How to free up disk space on a Mac when the startup disk is full

Summary

This guide helps you troubleshoot and resolve: How to free up disk space on a Mac when the startup disk is full. Follow the steps below to fix the issue.

Common Causes

When your Mac's startup disk fills up, performance can slow down, apps may refuse to open, and you might see an "Your disk is almost full" warning. This guide walks you through practical ways to identify what is consuming your storage and safely reclaim space on macOS.

Quick Check: Where Is Your Space Going?

Before deleting anything, it helps to see exactly what is using your storage. macOS includes a built-in storage manager that breaks your usage down by category.

1. Click the Apple menu and select System Settings.
2. Click General in the sidebar, then select Storage.
3. Wait for the storage bar to finish calculating, then review the colour-coded segments (Applications, Documents, System Data, and so on).
4. Hover over each segment to see the size and a brief description.

Clear System and User Caches

Caches speed up your Mac, but over time they can balloon to many gigabytes. Clearing them is safe — macOS will rebuild them as needed.

Clear System Caches

1. Open Finder and choose Go > Go to Folder from the menu bar.
2. Type ~/Library/Caches and press Return.
3. Drag the contents of the folders inside to the Trash, then empty it.

Clear Browser Caches

• Safari: Open Safari, choose Safari > Settings > Advanced, then enable Show Develop menu. From the Develop menu, choose Empty Caches.
• Chrome: Choose Chrome > Clear Browsing Data, select Cached images and files, then click Clear data.
• Firefox: Choose Firefox > Settings > Privacy & Security, then click Clear Data.

Find and Remove Large Files

The built-in storage manager makes it easy to locate oversized files you may have forgotten about.

1. Open System Settings > General > Storage.
2. Click Files (or Documents on older macOS versions).
3. Sort by Size using the column header.
4. Select files you no longer need and click Delete.

For a deeper search, use Finder:

1. Press Command + F to open a Find window.
2. Click the Kind dropdown and choose Other, then type File Size.
3. Set the size filter to is greater than 500 MB (adjust as needed).
4. Switch the search location to This Mac using the bar at the top.
5. Review the results and delete anything you no longer need.

Empty the Trash

Deleted files only free up space once the Trash is emptied. macOS does not do this automatically.

1. Click the Trash icon in the Dock.
2. If you spot files you want to keep, drag them out first.
3. Right-click the Trash icon and choose Empty Trash.
4. Confirm by clicking Empty Trash in the dialogue box.

Remove Old Downloads

The Downloads folder is a common culprit for hidden storage consumption.

1. Open Finder and click Downloads in the sidebar.
2. Switch to List view using Command + 2.
3. Click the Date Added column header to sort, then look for old installers, DMG files, and ZIP archives.
4. Drag unwanted files to the Trash, then empty it.

Uninstall Apps You No Longer Use

Simply dragging an app to the Trash does not always remove all of its supporting files.

1. Open Finder and click Applications in the sidebar.
2. Right-click any app you no longer need and choose Move to Trash.
3. For apps installed from the App Store, open Launchpad, hold Option, and click the X on the app icon.
4. Empty the Trash when finished.

Manage iCloud and Optimise Storage

If you use iCloud, you can offload older files from your Mac to free up local space.

1. Open System Settings and click your Apple ID (your name at the top).
2. Click iCloud, then click Drive.
3. Enable Optimise Mac Storage. Files stored only in iCloud will appear as placeholders on your Mac and download on demand.

Clear Mail Attachments and Old Messages

Mail and Messages can quietly accumulate large attachments over the years.

Mail

1. Open Mail and choose Mailbox > Erase Junk Mail.
2. Choose Mailbox > Erase Deleted Items, then select each account and click Erase.
3. For older messages with large attachments, use Mail > Settings > Accounts > Account Information and adjust the Download attachments setting to Recent only or None.

Messages

1. Open Messages and choose Messages > Settings > General.
2. Tick Keep messages and choose 30 days or 1 year.
3. Click Delete to confirm the cleanup.

Troubleshooting

The storage bar still shows full after deleting files

• Remember to empty the Trash — deleted files do not release space until then.
• Restart your Mac. macOS occasionally holds onto purged data until a reboot.
• Check System Settings > General > Storage again after a few minutes — the calculation can take time to refresh.

Purgeable storage will not shrink

macOS marks some files as "purgeable" when it believes they can be regenerated, such as Time Machine local snapshots. To force a cleanup:

1. Open Terminal (found in Applications > Utilities).
2. Type tmutil thinlocalsnapshots / 1000000000000 4 and press Return.
3. Wait for the command to complete, then check your storage again.

"System Data" is unusually large

System Data includes caches, logs, app extensions, and macOS itself. If it is consuming far more than expected, try booting into Safe Mode (restart and hold the Shift key), which clears some system caches automatically. If the issue persists, consider using a dedicated tool such as DaisyDisk to visualise what is contributing to System Data, or contact Apple Support for further assistance.

Still Having Issues?