How to Free Up Disk Space on a Mac (the developer's playbook)

By the maker of WTMemory · Tested on macOS Sequoia · Updated Sept 2026

Mac storage reporting has a confession to make: the "Available" number it shows you is a negotiation. Half the space macOS claims is "purgeable" isn't actually free until the system decides it wants it, and the things that genuinely fill a developer's disk - build artifacts, AI model weights, snapshots - are invisible in About This Mac → Storage. Here is what actually works, in the order that gives you the most gigabytes per minute.

1. Find what is really using the space

Finder's storage screen groups by file type, which is useless for dev machines. Run this instead:

du -sh ~/Library/Developer/Xcode/DerivedData ~/.ollama ~/.cache ~/Library/Caches 2>/dev/null

On a typical machine that has seen a year of Xcode and a weekend of "just trying" local LLMs, expect 10-60 GB of answers.

2. Delete the stuff that regenerates

• Xcode DerivedData (~/Library/Developer/Xcode/DerivedData) - pure build cache. Safe to delete; your next build just re-indexes (slower first build, then normal).
• Package caches - ~/.npm/_cacache, ~/Library/pnpm/store, ~/.cargo/registry, ~/.gradle/caches. Re-downloaded on the next install.
• Local AI models - ~/.ollama/models, ~/.cache/huggingface, ~/.cache/lm-studio. The biggest single win for anyone who ever ran a 7B model "once". They re-download when you need them.
• Simulator runtimes - xcrun simctl delete unavailable prunes the dead ones.

3. The trick nobody tells you: purgeable space is Time Machine

That "purgeable" number in Storage settings is mostly local Time Machine snapshots, and macOS will happily wait days before "purging" them. Force the issue:

tmutil listlocalsnapshots /
sudo tmutil thinlocalsnapshots / 999999999999999 4

Then check df -h /. On machines that haven't been rebooted in weeks, this alone often frees 5-30 GB that every "cleaning" app claims to have found.

4. Empty the Trash (it is not automatic)

Deleted files sit in ~/.Trash counting against you until you empty it. Yes, really - the #1 "why is my disk still full after deleting 20 GB" answer.

5. What NOT to delete

• ~/Library/Mail, Messages data, Photos library - these are your actual data.
• Anything Apple-prefixed in system locations you found via a random blog.
• APFS snapshots taken by an in-progress backup - the thinning command above handles this safely; manual rm does not.