In short
- Available space includes purgeable space — caches and snapshots macOS deletes on its own when it needs room. MoreRoom shows it separately, as Finder does not.
- MoreRoom measures what files really take on disk. Shared copies (APFS clones) and compressed files take less than their logical size; Finder adds full sizes.
- Like Finder, MoreRoom uses decimal units (1 GB = 1,000,000,000 bytes). Terminal and some apps use binary units (GiB), which look about 7% smaller.
Free space: three different answers
| Where | What it calls free |
|---|---|
| Finder, System Settings › General › Storage, MoreRoom’s home screen and header (“available”) | Free space plus purgeable space |
Terminal’s df, MoreRoom’s Locations list in the sidebar |
Free space only |
| MoreRoom’s header, next to “available” | “size purgeable”, when there’s more than 100 MB |
Purgeable space is space macOS promises to give back on its own when it needs room: caches, local Time Machine snapshots, iCloud files it can download again. It counts as available because you can use it — but it isn’t empty yet. Our guide Purgeable space on a Mac explains it in detail.
Size of a folder
MoreRoom shows the space a file really takes on disk. Finder’s Get Info shows two numbers, and other tools may add sizes differently:
- APFS clones — for example copies made with Finder’s Duplicate — share their data. MoreRoom counts shared space once; Finder counts each copy in full. The inspector says APFS clone — Shares space with a copy. Free Without Deleting turns identical files into such clones.
- Compressed files — including cold files compressed by Free Without Deleting — take less than their Logical size, which the inspector also shows.
- iCloud files only in the cloud take almost nothing on your Mac (“Only in the cloud”), even if Finder shows their full size.
- Hard links are counted once.
The scan total is smaller than the space used
- Without Full Disk Access, protected folders are skipped. See Grant Full Disk Access.
- Some folders need admin access (system caches, other users), and local snapshots and file system metadata aren’t files you can see. Scan your Mac, then open System Data, explained: it shows this hidden part as Not visible without admin access.
- macOS’s own volumes (sealed system, Preboot, Recovery, virtual memory) are outside your data.
- Folders in Settings › Exclusions are not scanned.
GB or GiB?
MoreRoom, like Finder and System Settings, uses decimal units: 1 GB = 1,000,000,000 bytes. Terminal tools such as du -h and some apps use binary units (GiB, sometimes written “G” or even “GB”): 1 GiB = 1,073,741,824 bytes. The same folder looks about 7% smaller in GiB. Try our GB vs GiB converter.
Numbers that change after a cleanup
Items moved to the Trash still take space until you empty it, and an app may keep deleted files open. See Space didn’t come back.