I built SDTally because "System Data" in macOS Storage settings is a number with no explanation. On my Mac it was about 166 GB, and the biggest single item was roughly 19 GB of video files that a code editor's language server had copied into a bin/ folder. A tool that only checks a fixed list of cache folders would never look there. It is a Rust command-line tool that measures the whole Data volume, plus a SwiftUI app that shows the result. It splits the number into parts, says which app owns each folder, shows where every number comes from, and labels what it couldn't measure as "unexplained" with the reason. With root and Full Disk Access that is about 2% of used space: folders Apple blocks even root from accessing. It keeps a history, so you can see what changed since last time. Version 1.0.3 also finds identical copies of large files (compared byte by byte, never deleted) and marks sparse and compressed files in the largest files list. It never deletes or moves anything and it doesn't use the network. Recommendations are text, and the app never runs them. Stage: 1.0 released on Oct 21 (now v1.0.3), free and open source (GPL-3.0-or-later). Apple Silicon and macOS 15+ only. The DMG is not notarized because I don't have a paid Apple developer account, so the first launch needs Privacy & Security > Open Anyway. I built it with a lot of help from Claude Code and the commits show it. Screenshots are in the README (they use sample data): https://github.com/guiselig/sdtally#screenshots Repo: https://github.com/guiselig/sdtally One thing I'd like to know: when you read the "unexplained" line, is it clear what it means and why it is not zero? That's the part I'm least sure I explained well.   submitted by   /u/Seliguinho [link]   [comments]