What Is Taking Up Space on My Mac?

Step 1 — Ask macOS itself (30 seconds)

Click the Apple menu → System Settings → General → Storage. The colored bar breaks your disk into Applications, Documents, iOS Backups, Mail, Messages, Photos, System Data and macOS. This answers "which category" — but not "which folder". Two things to know:

• "Documents" is a catch-all: any folder not managed by a system service, including your Downloads, Movies, virtual machines and random disc images.
• "System Data" grows on its own: caches, logs, local Time Machine snapshots. It is the category most likely eating tens of gigabytes you can reclaim — we break it down in Mac System Data, explained.

Step 2 — See the real folder sizes (the missing feature)

Finder does not total up folder sizes by default — which is why "what is taking up space on my Mac" is such a common question. You have three options:

1. Finder, per folder: press ⌘J in a Finder window, enable "Calculate all sizes", then sort by Size. Slow — Finder re-counts every time.
2. Terminal: du -sh ~/* 2>/dev/null | sort -h lists your home folders by size. Fast but text-only.
3. A visual analyzer: a treemap shows every folder as a rectangle sized by disk usage — big blocks jump out instantly. That is exactly what DiskLens does, and unlike desktop apps you don't install anything:

Step 3 — The usual suspects (check these first)

After mapping thousands of disks, the space is almost always in the same ten places. Work down this list against your own map:

1. ~/Library/Developer — Xcode's DerivedData and simulators quietly consume 20–100 GB. Fully regenerable; safe to delete.
2. Old installers in ~/Downloads — every .dmg you ever downloaded and forgot. 5–10 GB is typical.
3. ~/Library/Caches — browser and app caches. Safe to clear; apps rebuild them.
4. node_modules / venv / build folders — if you write code, every project has a regenerable dependency folder several hundred MB deep.
5. ~/Library/Application Support/MobileSync/Backup — old iPhone backups, 4–10 GB each, often for devices you no longer own.
6. Movies & screen recordings — 4K video is ~350 MB per minute. Two holiday clips can outweigh everything else combined.
7. Duplicates — "final_v2.mov", "final_final.mov". Our duplicate finder flags them automatically.
8. VM images & containers — Parallels/UTM disks and Docker data never shrink on their own.
9. Messages attachments — years of photos inside iMessage, counted under "Messages" in Storage Settings.
10. Local Time Machine snapshots — invisible in Finder, 10–50 GB. They expire on their own; tmutil listlocalsnapshots / shows them.

What NOT to delete

Inside the map, big is not the same as deletable. Never remove anything in /System, /Library (system-wide) or ~/Library unless you know exactly what it does — and treat photos, documents, code and archives as "back up first", never "delete". DiskLens color-codes this distinction for every file: red means regenerable junk, blue means back-it-up-before-any-cleanup.

Frequently asked questions

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