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brinkeguthrie

macrumors 6502
Original poster
Jul 22, 2020
285
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Usually at 103gb available. Briefly went up to 115gb. Restarted, back down to 103. Why does it do this?
Screenshot 2025-09-04 at 10.03.37 PM.png
 
System data can fluctuate. Mine right now is 89.56gb on a 1tb Mac mini with 81.48gb free space. I've seen system data take up over 100 gb at times.

This is what is in system data to better understand how it works:
AFPS snapshots from Time Machine
Temporary files
System and crash logs
Caches
Also, emails and attachments can fall in this category too since they are in hidden Library folders.
 
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Add to that list, virtual memory paging files which can get quite large if you have a lot of stuff running. Seeing as you have 256 GB of storage, I'm going to take a guess you might have 8 GB of RAM on a base model Air. If this is true, you could easily generate big VM files the system uses to temporarily park stuff you have open that doesn't fit into RAM.

If you want to see the VM, you can use the Go to Folder command in the Finder and paste in /System/Volumes/VM. But do NOT mess with the files or you'll crash your machine immediately. They will get deleted automatically when you restart. I've got about 8 GB worth of VM files sitting there as we speak.
 
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