Why is system data so huge on my macbook?

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Level 1

4 points

Why is system data so huge on my macbook?

Looking at storage in my settings, apparently system data is taking up 169 GB, but when I go to look at my root drive, there's roughly 20 GB in /System, 13 GB in /Library, 11 GB in /usr, 18 GB in /opt, and 8 GB in /private, with all the other files amounting to about 20 MB (with the exception of /Applications which is about 27 GB but I think is under a different category in the storage graph).

Are these files normally this big, and if not, is there a good way of figuring out what's ok to delete?

Also, where's the rest of that 169 GB hiding? That should only amount to ~71 GB, and even including /Applications it should still be less than 100 GB. Anyone know what else might be counted in system data?

Computer specs:

Macbook Air

Apple M1 chip running Sequoia 15.4.1

Thanks, and let me know if any more info would be helpful!

MacBook Air 13″

Posted on Oct 27, 2025 4:09 PM

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Answer 1

Top-ranking reply

HWTech

Level 9

68,078 points

Oct 27, 2025 7:21 PM in response to pebblle

The data is either within your home user folder (or another user's home folder if you have multiple macOS user accounts), or it may be within a hidden APFS backup snapshot. Some data may even be hidden within the hidden Library folder within your home user folder.

You can use OmniDiskSweeper to look for the largest files/folders (won't show the hidden APFS snapshots).

You can also view APFS snapshots using the information in the following Apple article:

View APFS snapshots in Disk Utility on Mac - Apple Support

FYI, when you delete large amounts of data, you may not see any increase in the Free storage space value (only shown within Disk Utility) since that deleted data may still be retained within the hidden APFS snapshots. The APFS backup snapshots will be automatically deleted at some unknown time in the future. For Time Machine backup APFS snapshots, they will generally be automatically deleted in about 24-48 hours after those backups have been completely transferred to external media. Third party backup apps may be different.

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Answer 2

pebblle Author

Level 1

4 points

Oct 29, 2025 12:35 PM in response to HWTech

Thanks for the advice! I downloaded and ran OmniDiskSweeper and turns out I had a couple huge files hidden in Application Support from ages ago when I tried to recover some lost data on my phone (which involved using some programs that I guess backed up my phone partially to do this). Had two files, each 40GB, just sitting there with absolutely no purpose. There's some other bits and pieces I need to clean up to but that was the bulk of it!

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Answer 3

muguy

Level 10

90,908 points

Oct 27, 2025 5:13 PM in response to pebblle

When is the last time that you:

Restarted

Backed up using Time Machine

Emptied your browsing caches

Cleared streaming caches

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