If you've ever opened Disk Utility, looked at the coloured bar across the top, and wondered what the lighter segment marked "Purgeable" actually is, you're not alone. It's one of the more confusing labels macOS uses, partly because the word "purgeable" doesn't appear anywhere obvious in day-to-day use, and partly because it sits right next to the free space bar without much explanation.
This post explains what purgeable space actually is, why it exists, why it causes Finder and Disk Utility to disagree about your free space, and when (if ever) you should worry about it.
One thing to get out of the way first: purgeable space is about your disk, not your RAM. These are two separate things and two separate problems. RAM (the temporary workspace your Mac uses to hold apps and files that are currently open) is what tools like memory pressure measure. Purgeable space is about your long-term storage: the SSD or hard drive where your files live permanently. If your Mac feels slow, the two are worth understanding separately.
What is purgeable space exactly?
Purgeable space is disk space that is currently occupied by files macOS has decided it can safely remove if it needs room for something else. Think of it as a "soft" kind of storage: the files are there and usable right now, but they come with an invisible label saying "disposable if necessary".
The most common sources of purgeable space are:
- iCloud Drive files cached locally. If you have iCloud Drive enabled, macOS downloads copies of your cloud files to your disk for quick access. These local copies are purgeable because the originals are safely in iCloud. If disk space gets tight, macOS can delete the local copy and restore the cloud-only version, where the file still exists but takes a second longer to open.
- Time Machine local snapshots. When your external backup drive isn't plugged in, Time Machine quietly saves recent backups to your internal disk as "local snapshots". They're purgeable because they're a convenience copy, not the authoritative backup.
- Watched Apple TV downloads. If you've downloaded something to watch offline and you've already watched it, macOS may mark that file purgeable.
- App caches. Many apps write temporary files to disk to speed things up. macOS can clear these if needed.
Apple calls the broader feature Optimised Storage, and you can read more about it in the official Mac Help guide. The short version: macOS tries to use your disk intelligently, keeping useful files close while promising they can go if the disk gets full.
Is purgeable space the same as RAM?
No, and this is worth saying clearly because the two are easy to conflate. Purgeable space lives on your disk. RAM is a completely separate component: the fast, temporary workspace your Mac uses to hold open apps and active data while you're using them. When your Mac's RAM gets stretched, you'll see the effects as slowness and a spinning beach ball. When your disk fills up, you'll see warnings about running out of storage space.
They can both cause problems, but they're different problems with different fixes. If you're seeing the spinning beach ball frequently, read the post on what memory pressure actually means and the guide on how to free up RAM on Mac. Clearing purgeable disk space won't help with RAM at all.
There is one indirect connection worth knowing: when RAM runs very low, macOS writes a "swap file" to your disk to use as overflow storage. That swap file eats into disk space. But the swap file itself isn't purgeable, and freeing purgeable space won't affect RAM either way.
Why does my Mac show different free-space numbers in different places?
This is probably the most common source of confusion around purgeable space. Open Finder, press Cmd+Space, click on your hard drive, and it shows one number for available space. Open Disk Utility and look at the bar graph, and the numbers don't match. Sometimes the gap is several gigabytes.
The reason is that Finder and macOS apps that ask "how much space do I have?" include purgeable space in the available figure. The logic is reasonable: if macOS can free that space automatically, it might as well count as available. You could install a 10 GB app and macOS would quietly evict the equivalent in purgeable files to make room, and you'd never notice.
Disk Utility, on the other hand, shows you the physical picture: this is how the bytes on the drive are actually allocated right now, before any automatic clean-up happens. Purgeable files are real files sitting on the disk, so Disk Utility shows them as "in use" with a separate purgeable colour.
Neither view is wrong. They're answering different questions: Finder says "how much can I effectively use?" and Disk Utility says "what's actually on the drive right now?"
If you want a cleaner picture of your true free space, Disk Utility is more honest. If you want to know whether you can install that big app, Finder's figure (which includes purgeable) is the more practical answer.
How do I remove purgeable space?
The straightforward answer is: you probably don't need to, and macOS will handle it automatically.
When you install a new app, download a large file, or do anything that requires disk space, macOS quietly evicts purgeable files to make room. You won't see a warning or a pause; it just happens. This is the whole point of the system.
If you want to encourage a clean-up without waiting, restarting your Mac is the easiest approach. A restart flushes local Time Machine snapshots and a good portion of app caches, visibly reducing the purgeable figure in Disk Utility. You can also open System Settings, navigate to General then Storage, and use the built-in tools there: options to store files in iCloud, empty the bin automatically, and review large files.
There is no single Terminal command that safely forces all purgeable space to vanish instantly. Third-party apps that claim to do this are generally either triggering the same system call macOS uses automatically, or they're doing something more aggressive that you probably don't want. Treat them with scepticism.
If your Mac is genuinely struggling for space, the more useful step is looking at what's actually taking up the most room. The Storage view in System Settings breaks it down by category and gives you a clearer picture than any purgeable number will.
When should I worry about purgeable space?
Honestly, rarely. Purgeable space is a sign the system is working correctly, not a sign that something is wrong. If your disk has 50 GB of purgeable space, that's macOS doing exactly what it's designed to do: keeping useful files nearby while holding them loosely.
There are a couple of situations where it's worth paying attention:
- Your disk is genuinely getting full. If Disk Utility shows your disk close to capacity even after accounting for purgeable, then you have a real storage problem. Start by looking at the largest non-purgeable files, and consider whether you need them. Purgeable space will be cleared automatically as pressure mounts, but it won't conjure room that isn't there.
- You're getting persistent low-storage warnings. If macOS is warning you about low space and a restart doesn't help, check the Storage breakdown in System Settings. The purgeable column is usually not the culprit; large downloads, duplicated files, and app data usually are. Our guide on why your Mac feels slow covers disk-related slowdowns in more detail.
Outside those situations, the purgeable number is background information. It doesn't need managing.