Can’t clear macOS purgeable space? This app can help you do it!
Here I was trying to install some games using CodeWeavers CrossOver, but the game’s installer was reporting that I have only 32GB of space left. Weird, macOS is telling me that I do have about 112GB of available space. What’s happening? As it turns out, depending how files are deleted, macOS may not necessarily delete it from the file system, but keeps it as purgeable space. So in order to regain the actual free space, you will need to clear macOS purgeable space. But you will also quickly notice that macOS doesn’t give you any way to do that!
As you can see in the screenshot above, macOS’ System Information shows that I have 121 GB of available space. However, when I “Get Info” on the Macintosh HD using Finder, I can see that the 121 GB of available space actually includes 88.79 GB of purgeable space. Which means 121 – 88.79 = 32.21 GB of free space!
And so, this is where an app like DaisyDisk comes in to the rescue!
Clear macOS purgeable space with DaisyDisk
DaisyDisk is a pretty cool app that provides visualisation of your disk. The chart generated by DaisyDisk will shows you where all the space are being used. Here, you can see that the free space is reported as 32.2 GB, and there’s 98.7 GB of hidden space! And part of that is where the purgeable space lies.
To find the purgeable space, you will need to look at the details of the dark purple or whichever colour DaisyDisk uses to represent hidden space. The video below will show you how you can look for it. Once you find where it is, drag and drop it to the collector at the bottom left part of the app and then click delete to clear it. You will just need to wait for the process to complete. I’ve cut out some of the wait time in the animated GIF below, but it took roughly 2+ minutes to clear out 88 GB if purgeable space on my Mac.
Once cleared, you will initially see that macOS will report more available space. Which is technically wrong, since you have manually deleted the purgeable space. So while the free space has increased, macOS somehow still isn’t aware that the purgeable space has already been deleted. But once you manually start a Time Machine backup, macOS will then report it correctly.
Can I delete this myself without paying for an app?
Well, yes. But it’s not that simple. You would usually not face this problem as macOS generally does a pretty good job clearing up the purgeable space when you need the space. And in order to clear the purgeable space, you need to know where macOS “hides” them. DaisyDisk blogged on this topic here which I would recommend you to read too. While DaisyDisk does not necessarily share in detail what it looks out for since that’s their IP, the blog post does reveal that there’s quite a number of places where it would seek out files that are safe to clear, such as temporary files, caches, etc.
So perhaps its a life-hack to just rely on apps like DaisyDisk to do the job for you with a single click. If you just want to do this once, you could perhaps download and get a trial license to clear it for you as well.
But what it I *really* don’t want to spend any money at all?
You could run a time machine backup and see if macOS would clear up the purgeable space. Most of the time, the purgeable space is made up of local time machine snapshots. So if you do not regularly back up your Mac, the snapshots tend to accumulate and it can be quite sizeable after a while. I also suspect that any recent deletes will just be “kept” as snapshots of your disk. So when I recently deleted 50-60 GB of space and since I still have about 30+GB of space left, macOS will decide to “keep” it temporarily until I back it up with Time Machine. But this becomes a problem for me since I need about 36 GB of free disk space to install a game.
In this case, I could wait for Time Machine to complete its backup and clear up the purgeable space, but that will take a couple of hours to complete. But then again, if time is more important to you, spending $9.99 is probably less than 2 cups of coffee you would spend in the week.
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