Native, offline, drag-and-drop image compression for the Mac. Squoosh-class savings, ImageOptim simplicity, native SwiftUI.
- Drag and drop a batch of images and compress them all at once.
- Live size estimate before you commit: it runs a real file through the actual compression pipeline (not a guess) and extrapolates to the batch, debounced and cached so dragging a slider stays smooth.
- Compression runs in parallel, bounded to your CPU core count, with working cancellation mid-batch.
- Compressed files land in place, keeping their original names and folder, so nothing downstream has to be re-linked or renamed. Before any of that happens the untouched originals are preserved in an
Uncompressed Backupfolder alongside them. No exporting to a second folder, no swapping files back by hand, nophoto-compressed-final.png. - Never makes a file worse: if the compressed output isn't smaller than the original, the original is left alone and the result is reported as "Already optimized." Explicit format conversions (say, PNG to WebP) always deliver, even if the converted file happens to be larger.
- PNG, JPEG, WebP, and AVIF, including conversion between the four and resolution scaling.
- AVIF output via ImageIO, no external tools. It is offered only when this Mac's ImageIO can actually encode it, checked at runtime. AVIF input decodes everywhere macOS 15 does.
- Writes go to a temp file first. In-place compression then replaces the original atomically, so a crash or kill mid-run can't leave a half-written file.
- If pngquant or cwebp aren't installed, Crunch tells you inline and gives you the install command instead of failing silently.
scripts/make-app.sh
This builds a release binary and assembles dist/Crunch.app, ad-hoc signed and ready to run. Not notarized; running it the first time requires right-click → Open, or removing the quarantine flag.
Prerequisites for PNG and WebP compression:
brew install pngquant webp
JPEG compression works with zero external dependencies, it uses ImageIO natively.
PNG compression shells out to pngquant, WebP to cwebp. Both are located at runtime by checking /opt/homebrew/bin, /usr/local/bin, and /opt/local/bin in order, then falling back to a PATH scan. JPEG and AVIF are handled entirely in-process via ImageIO, no subprocess involved.
Every compression writes to a temp file first. Before any of that happens, the batch is copied to Uncompressed Backup in the same folder as the originals.
Compressing a file in its existing format then atomically replaces it (FileManager.replaceItemAt), so a partial write never corrupts a source file. Converting to a different format is not an in-place replace: the output moves to a new path picked up front and guaranteed not to collide with anything already on disk or with another file in the same batch, and only then is the source deleted. A crash between those two steps leaves both files, never neither.
swift run # launch the app
swift test # run the test suite
The package splits into a CrunchCore library (models, services, utilities: the compression pipeline, backup, tool discovery) and a Crunch executable (SwiftUI views and view models). CrunchTests covers CrunchCore with Swift Testing; the PNG and WebP suites skip automatically when pngquant/cwebp aren't on the machine running the tests, which is the expected state in CI.
Requires macOS 15+ and Swift 6.
MIT, see LICENSE.