September 1, 20262 min read

The hidden caches actually worth clearing on your Mac

Most 'cleaner' lists pad their numbers with files you'd never miss. These are the caches that genuinely eat tens of gigabytes — and are safe to clear.

GuidesStorageDeveloper

If you've ever googled "free up disk space on Mac", you've seen the lists: delete your Downloads folder, empty the Trash, move photos to an external drive. All true, none surprising. Meanwhile the real space hogs sit in folders Finder won't surface and Spotlight mostly ignores.

Here are the caches that routinely hold tens of gigabytes, and why clearing them is safe.

#Xcode DerivedData

Every Xcode build writes intermediate products — compiled indexes, build logs, symbols — into ~/Library/Developer/Xcode/DerivedData. Xcode never prunes this on its own. On an active project it's common for a single app to leave 5–15 GB behind, and most developers carry several projects.

Clearing it is completely safe: the next build simply recompiles from scratch and takes a little longer, once.

# What's in there?
du -sh ~/Library/Developer/Xcode/DerivedData/* | sort -h

#Homebrew caches

Homebrew keeps every version of every formula it has ever downloaded:

brew cleanup -s          # scrub old downloads and stale versions
brew cleanup --prune=all # go further: remove even recent caches

The download cache alone (~/Library/Caches/Homebrew) frequently grows past 10 GB on machines that have run brew upgrade a few dozen times. Nothing installed depends on it.

#Simulator runtimes and device data

iOS simulator devices accumulate app installs, media and logs per runtime. xcrun simctl delete unavailable removes devices tied to runtimes you no longer have. Unused runtimes themselves can be managed in Xcode → Settings → Platforms, and each one is 5–8 GB.

#Browser and app caches — the honest caveat

Browsers, Slack, Spotify and friends cache media under ~/Library/Caches. Clearing these is safe but low-yield: they rebuild within days and usually stay under a few gigabytes. Any tool promising "50 GB recovered" from browser caches is counting files that come straight back.

A good rule: clear caches that rebuild from the network in minutes, but never delete anything in ~/Library you can't name.

#The quick version

Cache	Typical size	Safe to clear	Rebuild cost
Xcode DerivedData	5–15 GB per project	Yes	One slower build
Homebrew downloads	5–20 GB	Yes	Re-download on next install
iOS simulator devices	2–10 GB	Yes	Fresh simulator
Browser caches	0.5–3 GB	Yes, but futile	Days of re-downloading

MacVoid finds all of the above in one scan, shows the list before anything moves, and only ever puts files in the Trash — so every cleanup is reversible.

#Keep going

This guide is part of our storage series. For the complete playbook, read how to free up space on your Mac, or see why your Mac's storage graph lies to understand where all that "System Data" comes from.