losslessly
The facts below are what the maker publishes about losslessly, checked and dated. Our editors have not written about it yet.
The facts
Each one read from losslessly's own pages, with the date it was checked.
What it does
- Automation
- The --check option writes nothing and exits with code 1 if any file could shrink, enabling CI checks.checked 4 Oct 2026
- CI and hooks
- A --check mode can fail CI when files could shrink, and the README shows integration with lefthook pre-commit hooks.checked 12 Oct 2026
- Data handling
- The README describes processing local files in place and replacing a file only when the result is smaller.checked 4 Oct 2026
- Formats
- It searches directories recursively for PNG, APNG, JPEG, GIF, WebP and SVG files, with extensions in either case.checked 12 Oct 2026
- GIF limit
- It leaves a GIF alone when its frames exceed the supported palette color count or when a frame turns opaque pixels transparent again.checked 12 Oct 2026
- Image integrity
- PNG, JPEG and WebP output decodes to the same pixels as the input, while GIF output preserves rendered frames and timing.checked 4 Oct 2026
- In-place optimization
- It replaces a file only when the optimized result is smaller and otherwise leaves it byte-for-byte untouched.checked 12 Oct 2026
- Installation
- Prebuilt binaries are offered for macOS and Linux on x86_64 and arm64, and Windows on x86_64; it can also be installed with Cargo.checked 12 Oct 2026
- Integrity checks
- It checks file magic bytes against extensions and reports decoding errors without changing files it cannot process.checked 12 Oct 2026
- License
- The repository is released under the MIT license.checked 12 Oct 2026
- Lossless behavior
- PNG, JPEG and WebP output decodes to the same pixels as input, while GIF output preserves rendered frames and timing.checked 12 Oct 2026
- Metadata
- EXIF, ICC profiles, XMP and comments are preserved unless the --strip option is used.checked 12 Oct 2026
- Notable limits
- It does not do lossy compression or format conversion, and AVIF and JPEG XL are not on its roadmap.checked 4 Oct 2026
- Product
- losslessly is a command-line tool that recompresses PNG, JPEG, GIF and WebP files and minifies SVG markup.checked 12 Oct 2026
- Purpose
- losslessly is a command-line image optimizer that recompresses PNG, JPEG, GIF and WebP files and minifies SVG markup.checked 4 Oct 2026
- Safety
- Writes use a temporary file in the same directory and rename it over the original, so the original remains if the process dies mid-write.checked 12 Oct 2026
- Scope
- Lossy compression and format conversion are out of scope, and AVIF and JPEG XL are not on the roadmap.checked 12 Oct 2026
- Source install
- Source installation requires a Rust toolchain and C compiler.checked 4 Oct 2026
- SVG precision
- SVG output uses svgo's default numeric precision, so it does not have a bit-level guarantee.checked 12 Oct 2026
- Tuning
- PNG compression supports effort levels 0–6, and the optional Zopfli mode is slower but produces somewhat smaller files on most images.checked 12 Oct 2026
- WebP limit
- It skips lossy and animated WebP files; only lossless still images are re-encoded.checked 12 Oct 2026
The company
- Maker
- The GitHub profile identifies the maker as Kamil Doroszewicz and lists Poland as the location.checked 4 Oct 2026
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