Firefox will enable JPEG XL decoding by default across platforms with the release of Firefox 157, rolled out from the existing image.jxl.enabled setting which is already on by default in Nightly and available via Firefox Labs for other channels.

A stable debut is targeted by the end of September 2026, with Nightly continuing to validate the feature ahead of that rollout.

Firefox Nightly currently uses JPEG XL by default to vet the feature before broader release.

The change has passed TAG review, indicating alignment with W3C TAG design considerations.

discussions reference Bugzilla, design reviews, and external tools and benchmarks to justify decisions.

JPEG XL aims for parity with other image formats and Blink’s JXL, featuring HDR tone mapping that yields SDR-like display, with Safari supporting progressive rendering and animation and Chrome behind a flag; Firefox plans broader support.

Feature parity includes animation and progressive display; HDR tone mapping is stronger than in other formats, but HDR images render as SDR.

There is debate over lossless JPEG XL performance, with concerns it may be slower than lossless WebP; recommendations consider shipping only lossy JPEG XL and evaluating lossy as a separate path.

Benchmarks show JPEG XL decoding is slower than WebP lossless in some cases but faster in others, with real-world battery and performance impact under discussion.

The decoding implementation uses the jxl-rs Rust library, with prototypes progressing and multithreaded decoding improved in jxl-rs 0.6.0.

WPT tests cover decode correctness across depth and color variations, while Gecko tests add chunked decoding, progressive rendering, and performance telemetry, with full test suites and Perfherder reporting planned.

A comprehensive testing regime (wpt/jxl and Gecko) assesses decode correctness, color management, orientation, and performance, with fuzzing continuing before the preference is flipped.