macOS hides thousands of system and app files by default. When caches or logs grow out of control, that hidden layer is usually where the missing gigabytes have gone.
Short answer: press Command + Shift + . in Finder to reveal hidden files, then open the User Library to find the heaviest caches and leftover app data.
Revealing hidden files
The fastest path is the built-in Finder shortcut:
- open Finder
- go to your Home folder or Macintosh HD
- press Command + Shift + .
Hidden files and folders appear as faded items. Press the same shortcut again to hide them.
From there, switch Finder to List view and sort by the Size column to find the heaviest items.
The User Library
Most hidden bloat on a Mac lives inside your User Library, not the system library.
- open Finder
- click Go in the menu bar
- hold Option, and click the Library item that appears
The two folders that matter most:
- ~/Library/Caches — temporary files an app can rebuild. Safe to empty the contents, but do not delete the Caches folder itself.
- ~/Library/Application Support — per-app data. If an app is uninstalled but a large folder still sits here, that folder is usually safe to remove.
Avoid deleting random items you do not recognize. Library contents are real app state — guess wrong and the app may fail to launch.
When the culprit is not in Library
If Library is small but your Mac still shows huge "System Data" usage, the source is usually local Time Machine snapshots or purgeable iCloud caches, not Library files.
Better next routes
If "System Data" or "Other" is the real pressure, continue with What Is Purgeable Storage on Mac?.
If local Time Machine snapshots are filling the drive, use How to Delete Old Time Machine Backups From Mac Hard Drive.