JPEG-XL image support is moving from experimental to a stable feature in Firefox. Mozilla has formally announced its intent to enable JPEG-XL decoding by default across all platforms with the release of Firefox 157, scheduled for late September. This decision marks a turning point after years where the format was only available behind an experimental flag, a choice driven by concerns regarding the attack surface of the original C++ decoder.

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The security breakthrough with a Rust decoder

The critical blocker that prevented JPEG-XL adoption in Firefox for years was the complexity of the source code: approximately 100,000 lines of multithreaded C++ represented a significant security risk for the browser. The solution came from Google Research, which developed jxl-rs, a Rust-based decoder. This rewrite in a memory-safe language allowed Mozilla to overcome its reservations, making the format ready for a stable debut without compromising platform integrity.

Firefox 152 Now Available With JPEG-XL Support Built By Default ... — https://www.phoronix.com/news/Firefox-152-Download

JPEG-XL vs. AVIF: the strategic choice for web developers

In its official Mozilla Hacks post, the development team outlined the practical differences between JPEG-XL and AVIF for web developers. While AVIF excels in compressing web-quality photographic images and produces smaller files, JPEG-XL stands out for its lossless rendering and advanced progressive decoding. For very large images, Mozilla suggests that the slight increase in file size with JPEG-XL is an acceptable trade-off for smoother, progressive visualization compared to AVIF's basic support.

Alignment with Chrome and the impact on the modern web

Mozilla's move coincides with Google's decision to formalize JPEG-XL decoding in the Blink engine for all Chrome users. With both major browsers converging on this standard, the web is preparing for a significant transition in image formats. For end users, this means sharper images and optimized loading; for web developers, the opportunity to leverage a format that surpasses WebP and traditional JPEG in terms of efficiency and visual quality.