Looks like yes [1] >A lightweight lossless conversion process back to JPEG ensures compatibility with existing JPEG-only clients such as older generation phone

Looks like yes [1] >A lightweight lossless conversion process back to JPEG ensures compatibility with existing JPEG-only clients such as older generation phones and browsers. Thus it is easy to migrate to JPEG XL, because servers can store a single JPEG XL file to serve both JPEG and JPEG XL clients. [1] https://jpeg.org/jpegxl/index.html https://jpeg.org/jpegxl/index.html