How to Fix “System Data” Taking Up 100GB+ on Mac: The Ultimate Cleanup Guide

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It is the most annoying notification in the Apple ecosystem: “Disk Full.”

You go to System Settings > General > Storage to see what is taking up space. You expect to see your Videos or Photos. Instead, you see a grey bar labeled “System Data” (formerly called “Other”) occupying 150GB, 200GB, or even more.

What is System Data? In macOS Sequoia (15.x), System Data is a “junk drawer.” It contains:

• Time Machine local snapshots (the #1 culprit).
• Adobe/FCPX render caches.
• Log files.
• Browser caches.
• Old iPhone backups.

Recently, users on macOS 15.3 have reported a caching bug where this data balloons out of control. If your System Data is over 50GB, something is wrong. Here is how to fix it and reclaim your drive.

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Method 1: The “Ghost” Killer (Time Machine Snapshots)

Risk: Low

This is the most common cause. When Time Machine prepares to back up but isn’t connected to your external drive, it saves “Local Snapshots” on your Mac’s SSD. Sometimes, macOS forgets to delete them.

How to Fix it:

1. Open Terminal (Cmd + Space, type “Terminal“).

2. Type this command to see the list of snapshots:

tmutil listlocalsnapshots /

If you see a long list of dates (e.g., com.apple.TimeMachine.2026-02-01...), this is your problem.

3. To delete them all instantly, type this command:

for d in $(tmutil listlocalsnapshots / | grep -oE '[0-9]+-[0-9]+-[0-9]+-[0-9]+'); do sudo tmutil deletelocalsnapshots $d; done

(You will need to enter your admin password).

4. Wait. It may take a few seconds. Once the terminal returns to the prompt, check your Storage settings. You might have just freed up 50GB+.

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Method 2: The Cache Flush (Manual Cleanup)

Risk: Medium (Follow steps carefully)

Apps store temporary files to run faster. Over time, these files become corrupt or obsolete.

How to Fix it:

1. Open Finder.
2. In the menu bar, click Go > Go to Folder.
3. Type: ~/Library/Caches and hit Enter.
4. Sort by Size: Go to View > Show View Options > Check “Calculate all sizes.”
5. Look for the Giants:
   • com.adobe... (Adobe apps can hoard 20GB+).
   • com.apple.helpd (A known bug in macOS help documentation).
   • com.spotify.client (Spotify caches offline songs).
6. Action: You can safely delete the contents of these folders (drag to Trash). Do not delete the folder itself, just the files inside.
7. Empty Trash and Restart.

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Method 3: The Developer Trap (Xcode & Simulators)

Success Rate: High (For Devs) Risk: Low

If you are a developer using Xcode, this is almost certainly your issue. Xcode saves every device simulation and build index forever.

How to Fix it:

1. Derived Data:
   • Go to ~/Library/Developer/Xcode/DerivedData.
   • Delete everything in this folder. It is safe; Xcode will just rebuild what it needs next time.
2. iOS Device Support:
   • Go to ~/Library/Developer/Xcode/iOS DeviceSupport.
   • This folder contains symbols for every iPhone you have ever plugged in. If you see folders for iOS 14, 15, or 16, delete them. You only need the version you are currently testing.

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Method 4: The Hidden Logs

Success Rate: Low Risk: Low

Sometimes a crashing app writes an error log every second, creating massive text files.

1. Go to ~/Library/Logs.
2. Check for huge files. If you see a log file that is 5GB or 10GB, delete it immediately. It means an app is misbehaving.

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Summary Checklist

If “System Data” is still huge after doing all of the above:

1. Check the “Bin”: Yes, sometimes the Trash itself counts as System Data until emptied.
2. Old iOS Backups: Connect your iPhone, open Finder, click “Manage Backups,” and delete backups from 2024 or 2025.
3. Indexing Bug: Sometimes the storage report is wrong. Force Spotlight to re-index your drive:
   • Terminal Command: sudo mdutil -E /

Did this guide help you reclaim your space? Share your “Before vs. After” screenshot in the comments!