Free Up Disk Space & Remove Hidden Storage on macOS 15
This article explains how to free up disk space and remove hidden storage on macOS 15 (Sequoia). You’ll learn where the “hidden� space goes, which built-in tools to use, and how to safely delete large system caches and other files that aren’t obvious in Finder.
Why Does macOS 15 Show Less Free Space Than Expected?
When you check storage in System Settings > General > Storage, you may see a gray “System Data� category that eats up tens or even hundreds of gigabytes. This isn’t a single folder—it’s a catch-all for caches, logs, temporary files, Time Machine local snapshots, and other system files that macOS doesn’t label individually. The amount can grow over time, especially if you use apps that cache a lot of data (e.g., video editors, browsers, or Xcode).
Another hidden consumer is “purgeable space.� macOS marks files as purgeable when they can be deleted automatically (like iCloud-optimized photos or emptied Trash items). These files don’t show up in the regular file count, but they still occupy physical space until the system needs it.
What Actually Counts as “Hidden� Storage?
Hidden storage typically includes:
- System caches (in ~/Library/Caches and /Library/Caches) – app and system data that can be rebuilt.
- Logs (in ~/Library/Logs and /var/log) – daily and system logs, some of which are large.
- Time Machine local snapshots – stored on your startup disk if you have Time Machine enabled.
- App support files – some apps download large assets (e.g., fonts, maps, or game levels) that aren’t visible in the standard file browser.
- iOS backups and device backups – if you back up an iPhone or iPad to your Mac, those files live in ~/Library/Application Support/MobileSync.
- Old system files – from previous macOS updates, sometimes kept in a “Backups� or “Previous Systems� folder.
How to Check What’s Taking Up Space
macOS 15 includes a built-in storage management tool:
- Click the Apple menu and select System Settings.
- Go to General > Storage.
- You’ll see a bar chart showing categories like Applications, Documents, System Data, and more. Hover over a section to see its size.
- Click the i button next to a category to see recommendations (e.g., empty Trash, optimize storage, delete old iOS backups).
For a more granular view, you can use Finder’s “All My Files� or a third-party disk analyzer (like DaisyDisk or OmniDiskSweeper) that shows every file and folder size. These tools are especially useful for finding large files you forgot about.
How to Free Up Space Safely
Here are the most effective methods, in order of safety and impact:
- Empty the Trash – Right-click the Trash icon and select “Empty Trash.� Also check “Trash� in the Storage tab for large items.
- Delete old iOS backups – In Storage settings, click the “i� next to “iOS Files� and remove backups you no longer need.
- Clear system caches – You can manually delete files in ~/Library/Caches (your user caches) and /Library/Caches (system caches). Only delete files you’re sure are safe—most are just temporary data that apps recreate. Avoid deleting anything in /System/Library/Caches.
- Remove Time Machine local snapshots – If you have Time Machine enabled, local snapshots can accumulate. In Terminal, run
tmutil listlocalsnapshots /to see them, thentmutil deletelocalsnapshots <date>to delete specific ones. Or disable local snapshots entirely (not recommended if you use Time Machine). - Use the “Reduce Clutter� tool – In Storage settings, click “Reduce Clutter� to see large files, downloads, and unsupported apps.
- Optimize storage – Enable “Optimize Mac Storage� in iCloud settings to offload old files to iCloud and keep only recent ones locally.
Common Mistakes That Don’t Actually Free Much Space
Many people try these things and see little improvement:
- Deleting “Other� files – The “Other� category in older macOS versions was a mix of caches, logs, and app support. In macOS 15, it’s called “System Data.� Randomly deleting files from that category can break apps.
- Clearing browser cache – While this can free a few hundred MB, it’s rarely the big culprit. Modern browsers are efficient.
- Deleting system logs – Logs are small (usually a few hundred MB at most). Don’t bother unless you’re desperate.
- Using “Purgeable Space� as a magic fix – Purgeable space is automatically reclaimed when needed. You don’t need to delete it manually; the system will do it when you install a large app or update.
How to Prevent Hidden Storage from Piling Up
To keep your disk from filling up again:
- Regularly empty Trash – Set Finder to empty Trash automatically after 30 days (Finder > Settings > Advanced).
- Limit Time Machine local snapshots – If you don’t need them, disable local snapshots by turning off Time Machine and using a different backup strategy.
- Uninstall apps you don’t use – Apps like Xcode, Adobe Creative Cloud, and video editors can take up 10-30 GB each. Use the Storage tab to see app sizes and delete the ones you no longer need.
- Move large media to an external drive – Photos, movies, and music are often the biggest space hogs. Keep them on an external SSD or a NAS.
- Use iCloud Photo Library – This stores full-resolution photos in iCloud and keeps only optimized versions on your Mac.
Frequently Asked Questions
Why is “System Data� so large on my Mac?
System Data includes caches, logs, temporary files, and other system files. It can grow if you have many apps, especially ones that download large assets. You can reduce it by clearing caches and deleting old backups, but some of it is normal and will remain.
Is it safe to delete files in ~/Library/Caches?
Generally yes. These are temporary files that apps recreate. However, some apps may store important data there (e.g., unfinished downloads). To be safe, close all apps before deleting, and only delete the contents of subfolders, not the folders themselves.
Does emptying Trash permanently delete files?
Yes, after you empty the Trash, the files are no longer accessible through Finder. However, they may still be recoverable with specialized software until overwritten. For secure deletion, use Finder’s “Secure Empty Trash� option (if available) or a third-party tool.
Why does my Mac show less free space than the sum of all files?
Because of hidden system files, APFS snapshots, and purgeable space. The storage bar in System Settings shows categories, but not every file is counted in a category. The actual free space is what matters; the “purgeable� space will be reclaimed automatically.
Can I delete the “Backups� folder on my startup disk?
If you see a “Backups� folder (often from a previous macOS installation), you can delete it if you’re sure you don’t need the old system files. It’s usually safe to remove after you’ve been on the new version for a while. But check that it doesn’t contain important documents you might have forgotten.
What’s the easiest way to find large files?
Open Finder, press Command+Shift+G, type ~/Library, and then sort by size. Or use the Storage tab’s “Reduce Clutter� feature. For a visual map, a third-party app like DaisyDisk is worth the money if you’re constantly running out of space.
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