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Fix a Mac that has startup disk full

We'll free space on the startup disk by clearing Trash, caches, and large files.

Troubleshooting · Home maintenance
10–30 min
Step 1 of 6

Quick triage — pick your path

Quick triage — pick your path

Choose the option that matches what you see. You can jump straight to that section.

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Steps

Goal: Free space on the startup disk by clearing Trash, caches, and large files.

  • Empty Trash and clear your Downloads folder. These often hold gigabytes.
  • Good: Enough space freed. You are done.
  • Bad: Still full. Proceed to Optimize Storage.

Quick cleanup

Goal: Free space quickly with Optimize Storage.

  • Empty Trash. Open Downloads, delete or move large files. About This Mac, Storage, Manage—remove old iOS backups, empty Trash.
  • Good: Several GB freed.
  • Bad: Still need more. Proceed to Clear caches.

Find large files

Goal: Identify what is using space on the startup disk.

  • About This Mac, Storage, Manage. Review large files. Or in Finder, search by size. Delete or move large videos, installers, backups.
  • Good: Space freed.
  • Bad: No large files or cannot delete. Proceed to Clear caches.

Clear caches

Goal: Remove browser and app caches from the startup disk.

  • Clear Safari or Chrome cache. Delete ~/Library/Caches for apps you no longer use.
  • Good: Often 1–5 GB freed.
  • Bad: Uninstall apps or move data to external drive.

When to get help

  • If the startup disk still reports full after cleanup, run First Aid in Disk Utility.
  • For long-term relief, use an external drive or upgrade internal storage.

Verification

  • The startup disk shows increased free space in About This Mac, Storage.
  • You can save new files and install apps without “startup disk full” errors.
  • Trash is emptied.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Trash and Downloads Empty Trash; clear Downloads folder.
  2. Optimize Storage Use About This Mac, Storage, Manage; remove iOS backups.
  3. Caches and apps Clear browser cache; delete app caches; uninstall unused apps.
  4. Move data and snapshots Move large files to external drive; delete Time Machine local snapshots.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Mac model and startup disk size:
  • Free space before and after:
  • Largest folders or files found:

Have you emptied Trash and cleared Downloads?

These often hold gigabytes with minimal effort.

Empty Trash. Open Downloads, delete or move large files. Good: space freed. Bad: still full—use Optimize Storage.

Yes, enough No, need more

You can change your answer later.

Have you used Optimize Storage?

Optimize Storage removes iOS backups and suggests large files.

About This Mac, Storage, Manage. Remove old iOS backups. Empty Trash. Review large files. Good: several GB freed. Bad: still full—clear caches, uninstall apps.

Yes No

You can change your answer later.

Have you cleared browser and app caches?

Caches can use several GB on the startup disk.

Clear Safari or Chrome cache. Delete ~/Library/Caches for unused apps. Good: space freed. Bad: still full—uninstall apps, move data.

Yes No

You can change your answer later.

Have you uninstalled unused apps?

Large apps can use 10–50 GB each on the startup disk.

Drag unused apps to Trash. Games and creative suites are often large. Good: space freed. Bad: still full—move data to external drive.

Yes No

You can change your answer later.

Startup disk has enough free space

The startup disk has sufficient free space. Consider setting up regular cleanup or moving large files to an external drive.

Done

Consider more options

Move photos/videos to external drive or iCloud. Delete Time Machine local snapshots (tmutil deletelocalsnapshots). Run First Aid in Disk Utility. Consider upgrading storage.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why does my Mac startup disk keep filling up?
The startup disk holds macOS and your data. Trash, Downloads, browser cache, iOS backups, and large apps fill it. Optimize Storage and clearing caches usually free the most space.
Is it safe to delete cache files on the startup disk?
Yes. ~/Library/Caches holds temporary files. Apps recreate them. Clearing cache is safe but you may need to log in again to some apps.
What is the startup disk?
The disk that contains macOS and from which the Mac boots. Usually the internal SSD. Must have free space for the system to work.

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