Finding specific things

Hidden storage use

Updated 2026-07-31 · 4 min read

The gap between what Finder reports and what Storage settings claims is real, and it has four usual causes.

Purgeable space

macOS counts space it *could* free — local snapshots, cached iCloud files, deletable caches — as available. Finder shows optimistic free space that a large copy operation may not be able to use immediately.

diskutil info / | grep -i "free\|available"

The two numbers there differ, and the difference is purgeable.

Local Time Machine snapshots

Hourly, kept on the internal disk, thinned automatically:

tmutil listlocalsnapshots /

These are the most common cause of unexplained tens of gigabytes.

System Data

A catch-all in Storage settings covering caches, logs, snapshots and anything unclassified. Its size is often alarming and rarely actionable directly. The honest way to find out what it is:

sudo du -h -d 2 /System/Volumes/Data 2>/dev/null | sort -hr | head -30

Files inside packages

A Photos library is one item to Finder and 200 GB on disk. Same for Logic projects and iOS backups in ~/Library/Application Support/MobileSync.

The audit that actually works

du -h -d 2 ~ 2>/dev/null | sort -hr | head -25

Then repeat one level deeper into whatever dominates. Ten minutes of this beats any cleaning app, because you end up understanding your own disk.

Why Spotlight cannot answer this

The largest offenders are usually inside ~/Library or inside packages — both excluded. A search for "everything over 1 GB" through Spotlight misses the exact files causing the problem, which is why the Terminal remains the reliable tool here unless your index covers those places.

Common questions

What is purgeable space on a Mac?

Space macOS can reclaim on demand — snapshots and caches. It is counted as free but is not always immediately usable.

Can I delete local snapshots?

tmutil deletelocalsnapshots <date> removes one. macOS also thins them automatically under pressure.