How to Clear Hidden "System Data" on macOS Sequoia & Sonoma

In macOS Sequoia and Sonoma, Apple groups any file that is not a standard document, application, music, or video file into the catch-all category known as System Data (previously called "Other" storage in older macOS versions).

Because macOS does not let you click on "System Data" to see individual files in System Settings, users are left wondering which applications or background daemons are hogging their drive.

1. What Actually Makes Up "System Data"?

Contrary to popular belief, System Data is rarely actual macOS core operating system files. The base macOS system is sealed in a read-only Signed System Volume (SSV) taking only ~25–35 GB.

When System Data explodes past 60 GB, the space is almost always occupied by five specific components:

1. Time Machine APFS Local Snapshots (invisible backup deltas saved on your internal drive).
2. App Caches & Application Support in ~/Library/Caches and ~/Library/Application Support.
3. Sandboxed Group Containers in ~/Library/Group Containers.
4. Old iOS / iPadOS Local Backups in MobileSync/Backup.
5. macOS Sleepimage & Swap Files in /private/var/vm.

2. Culprit #1: Purge APFS Time Machine Local Snapshots

If you use Time Machine, macOS creates local APFS snapshots on your primary drive whenever your external backup disk is unplugged. While macOS is supposed to clean them automatically when space is tight, this mechanism frequently fails, leaving dozens of gigabytes stranded.

Check for active local snapshots using Terminal:

tmutil listlocalsnapshots /

To delete a specific local snapshot date:

sudo tmutil deletelocalsnapshots 2026-08-15-143022

To purge all local snapshots in one command:

for d in $(tmutil listlocalsnapshotdates / | grep "-"); do sudo tmutil deletelocalsnapshots $d; done

3. Culprit #2: Application Support & Orphaned Containers

When you uninstall an app by dragging it to Trash, its data in ~/Library/Application Support and ~/Library/Containers stays on your drive forever. Apps like Spotify, Steam, Adobe Creative Cloud, Slack, and Discord frequently leave 10–40 GB of cached media, electron logs, and update archives behind.

Open your User Library folder in Finder:

open ~/Library/Application\ Support

Look for folders belonging to apps you haven't used in months or already uninstalled.

4. Culprit #3: Stale iOS & iPadOS Backups

If you have ever connected your iPhone or iPad to your Mac to perform a local backup via Finder, each full backup can take 50–120 GB of uncompressed data.

You can check the local backup storage folder here:

~/Library/Application Support/MobileSync/Backup

You can manage and delete old device backups either via System Settings → General → Storage → iOS Files or by revealing the folder in Finder and deleting obsolete device folders.

5. Culprit #4: User Caches & Diagnostic Logs

Web browsers, video editors, audio DAWs (Logic Pro, Ableton), and system frameworks generate gigabytes of cache in:

~/Library/Caches

You can safely delete contents inside non-essential app cache folders:

rm -rf ~/Library/Caches/Google/Chrome/*
rm -rf ~/Library/Caches/com.spotify.client/*
rm -rf ~/Library/Logs/DiagnosticReports/*

System Data Cleanup Summary Checklist

Keep System Data Lean with DiskAtlas

DiskAtlas is built specifically with macOS APFS awareness and a SafeScore engine to spot bloated System Data components instantly without risking your system integrity or deleting important files.