Purgeable space on Mac: why "available" is not free

Finder reports "available" as free space plus purgeable space. Purgeable space is data macOS may delete on its own when it needs room, such as local snapshots and caches. An app asking the file system sees only the truly free part. Broza shows both numbers on separate lines and never adds purgeable to free.

Why Finder shows more available space

Finder adds purgeable space to free space. Broza shows them separately because purgeable space is not guaranteed to be available to your apps right now.

Where purgeable space comes from

They are what "enter Time Machine" browses when the backup disk is not attached, and what lets a failed update roll back. They are also why a Mac reports gigabytes of "purgeable" space: macOS deletes snapshots itself when the disk fills.

Free space belongs to the container

A Mac's SSD holds one APFS container with several volumes (System, Data, Preboot, Recovery, VM). Free space belongs to the container, not to any single volume. That is why a "percentage full" per volume is misleading, and why Broza reasons at the container level.

What the honest numbers look like

Physical disk  disk0  —  APPLE SSD AP1024Z  (1.00 TB)
└─ APFS container  disk3  (994.7 GB)
   ├─ Used        812.4 GB  ████████████████░░░░  81.7%
   ├─ Free         98.1 GB
   └─ Purgeable    84.1 GB  ← estimate; macOS shows this as "available"

broza scan prints used, free and purgeable on separate lines, and never adds purgeable to free.

Check it on your Mac

Broza is a free, open-source command-line tool. Every command below is read-only except clean, and clean is a dry run until you add --apply.

$ broza scan

Not installed yet? Install Broza with Homebrew, the installer script, or Cargo.