If Jpeg-XL was backwards compatible with older clients, it would probably take off. Like if the format embedded a standard jpeg image in the front readable by older clients, and then enhanced it with additional data at end of file readable by Jpeg-XL clients.
You could compress the hell out of the traditional jpeg codec/layer part of the image. It’d be there for backwards compatibility. It only has to be readable by older clients and “acceptable” quality.
See “49kb” example here — totally acceptable image quality for backwards compatibility.
JPG-XL crying in the corner.
Sitting next to JPEG-2000
If Jpeg-XL was backwards compatible with older clients, it would probably take off. Like if the format embedded a standard jpeg image in the front readable by older clients, and then enhanced it with additional data at end of file readable by Jpeg-XL clients.
That’d just be overall worse, it’d never be smaller than a comparable JPEG image, and it wouldn’t allow for any compression/quality benefits.
You could compress the hell out of the traditional jpeg codec/layer part of the image. It’d be there for backwards compatibility. It only has to be readable by older clients and “acceptable” quality.
See “49kb” example here — totally acceptable image quality for backwards compatibility.
https://res.cloudinary.com/thewebmaster/image/upload/c_scale,f_auto,q_auto,w_1250/images/blog/jpeg-images-definitive-guide/JPEG_Quality_vs_Size.png