Last week I found AI coding tools hiding 32 GB on my MacBook. Claude, Codex, Cursor and Gemini were all sitting inside the grey "System Data" bar that macOS won't let you open.
So I kept going. The next biggest thing in there wasn't an app at all. It was Homebrew: 25.6 GB in /opt/homebrew.
I don't think of Homebrew as big. You type brew install, something appears, you move on. But every install leaves things behind, and a few of them are enormous.
Anaconda: 9.17 GB, and 5.21 GB of it is a cache
I installed Anaconda once for a data course. It's still here: 9.17 GB, plus an 882 MB copy of its installer that Homebrew keeps.
More than half of that, 5.21 GB, is anaconda3/pkgs: a copy of every package conda has ever downloaded, kept so the next install is faster. Your environments don't need it.
conda clean --all
That removes the cached packages and tarballs and leaves your environments alone. If you don't use conda anymore at all:
brew uninstall --cask anaconda
That's the whole 9.17 GB plus the installer copy.
Flutter: 4.1 GB
The Flutter SDK lives in /opt/homebrew/share/flutter. If you build Flutter apps, keep it. If you tried it once, brew uninstall --cask flutter gives back 4 GB.
Three Java versions: about 1 GB
I had openjdk, openjdk@17 and openjdk@11 installed side by side. Before removing an old one, check what still depends on it:
brew uses --installed openjdk@11
If that prints nothing, it's safe to brew uninstall openjdk@11.
Things you installed once and forgot
Hadoop (1.59 GB), MongoDB, Pandoc, Go. Each one was a reason at the time. This lists only the packages you installed, not their dependencies, which makes forgotten ones easy to spot:
brew leaves
The two commands everyone should run
brew cleanup --prune=all # old versions and every cached download
brew autoremove # dependencies nothing needs anymore
Neither touches anything you still use.
Why macOS calls this "System Data"
/opt/homebrew isn't in your home folder, so macOS's Storage settings can't put it under Apps or Documents. It goes into System Data, alongside app caches and AI models. On my Mac, "Shared Library & Homebrew" alone was 32 GB of the 147 GB System Data bar.
The rule I follow now: caches are always safe, SDKs you don't use are the biggest wins, and anything with your data in it is a decision you make on purpose.
I build Tidy Mac, which is how I measured all of this. It breaks System Data into named parts like this one, and anything you clear goes to the Trash first. The commands above work without it.
Drafted with AI assistance. Every number was measured on my own Mac.
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