Firefox will enable JPEG XL decoding by default across platforms with Firefox 157, activated through the image.jxl.enabled preference, which is already on by default in Nightly and accessible via Firefox Labs on other channels.

The TAG review found the change satisfactory, noting alignment with design considerations despite certain concerns raised in the W3C TAG design review.

The feature aims for parity with other image formats and rival implementations, including animation and progressive display; HDR tone mapping is notably strong, though HDR content is presented as SDR.

The standard referenced is ISO/IEC 18181, with ISO/IEC as the standards body, and Mozilla maintains a neutral position on standards per its standards-positions page.

Prototype discussions were shared publicly, and browser adoption varies: Safari shipped JPEG XL in 2023 with version 17.0, while Chrome currently uses the same Rust library behind a feature flag.

Web Platform Tests cover decode correctness across bit depths, alpha, grayscale, CMYK, color management, orientation, and coding tools; Gecko tests cover chunked/incremental decoding, animation frame counts, downscaling during decode, handling of corrupt files, progressive rendering, telemetry, reftests, and decode benchmarks reported to Perfherder.

The JPEG XL decoder in use is jxl-rs, implemented in Rust, with the change tracked under Bugzilla bug 2065096.

Performance work includes jxl-rs 0.6.0 bringing multithreaded decoding, with upcoming patches to land, and benchmarks show Firefox ahead of Safari on large images and competitive on large vs. Safari, with a larger gap on small images.

Fuzzing for JPEG XL was conducted before nightly enablement and will be repeated before flipping the preference.