jxl-rs https://github.com/libjxl/jxl-rs was referenced as a possibility; what li...

JimDabell · 2025-11-23T11:37:02 1763897822

libjxl:

gsnedders · 2025-11-24T16:47:06 1764002826

The second link isn't applicable to Apple's WebKit ports — it's entirely built via Xcode.

https://github.com/WebKit/WebKit/blob/39386f4547897c89c510d0... defines USE_JPEGXL only for macOS < 14 (which aren't actually supported any more!).

All the in-tree JPEG XL support, e.g., https://github.com/WebKit/WebKit/blob/39386f4547897c89c510d0... is behind a "USE(JPEGXL)" ifdef — so none of that is compiled in.

Instead, it's using what Apple ships at a system level, in Image I/O.

https://github.com/WebKit/WebKit/blob/39386f4547897c89c510d0... defines HAVE_JPEGXL for recent versions of Apple's OSes. https://github.com/WebKit/WebKit/commit/932073284e4c73ce9884... is the commit which added this — there's really not much there, because it's just setting the define and adding it to the allowlist of image types.

And yeah, currently I believe this is libjxl — or a fork thereof — hence the inclusion of libjxl in the Acknowledgements.rtf file on macOS.