Mac storage full? What actually takes up space on a developer's Mac

Updated 15 October 2026

When a developer's Mac says the disk is almost full, the space is usually in a handful of folders that build tools fill and never empty. Here is how to find them, what is safe to clear and what to leave alone.

Step 1: get the real numbers

Open System Settings › General › Storage for macOS's breakdown. In Terminal:

df -h /System/Volumes/Data

On current macOS your files live on the Data volume, so df -h / shows only the small, read-only system volume as used. The available space is the same for both.

Step 2: find the biggest folders

du -hd 1 ~ 2>/dev/null | sort -hr | head -20
du -hd 1 ~/Library 2>/dev/null | sort -hr | head -15

Repeat inside whichever folder is biggest until you find the culprit. These can take a few minutes on a full disk.

macOS protects some folders, such as Mail, Safari data and the Trash. Unless Terminal has Full Disk Access (System Settings › Privacy & Security › Full Disk Access), du skips them with "Operation not permitted" and the totals are too low.

Where the space usually goes

Build output and dependencies

Xcode DerivedData, ~/Library/Developer/Xcode/DerivedData. Safe to delete; it rebuilds. See the DerivedData guide.
node_modules in every JavaScript project. Safe to delete; reinstall when needed. See the node_modules guide.
Rust target folders. Safe to delete; Cargo rebuilds them. See the Rust target guide.
Package manager caches for npm, Yarn, pnpm, Cargo, pip, Gradle and Homebrew. Safe to clear. See the caches guide. For Homebrew, brew cleanup -n shows what brew cleanup would remove.

Things that need a decision

iOS simulators, ~/Library/Developer/CoreSimulator. Remove runtimes in Xcode › Settings › Platforms rather than deleting folders.
Xcode Archives, ~/Library/Developer/Xcode/Archives. Keep archives of versions you shipped; they hold the symbols for their crash reports.
Docker, ~/Library/Containers/com.docker.docker. Its disk image can hold databases in volumes. Use docker system df to see usage and docker system prune to remove stopped containers, unused networks, dangling images and build cache. Never delete the disk image by hand.
Android emulators, ~/.android/avd. Delete them in Android Studio's Device Manager.
dist, build and out folders in projects. They may hold output you haven't deployed.

What "System Data" is

Storage settings put anything it can't categorize under System Data. That includes caches and logs, swap files, local Time Machine snapshots and app support files. Two parts are easy to check:

sysctl vm.swapusage
tmutil listlocalsnapshots /

Swap files live in /System/Volumes/VM and hold memory macOS moved to disk. Restarting clears most of them. Never delete them by hand. Local snapshots are managed by macOS, which removes them when it needs the space.

What to never delete

Anything under /System, /usr, /bin, /sbin or /private.
Swap files, or ~/Library as a whole.
~/.cargo/bin, ~/.rustup, global npm packages and your SSH and Git config.
Any folder you can't identify. Search for its name first.

Or let SymbolSweep find it

SymbolSweep covers the developer part of the problem. Its free scan measures, and lists by tier:

SAFE: npm, Yarn (~/.yarn/cache), Bun, Cargo registry, pnpm, pip, node-gyp, TypeScript, Homebrew, Go build and CocoaPods caches, plus .next, .turbo, .vite, .parcel-cache and node_modules/.cache inside projects.
REBUILD: Xcode DerivedData, Rust target folders, the pnpm store, Gradle and Maven caches, the Go module cache, Playwright browsers, .NET bin and obj, Unity Library and Unreal DerivedDataCache.
REINSTALL: node_modules.
REVIEW: Docker, Xcode Archives, iOS simulators and Android emulator images, listed with instructions only. Project dist, build, out and coverage folders can be moved to the Trash one at a time.
The macOS symbolication cache in ~/Library/Caches/com.apple.coresymbolicationd.

What it does not do: it doesn't clean System Data, swap, Time Machine snapshots, the Trash (beyond items it moved there itself), Photos, Mail, iCloud, iOS backups, app containers, or anything under /System, /Library or /Applications. It shows swap size for information only.

Download SymbolSweep for Mac

Scanning is free and never deletes anything. Deleting needs a one-time $12 license for one Mac. Requires macOS 13 or later on Apple silicon. See how it works.

FAQ

Why is System Data so large on my Mac?

System Data includes caches, logs, swap files and local Time Machine snapshots. On a developer's Mac, build tool caches in your Library often add to it. Check swap with sysctl vm.swapusage and snapshots with tmutil listlocalsnapshots /.

Is it safe to delete everything in ~/Library/Caches?

Most of it is regenerable, but some apps store data there they would have to download again, or sign you out. Delete specific folders you can identify rather than everything.

What is the quickest way to free space on a developer Mac?

Check Xcode DerivedData, node_modules in old projects, Rust target folders and package manager caches first. All of them are safe to delete and rebuild when needed.

Does SymbolSweep clean System Data or swap?

No. It cleans developer caches and build output in your home folder and the user-level symbolication cache. It doesn't touch swap, snapshots or anything under /System.