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The New Math: How Sierra Calculates Free Space

Over at Six Colors, Jason Snell reveals that macOS 10.12 Sierra calculates free space on your drive differently than in the past. Along with drive space that doesn’t contain any data, Sierra now includes in the calculation “purgeable space,” which holds data that can be deleted from your drive because Sierra can redownload it if necessary. This purgeable data includes stuff like files stored in iCloud, certain large fonts, and unused dictionaries, along with purchased video content from the iTunes Store and photos and videos you have in iCloud Photo Library (those last two require you to have enabled the appropriate settings in iTunes and Photos). Keep this in mind, or you could get confused when trying to determine how much space you have left on your drive!favicon follow link

 

Comments about The New Math: How Sierra Calculates Free Space
(Comments are closed.)

In Sierra, is there a simple way to check how much is truly free space, i.e. free space reported as it used to be?
Adam Engst  An apple icon for a TidBITS Staffer 2016-10-10 15:16
Yes, in the Get Info window for the drive, the purgeable number is broken out separately.
OK. But no way to get it to display like that in the Status Bar?
Adam Engst  An apple icon for a TidBITS Staffer 2016-10-10 15:38
Not in the status bar, but asking Siri how much free space you have provides the true number, as does looking in System Information.
OK. Thanks, Adam.
Mark Chaffin  2016-10-10 14:44
How about if all options to store data in iCloud are disabled (including photos, movies, etc)? Does Sierra then calculate actual disk usage?
Adam Engst  An apple icon for a TidBITS Staffer 2016-10-10 15:22
I'm not 100% certain, but in some quick tests, the purgeable number in Get Info didn't change when I toggled those checkboxes back and forth.

Sierra isn't super quick about updating some of these numbers, so I can't say that these tests are definitive (and my Sierra Mac isn't a great test machine in this case, since I don't have any iTunes content, or that much in the Desktop and Documents folders).
Chris Kohuch  2016-10-11 01:40
I'm not sure if this is a definitive answer, but I don't have any of the iCloud storage options turned on and my Get Info never shows any purgable space.
In El Capitan and earlier, a Get Info window for a volume shows "Available" and "Used", which when added together equals "Capacity".

In Sierra, is "Available" plus "Used" now greater than "Capacity"?
Adam Engst  An apple icon for a TidBITS Staffer 2016-10-10 15:17
No, but Available now includes purgeable data. So the Available line will look larger in Sierra than El Capitan.
And "Used" does NOT include purgeable data?
Adam Engst  An apple icon for a TidBITS Staffer 2016-10-11 10:28
Here's what my MacBook Air says, roughly:

Capacity: 250 GB
Available: 79 GB (50 GB purgeable)
Used: 171 GB

And looking in System Information reveals that 29 GB is truly available free space.

So I guess that means that purgeable data is being "removed" from "Used" in the Get Info window.
Interesting.

So truly free = available - purgeable