tl;dr: An image compression engineer argues against adding JPEG XL to browsers, contending that modern AVIF encoders now beat it on lossy compression efficiency across the fidelity range, while its ~12% lossless advantage over WebP isn't worth the added complexity. JPEG XL also decodes significantly slower than alternatives, lacks progressive rendering parity with AVIF, and its expressive spec enables "JXL bomb" attacks on low-end devices. The author concludes JPEG XL is impressive tech better suited to professional/non-Web use cases, and that much of its browser advocacy is driven by anti-Google sentiment rather than technical merit.