While Firefox 152+ already offers experimental JPEG-XL support, Mozilla formally announced today their plans for officially shipping JPEG-XL image format support in the Firefox web browser.

For Firefox 157, which is due for release at the end of September, the plan is to enable JPEG-XL image decoding by default on all available platforms. Firefox Nightly has JPEG-XL support enabled by default right now to help in vetting this support while Mozilla believes the support is in good enough shape for a stable debut with Firefox 157.

This follows Chrome shipping JPEG-XL and Google Research developing jxl-rs as a Rust-based JPEG-XL image decoder that is both performant and secure.

In today's Mozilla Hacks blog post they elaborate on JPEG-XL vs. AVIF image formats:

"JPEG XL: Excels at lossless imagery, progressive rendering, and further compressing JPEGs without quality loss.

AVIF: Excels at web-quality photographic images, and images that have a mix of sharp edges and flat surfaces.
...
Although AVIF tends to produce smaller files at web-quality than JPEG XL, AVIF only has basic progressive rendering support. So, for very large images, it may be worth taking the filesize hit with JPEG XL."

More details on the JPEG-XL Firefox plans via this mailing list post.

Google today also formalized their intent for shipping JPEG-XL decode in the Blink engine for all users by default.