JPEG 's conspicuous issues like lack of transparency, animation, lossless compression and high bit depth support makes it little tough to justify it as leading format for time to come. Various attempts like WebP and AVIF are made (and are supported on modern browsers) to overcome problems of JPEG but they all also suffer some shortcomings of their own. Rather than discussing it, let's see how is the web finally going to change with this new format - JPEG-XL.
JPEG-XL is what we believe is next 20 year format. Why?
It's not one but multiple reasons.
60-70% smaller size compared to similar quality JPEG 😮
Dimension of upto billion pixels allowed (JPEG-XL exclusive)
4099 channels support (JPEG-XL exclusive)
Animation support
Tile support for large images
Progressive decoding (see low resolution image first before full image loads - JPEG-XL and JPEG exclusive)
Lossless encoding support
Wide-color gamut support
Extremely fast for both encoding and decoding (WebP and AVIF are much slower)
Royalty free 🤘
This basically means anything that a photographer, developer or animation creator can think of, it's supported by this format. Everyone stays happy and gets to use one format for everything.
I can only answer the first part: .jxl