JPEG XL is a technically advanced image codec that improves on JPEG and offers more versatility than WebP. Despite its potential, it was notably rejected by Chrome in 2023, a decision that surprised many given its royalty-free status and backing by the JPEG Committee. Recently, a Rust-based JPEG XL decoder has been integrated into Firefox and Chrome in some form, prompting speculation that major web stakeholders might reconsider its adoption to mitigate vulnerabilities seen with WebP.
The author, an image compression expert with experience in video and AV1 encoding, explains why they chose not to develop an encoder for JPEG XL. The primary reason is that most web use cases rely on lossy compression, where JPEG XL does not outperform alternatives like AVIF. Its lossless compression advantage is marginal—around 12% smaller than lossless WebP on datasets not representative of typical web content—and thus insufficient to justify browser support.
JPEG XL's lossy compression efficiency lags behind modern encoders. Unlike AVIF, which benefits from directional prediction modes and advanced loop filtering to preserve edges and reduce artifacts, JPEG XL lacks these features. Its alternative approaches, such as spline-based edge preservation and patch coding, are more complex and less efficient. Additionally, JPEG XL struggles with non-photographic images, where AVIF's tools offer better performance.
In terms of decoding speed, JPEG XL is slower than competitors. Progressive rendering, a feature that allows early display of low-quality images during loading, is better implemented in AVIF. JPEG XL's decode times are longer, and certain crafted images can cause excessive decoding delays, posing risks for low-end devices.
The codec's broad feature set, including support for many channels and high color depths, is more suited to professional applications than typical web needs. The web prioritizes bandwidth efficiency, fast decoding, and simplicity, areas where JPEG XL currently falls short compared to AVIF and WebP.
The author concludes that while JPEG XL is valuable outside the web—such as in professional imaging workflows and camera systems—it is not a necessary addition to browsers at this time. The web benefits more from narrowly focused, efficient codecs like AVIF. The debate around JPEG XL is influenced partly by desires for more developer choice rather than clear technical superiority. Ultimately, JPEG XL may find its niche beyond the web rather than as a mainstream web image format.