A fast, free, and open-source disk space analyzer for macOS — an open alternative to DaisyDisk. Maps your drive as an interactive sunburst chart, scanning a full disk in seconds and streaming results live as it runs.
- Interactive sunburst chart, where each ring is one level deeper into the tree.
- Hover any slice to see its exact size, click to zoom into that folder.
- Sortable, Finder-style folder list beside the chart, with breadcrumbs.
- Results stream in live during the scan, so the chart and list fill in as it runs.
- Incremental rescans reuse the previous scan and replay filesystem events, so a repeat scan is 20–28x faster than a cold one.
- Understands APFS volume groups, firmlinks, purgeable space, and system volumes, so the total matches what your Mac reports as used.
- External drives appear automatically when connected.
The DaisyDisk-style sunburst you know — but free, open source, and faster.
| OpenDisk | DaisyDisk | |
|---|---|---|
| Price | Free | Paid |
| License | Open source (MIT) | Proprietary |
| Interactive sunburst | ✓ | ✓ |
| 1 TB cold scan | 17s | 37s |
Full scan of a 1 TB Apple Silicon volume, cold cache.
| Tool | 1 TB scan | Relative |
|---|---|---|
| OpenDisk | 17s | 1x |
| DaisyDisk | 37s | 2.2x slower |
| Baobab | 2m 15s | ~8x slower |
- macOS 26 (Tahoe) or later, on Apple Silicon or Intel.
- Full Disk Access, otherwise macOS hides parts of the filesystem and the totals come up short. Grant it in System Settings → Privacy & Security → Full Disk Access. The app prompts for it on first launch.
Open OpenDisk.xcodeproj in Xcode and run, or build from the command line:
xcodebuild -project "OpenDisk.xcodeproj" -scheme "OpenDisk" build- Launch OpenDisk and grant Full Disk Access when prompted, so nothing is hidden from the scan.
- Pick a drive, or choose Scan Folder… to analyze any directory.
- Explore the sunburst — hover a slice for its exact size, click to zoom in, and use the breadcrumbs or folder list to step back out.
- Open Purgeable Space to see caches and other reclaimable storage broken down.
- Reads directory metadata in bulk with
getattrlistbulk(2)andsearchfs(2)instead of onestatper file. - Uses a small number of concurrent readers (4–5 for subtrees, ~8 for a whole volume), since APFS serializes directory reads and throughput drops off past that point.
- Runs the blocking reads on a fixed pool of dedicated worker threads pulling from a shared work stack.
- Stops at mount points and snapshot volumes using a per-child mount flag, so scanning
/does not count the disk twice.
If you want, you can fork the code, make improvements and submit a pull request to improve the app. Accepting a PR is solely in the hands of the maintainer. Before making fundamental changes expecting them to be accepted, please consult the maintainer of the project first.
OpenDisk/
├── App/ App entry point
├── Models/ Folder items, chart data, scan progress
├── Services/
│ ├── DiskAnalyzer.swift Top-level scan orchestration
│ └── Scanning/ Scanner core
│ ├── ScanEngine.swift Strategy selection and streaming snapshots
│ ├── TraversalScanner.swift getattrlistbulk worker pool
│ ├── CatalogScanner.swift searchfs catalog scans
│ ├── ScanCache.swift Incremental rescan cache
│ └── SystemInterop/ Wrappers over the kernel APIs
├── Views/
│ ├── Charts/ Sunburst rings chart
│ ├── Analysis/ Results screen
│ └── Components/ Rows, breadcrumbs, status bar
└── Resources/ Assets and icons
Released under the MIT License.