Image: github.com · The System Data section: the number from Storage settings broken down into measured parts, each with its source
SDTally, an app that measures what fills macOS System Data
A macOS app built with Claude Code that splits the System Data figure into measured parts and shows what it cannot explain.
Credits
- Reddit poster Seliguinho Source ↗
- Repository account guiselig Source ↗
Earliest dated source:
The full story
macOS "System Data" is whatever is left after other categories are assigned, so there is no folder to open. On the poster's Mac, the biggest item was about 19 GB of video files copied by a code editor's language server into a bin/ folder, which a fixed list of cache folders would miss.
SDTally measures the whole Data volume and splits it into parts with sources, counting allocated blocks and APFS clones once. What it cannot measure is shown as "unexplained", about 2% with root and Full Disk Access. It is read-only and built with Claude Code; the code is on GitHub.
How it was done
Tools
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Sources
From a short post by the maker, so the details are as they tell them.
- Reddit: I built an app with Claude Code that explains macOS "System Data" by measuring itReddit poster: SeliguinhoPosted
The maker's reply in r/ClaudeAI's showcase thread.
If it disappears: archived copy of Reddit: I built an app with Claude Code that explains macOS "System Data" by measuring it (opens in a new tab)
- The code: github.comRepository account: guiselig
Linked from the post.