Storage

Mac storage is full — here's how to free up space (and what “System Data” actually is)

By the Noah team·Updated June 13, 2026·11 min read
Short answerA full Mac disk is usually a mix of forgotten large files, old caches and logs, local Time Machine snapshots, and iOS or app data — lumped together under the vague “System Data” (formerly “Other”) category. Open > System Settings > General > Storage to see the breakdown, then work top-down: empty the Trash, clear local snapshots, delete large unused files, and offload what you can to iCloud. “System Data” is mostly caches, logs, and snapshots — it shrinks on its own once you clear the real culprits below.

You go to save a file or update macOS and get “Your disk is almost full” — but when you look, your own files don't seem big enough to explain it. The space is real; it's just hidden in places the Finder doesn't show you by default: caches, snapshots, app data, and the catch-all macOS labels “System Data” or “Other.”

This guide shows you exactly where the space went and how to get it back safely — without deleting something you'll regret. You can do all of it by hand. (Or let Noah find the safe-to-remove gigabytes for you and clear them on your approval — more at the end.)

First: see what's actually using the space

Don't start deleting blindly. Open > System Settings > General > Storage. The bar at the top breaks your disk into categories — Applications, Documents, Photos, macOS, and the vague System Data. Click the little ⓘ next to Documents and Applications to see your largest files and apps, sorted by size.

For a precise, no-nonsense view from Terminal, this lists the biggest folders in your home directory:

du -sh ~/* ~/Library/* 2>/dev/null | sort -rh | head -20
Sorts your top-level folders biggest-first. The 2>/dev/null hides permission warnings.

What “System Data” really is (and how to shrink it)

“System Data” (called “Other” on older macOS) is the category everyone panics about. It's not one thing — it's everything macOS doesn't sort elsewhere: caches, logs, local Time Machine snapshots, app support files, fonts, plugins, and temporary files. On a healthy Mac it's often 10–40GB. When it balloons to 100GB+, one of the things below is the cause.

You can't (and shouldn't) delete “System Data” directly — there's no single folder. Instead you shrink it by clearing the specific culprits: snapshots, caches, and old backups. Do those and the number drops on its own.

1. Local Time Machine snapshots (the usual hidden hog)

Symptom: “System Data” is huge and you have Time Machine on. Why: even when your backup drive is unplugged, macOS keeps local snapshots on your internal disk. They're meant to be temporary, but can quietly hold tens of gigabytes.

Check for local snapshots:

tmutil listlocalsnapshots /
Each line is a snapshot taking up space on your internal disk.

Fix: macOS thins these automatically when space runs low, but you can force it. This thins local snapshots, keeping at least 4 most-recent, freeing the rest:

sudo tmutil thinlocalsnapshots / 999999999999 4
Frees the space held by older local snapshots immediately.

2. Trash, Downloads, and big forgotten files

The easy wins. The Trash still counts against your disk until emptied — right-click the Trash icon > Empty. The Downloads folder is where installers (.dmg), large attachments, and one-off files pile up; sort it by size and clear what you don't need. Then hunt large files anywhere with:

find ~ -type f -size +1G 2>/dev/null
Lists files larger than 1GB in your home folder. Review before deleting.

3. Caches and logs

Symptom: steady “System Data” growth over months. Why: apps and the system write caches and logs that aren't always cleaned up. Fix: most live in ~/Library/Caches. It's generally safe to clear app caches (apps rebuild them), but quit the apps first, and never delete the Library folder itself. See what's there:

du -sh ~/Library/Caches/* 2>/dev/null | sort -rh | head -15

4. App data: iOS backups, Xcode, GarageBand, Photos

A few apps are notorious space hogs. iPhone/iPad backups stored on your Mac can be many gigabytes (manage them in the Finder sidebar > your device > Manage Backups). Xcode hides huge caches in ~/Library/Developer/Xcode/DerivedData and old simulators. GarageBand and Logic bundle gigabytes of sound libraries you may never use. And the Photos library — especially with duplicates and videos — is often the single largest item on a personal Mac.

5. Offload to iCloud (without losing anything)

Fix: in > System Settings > General > Storage, turn on “Store in iCloud”. Files you rarely open are kept in the cloud and downloaded on demand, freeing local space while keeping everything available. Optimize Mac Storage for Photos does the same for your library. This is the safest way to reclaim space — nothing is deleted, just offloaded.

The fastest path, in order

  1. Open Storage settings and note the breakdown.
  2. Empty the Trash and clear Downloads.
  3. Thin local Time Machine snapshots.
  4. Delete large unused files, old iOS backups, and dev caches.
  5. Turn on Store in iCloud / Optimize Storage, then restart.

That sequence reclaims space on almost any Mac — and watch “System Data” shrink as you go.

Or let Noah find the safe gigabytes

Hunting through caches, snapshots, and hidden folders is exactly the tedious part. Noah scans your Mac, identifies what's genuinely safe to remove — purgeable caches, stale snapshots, orphaned backups — shows you the exact list before it touches anything, and clears it on your approval.

Just say “my Mac is out of space,” and Noah does the digging for you.

Try Noah free →

Frequently asked questions

What is “System Data” on my Mac?

“System Data” (formerly “Other”) is everything macOS doesn't sort into a named category: caches, logs, local Time Machine snapshots, app support files, fonts, and temporary files. It's normal for it to be 10–40GB. When it's much larger, the cause is usually local snapshots or large app caches.

Is it safe to delete System Data?

You can't delete it directly — there's no single folder. Instead you shrink it safely by clearing its components: thin local Time Machine snapshots, empty the Trash, and clear app caches (with the apps quit). Avoid deleting anything in /System or the Library folder itself.

How much free space should a Mac have?

Keep at least 10–15% of your disk free. Below about 10%, macOS slows down noticeably and may refuse to install updates, because it needs free space for virtual memory and temporary files.

Why is my Mac storage full when I deleted files?

Two common reasons: the files are still in the Trash (which counts until emptied), and local Time Machine snapshots may still reference the data. Empty the Trash and thin local snapshots, and the space should return.

Can I just use a cleaner app?

You can, but be careful — many aggressively delete caches apps need, or charge for things macOS does for free. The built-in Storage tools plus the steps above handle most cases. Noah takes a safer approach: it shows you exactly what it'll remove and removes nothing without your approval.

Keep readingWhy is my Mac so slow? 10 causes and fixes →MacBook running hot & fans loud — how to fix it →

Commands in this guide are standard, read-only macOS diagnostics unless noted; anything that changes your system is called out. When in doubt, back up first with Time Machine.