macOS System Storage Is High? Complete Guide to Fix “System Data” Taking Up Space

If you’ve checked Mac storage and noticed that System Data (or “System Storage”) is consuming an unusually large amount of disk space, you are not alone. This is one of the most common and confusing macOS issues, especially for users with limited SSD capacity.

This in-depth guide explains what macOS System Data really is, why it grows uncontrollably, and how to safely reduce it without damaging your system. The article is written for everyday users and power users alike, with practical steps and expert-level tips.

What Is System Data on macOS?

System Data (formerly called “Other”) is a storage category used by macOS to group files that don’t clearly fit into apps, documents, photos, or media.

It typically includes:

System caches and temporary files
Log files
App support data
Virtual memory and swap files
macOS updates and installer leftovers
iOS device backups
Browser caches and extensions
Developer tools and simulators

Because many of these files are hidden or dynamically managed, macOS does not always clean them up efficiently.

Why Is macOS System Storage So High?

There is no single cause. System Data grows due to a combination of normal macOS behavior and long-term usage patterns.

Common Reasons System Data Becomes Huge

1. Cached Files Accumulate Over Time

macOS and apps store cache files to improve performance. Over months or years, these files can grow into multiple gigabytes.

2. Old iOS Backups

If you’ve backed up an iPhone or iPad to your Mac, old backups may still exist—even if you no longer use the device.

3. macOS Update Residue

Failed updates, partial downloads, or installer files may remain on disk after system upgrades.

4. Virtual Memory and Swap Files

When RAM is under pressure, macOS creates swap files that can become very large, especially on Macs with limited memory.

5. Developer Tools (Xcode)

Xcode simulators, device support files, and archives can consume tens of gigabytes.

6. Time Machine Local Snapshots

macOS creates local backups when your Time Machine drive is disconnected. These snapshots are hidden but count toward System Data.

How to Check What’s Using System Data

Before deleting anything, it’s important to identify what’s consuming space.

Check Storage Breakdown

Go to Apple menu → System Settings → General → Storage
Review the “System Data” size
Click Recommendations for automated suggestions

Use Finder to Reveal Hidden Files

Open Finder
Press Command + Shift + G
Navigate to: ~/Library

This folder contains caches, logs, and application support files.

How to Reduce macOS System Data Safely

1. Restart Your Mac (Simple but Effective)

Restarting clears:

Temporary system files
Some swap and cache files

This alone can reduce System Data noticeably.

2. Delete Cache Files Manually

User Cache

Finder → Go → Go to Folder
Enter: ~/Library/Caches
Delete folder contents (not the folder itself)

System Cache (Optional)

/Library/Caches

Administrator access required.

macOS will recreate needed cache files automatically.

3. Remove Old iOS Backups

Open Finder
Select your Mac → Manage Backups
Delete outdated device backups

This can instantly free several gigabytes.

4. Clear Time Machine Local Snapshots

To check snapshots:

tmutil listlocalsnapshots /

To remove them:

sudo tmutil deletelocalsnapshots [snapshot-date]

Once your external Time Machine drive reconnects, macOS usually removes these automatically.

5. Delete macOS Update Files

Check:

/Library/Updates

If updates are stuck or incomplete, safely delete the contents of this folder.

6. Clean Up Xcode and Developer Files

If you use Xcode:

Delete unused simulators
Remove old device support files
Clear derived data: ~/Library/Developer/Xcode/DerivedData

This is one of the biggest System Data offenders.

7. Review Large Hidden Files

Sort folders by size using Finder’s List View and identify unusually large files.

Common locations:

~/Library/Application Support
~/Library/Containers
/private/var

Proceed carefully—delete only what you recognize.

Should You Use Mac Cleaning Apps?

macOS can be cleaned manually, but reputable third-party tools can help visualize storage usage.

Pros:

Easier identification of large files
Safer cleanup for non-technical users

Cons:

Over-aggressive cleaning may remove useful data
Avoid unknown or “one-click” cleaner apps

Always verify what will be deleted before proceeding.

How to Prevent System Data From Growing Again

Restart your Mac periodically
Keep at least 15–20% disk space free
Avoid excessive background apps
Review storage after major macOS updates
Connect your Time Machine drive regularly
Remove unused developer tools

FAQs About macOS System Data

Is it safe to delete System Data?

You cannot delete System Data directly, but removing cache files, backups, and snapshots is safe when done correctly.

Why does System Data increase after an update?

macOS downloads installer files, creates backups, and stores logs during updates. Cleanup often happens later or manually.

Will upgrading macOS fix high System Data?

Sometimes, but not always. A clean install is the most effective solution if the issue persists.

How much System Data is normal?

It varies by usage, but 15–40 GB is common. Anything significantly higher usually warrants cleanup.

Conclusion: Take Control of macOS System Storage

High System Data usage is not a bug—it’s a side effect of how macOS manages performance, safety, and backups. With the right approach, you can reclaim dozens of gigabytes without risking system stability.

By understanding what System Data contains and applying targeted cleanup methods, your Mac will run faster, smoother, and with far more available storage.