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I just got an M1 MacBook Air base model with a 256GB SSD. After setting it up to my liking and running Migration Assistant and getting rid of junk I don't need, I wondered how much free space I had on the SSD.

  • Stats menu bar items says 82% is used leaving 18% free or about 46GB free.
  • Finder says 121.87 GB available.
  • Disk Utility says 43.75 GB Free.
  • System Settings > General > Storage says 122.7 GB.
  • command line tool df also says 18% (46GB) available

I understand that they all might be looking at different things, so this is confusing to just about any person.

enter image description here

Which one is closest to being accurate?

[edit] Here are the results from Mints, mentioned in the answer:

Volume <Macintosh HD>:
    format APFS (NOT case sensitive)
    free space on </Volumes/Macintosh HD> is 42.65 GB of total 245.11 GB
    used space 202.45 GB
    available for important usage 159.98 GB
    available for opportunistic usage 30.3 GB
    sparse file storage available
    file cloning available
    volume supports compression.
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  • 46 versus 43.75 GB is probably metric versus imperial gigabytes. I don't know about the others.
    – Mark
    Commented Apr 13, 2023 at 22:54
  • 2
    Is "metric vs. imperial" a joke? I don't think either the metric or imperial measuring systems take stances on kB/KiB
    – rydwolf
    Commented Apr 14, 2023 at 1:00

1 Answer 1

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Calculation of free space on APFS is apparently not so easy (see https://eclecticlight.co/2023/04/12/when-the-finders-error-exceeds-50/ for details).

Over those years, the Finder has repeatedly shown errors in accounting for used and free space on APFS, although they’re seldom as large as this.

Several of the valuable new features in APFS, like snapshots, sparse files and clones, make it difficult to arrive at a precise estimate of free space. However you do that, the figure is dynamic and has to make some assumptions. Although I don’t know how the Finder or Disk Utility make their estimates, Mints uses a proven part of the API through URLResourceValues that’s readily accessible and correlates well with Disk Utility.

The results from DiskUtility or df are most likely more accurate than Finder.

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  • This afternoon Stats reports that the SSD is only 39% full. Quite a change from yesterday's 82%. Have I deleted anything? No.
    – Buadhai
    Commented Apr 14, 2023 at 7:50
  • @Buadhai Stats may do even worse than Finder in handling APFS data structures.
    – nohillside ♦
    Commented Apr 14, 2023 at 8:58

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