What is purgeable space on a Mac?
In Get Info on your startup disk, or the Storage panel, you may see free space plus a “purgeable” amount. Purgeable files are ones macOS has marked as safe to remove automatically when it needs room.
What is in it
- Files that are also stored in iCloud (when Optimize Mac Storage is on)
- Cached data apps have marked as re-creatable
- Some old system and app temporary files
- Time Machine local snapshots, which macOS thins when space gets low
Why it matters
Purgeable space counts toward “available”, so an installer that asks for 30 GB can still run if you have 30 GB available, even if only 10 GB is truly empty. macOS clears purgeable items as the need arises.
Why it sometimes won’t clear
The system only purges when something needs the room, and it does so on its own schedule. If an installer complains about space despite a large purgeable figure, restart and retry first. Removing local snapshots (see this guide) is the usual way to force some of it back.
It is normal for the number to move up and down between checks.
McCleaner scans for free and changes nothing until you pick items to clean.
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Disclosure: this guide is published by the developer of McCleaner. Scanning is free; cleaning is paid, from €1.99. Back up important data before deleting anything. Commands are provided as is.