Comment by F3nd0

Yes. My understanding is that AV1 encoders have been continuously improving, while JPEG XL lost a lot of drive and manpower for a couple of years since its future on the web became uncertain, allowing AV1 to get ahead. That’s probably an important factor.

In particular, I don’t think there was significant progress on compression between libjxl v0.10.0 and v0.12.0, and there some regressions from earlier versions still remain. The article also measures the quite recent jixel, which is derived from the older libjxl-tiny and apparently does better in many cases. So JPEG XL encoders definitely have lots of room for improvement. With JPEG XL finally gaining wider adoption on the web, perhaps they’ll catch up or get ahead again. AV1 encoders are also still being improved, though.