APFS Filesystem Internals · Purgeable Space Explained

How to Find & Delete Hidden APFS Local Snapshots on macOS (tmutil Guide)

Direct Answer Summary (TL;DR)

If you just deleted 50 GB of files and emptied the Trash—yet Disk Utility, Xcode, or Docker still says your disk is full—your storage blocks are pinned by APFS Copy-on-Write local snapshots. Because APFS snapshots record a point-in-time reference to every block on the volume, deleting a file only removes its directory entry until the snapshot itself expires. You can inspect and release those pinned blocks immediately with tmutil listlocalsnapshots / and tmutil thinlocalsnapshots / 25000000000 4, or inspect them visually in StorageSage's System Data & Volume Engine.

Why Finder, Disk Utility, and df -h All Show Different Free Space

Apple File System (APFS) maintains two distinct free-space metrics on every volume container:

volumeAvailableCapacityForImportantUsageKey

Finder “Available (Purgeable)” Space

Includes physical free blocks plus blocks currently held by APFS local snapshots and iCloud evictable caches that macOS promises to release under high-priority write pressure.

f_bavail * f_bsize (statfs)

True Unallocated Kernel Blocks

What POSIX tools (df -h, Docker, Postgres, and git clone) actually see. If APFS snapshots hold 60 GB of deleted blocks, CLI tools will fail with ENOSPC: No space left on device.

3 Commands to Audit & Purge APFS Local Snapshots

1. List all local snapshots on your boot volume

tmutil listlocalsnapshots /
# Example output:
# com.apple.TimeMachine.2026-04-15-184210.local
# com.apple.TimeMachine.2026-04-16-011504.local
# com.apple.os.update-MSUPrepareUpdate

2. Delete a specific APFS local snapshot by timestamp

tmutil deletelocalsnapshots 2026-04-15-184210

3. Thin all purgeable snapshots automatically (e.g., reclaim 25 GB at urgency 4)

tmutil thinlocalsnapshots / 25000000000 4

Inspect APFS Volumes & Snapshots Instantly in StorageSage

StorageSage's SystemDataEngine uses a lock-free Howard Hinnant civil-calendar timestamp parser to enumerate APFS local snapshots in 0.18 seconds alongside real-time physical vs. purgeable volume telemetry.

Download StorageSage Free (.dmg)brew install --cask storagesage

Related macOS Storage Engineering Guides