empty the Trash.
  4. Alternatively, in Photos choose Photos > Settings > iCloud and select Optimize Mac Storage. This keeps full-size originals in iCloud (needs enough iCloud storage).
  5. Move large video projects or iMovie/Final Cut libraries the same way.

5. Clear Time Machine local snapshots

Macs with Time Machine turned on. The Settings path is for macOS Ventura 13 and later. On older versions, uncheck Back Up Automatically in System Preferences > Time Machine.

  1. Open System Settings > General > Time Machine, click Options, and set Backup Frequency to Manually. Click Done.
  2. Wait a few minutes. macOS deletes the local snapshots on its own.
  3. To check or delete manually, open Terminal (Applications > Utilities) and run: tmutil listlocalsnapshots /
  4. Delete a specific snapshot with: sudo tmutil deletelocalsnapshots 2026-09-30-101500 (use a date shown in the list), then enter your Mac password.
  5. Set Backup Frequency back to Automatically Every Hour afterwards so backups continue to your external drive.

6. Start in safe mode to clear system caches

Useful when the disk is so full that apps or a macOS update will not run. Steps differ for Apple silicon and Intel Macs.

  1. Apple silicon: shut down, then press and hold the power button until "Loading startup options" appears. Select your startup disk, hold Shift and click Continue in Safe Mode.
  2. Intel: restart and immediately press and hold Shift until the login window appears.
  3. Log in. Starting in safe mode clears some system caches, which can free enough space to finish an update or delete files.
  4. Restart normally to leave safe mode, then check System Settings > General > Storage again.

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Still not fixed?

If System Data is still huge after these steps, restart the Mac and wait 10 to 15 minutes. macOS often recalculates System Data late, and it can drop after the restart. Then check for known space hogs: virtual machines (Parallels, UTM), Docker Desktop's disk image (Docker > Settings > Resources), Xcode data in ~/Library/Developer, and cloud folders set to keep files offline (Dropbox, OneDrive, Google Drive). If the warning keeps coming back with plenty of space shown, or the Mac won't start because the disk is full, contact Apple Support or book an Apple Store Genius Bar appointment. A disk that is always tight is also a sign you may need an external drive or a Mac with more storage.

Questions people ask

Is it safe to delete System Data on a Mac?

Don't delete files from system folders by hand. Most System Data is caches, logs and Time Machine snapshots that macOS manages itself. Deleting local snapshots, iPhone backups and large app data (VMs, Docker, Xcode) through their own settings is safe.

What is purgeable space on a Mac?

Purgeable space is data macOS can remove automatically when space is needed, such as iCloud files that can be downloaded again, old caches and local Time Machine snapshots. macOS counts it as available, so you don't need to clear it yourself.

How much free space should a Mac have?

Apple does not publish a fixed number. A common rule of thumb is to keep 10 to 15 percent of the disk free, plus extra before a major macOS upgrade, which can need 20 GB or more.

Why does my Mac still say the disk is full after I deleted files?

The files are probably still in the Trash or in Photos' Recently Deleted album. Empty both. If you deleted a Time Machine-backed file, a local snapshot may hold it until the snapshot is removed.

Can I turn off the "Your disk is almost full" warning?

No, macOS has no setting to disable it. The warning only stops once enough space is free, and ignoring it risks failed saves and blocked updates.

Sources

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