macOS · Storage
“System Data: 187 GB”
is not an explanation.
It is macOS telling you it has 187 GB of things it could not put in any other bucket. Caches, logs, snapshots, developer tooling, an iOS backup from a phone you no longer own. The storage bar cannot break it down, so the first real step is not deleting anything — it is finding out.
Free to try, no account required.
Why the storage bar cannot help you
System Data is a leftovers category
Anything macOS cannot confidently label as a document, an app or a photo lands there. It is not one thing, so there is no one thing to delete — and the label tells you nothing about which part is large.
Finder will size one folder at a time, slowly
Get Info on a folder works. Doing it for every folder on a 1 TB disk is not a plan. Without size by directory, sorted, you end up guessing at what is big — and guessing is how people delete the only copy of something.
The advice online is mostly for a different Mac
Clear your caches, delete your Xcode DerivedData, empty the Trash. Fine if you are a developer with a full Trash. Useless if you are not, and you have spent an evening finding out.
Snapshots make space appear and disappear
Time Machine keeps local snapshots and thins them when the disk gets tight. So free space moves on its own, deleting a large file sometimes frees nothing immediately, and the whole thing feels haunted.
Finding out, then acting
Storage breakdown by folder
Size by directory, sorted, so the answer arrives in one look instead of an evening. Almost always three or four folders hold most of what you cannot account for, and once you can see them the decisions make themselves.
The large files, ranked
Disk images, video exports, virtual machines, installers you kept. The fastest gigabytes to recover are usually a dozen files rather than a thousand small ones.
Space Saver, for the caches worth clearing
Browser caches, developer tooling — Xcode derived data and archives, npm, yarn, pip, Cargo, CocoaPods, Homebrew, Swift Package Manager, simulator caches — plus Slack, Discord, Zoom, Spotify and user logs. Each category is scanned and sized before anything is removed.
Rated by consequence, not just by size
Categories carry a rating. Safe ones can go without you thinking about it; conditional ones cost you something real — a slower next launch, a re-download — and are reported rather than swept up. The ones that would break something are not offered at all.
Duplicates, matched by content
The same file under four names across three folders is invisible to anything comparing filenames. Content matching finds it, and nothing is deleted by default — duplicates move to a folder you nominate.
Then keep it from coming back
Organizing a folder is reversible and makes the next clean-up an hour’s work instead of an evening’s. The mess is usually three folders; sorting them is what stops this being annual.
What it does not do yet
- — System-level cleanup needs the privileged helper installed. Without it, VaultSort still reports what is there and cleans everything at the user level — which is where most recoverable space actually is.
- — Deletion is gated by a generated allow-list, so the scanner can occasionally show you a path the cleaner then declines to remove. That is the safe direction for the error to point, and the refusal is reported rather than hidden.
- — Local snapshots are macOS’s business. VaultSort will show you what they cost and will not thin them for you — that is Time Machine’s job, and doing it behind your back is how backups go missing.
- — Space freed can take a moment to appear. macOS reclaims lazily, and a disk that was under pressure may release space in stages.
Questions people ask
Is it safe to delete cache files?
Most of them, yes — a cache is by definition rebuildable. The cost is the rebuild: a browser cache means slower first loads, a developer cache means a slower next build. That is why the categories carry a rating and the ones with real consequences are reported rather than cleared for you.
Why does my Mac say the disk is full when I have deleted things?
Usually local snapshots, which macOS thins on its own schedule rather than the moment you need the space. It is also worth checking whether the file you deleted is still in the Trash, or still held open by a running app.
Will this delete anything I need?
The intent is that it cannot. Categories that would break something are not offered, deletion is gated by an allow-list, and duplicates move rather than disappear. Where something is out of reach, it is reported as refused instead of counted as done.
How much space will I get back?
Nobody can tell you honestly before scanning, and anyone quoting a number is quoting an average. Measure first — the scan is free, and the figure it gives you is about your Mac rather than about someone else’s.
Try it on your own files
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