Without taking into account whether JPEG XL shines on its own or not (which it may or may not), JPEG XL completely rocks for sure because it does this:
.. $ ls -l a.jpg && shasum a.jpg
... 615504 ... a.jpg
716744d950ecf9e5757c565041143775a810e10f a.jpg
.. $ cjxl a.jpg a.jxl
Read JPEG image with 615504 bytes.
Compressed to 537339 bytes including container
.. $ ls -l a.jxl
... 537339 ... a.jxl
Do you realize how many billions of JPEG files there are out there which people want to keep? If you recompress your old JPEG files using a lossy format, you lower its quality.
But with JPEG XL, you can save 15% to 30% and still, if you want, get your original JPG 100% identical, bit for bit.
That's wonderful.
P.S: I'm sadly on Debian stable (12 / Bookworm) which is on ImageMagick 6.9 and my Emacs uses (AFAIK) ImageMagick to display pictures. And JPEG XL support was only added in ImageMagick 7. I haven't looked more into that yet.
This particular feature might not, but if said screenshots are often compressed with JPEG XL, they will be spared the generation loss that becomes blatantly visible in some other formats: https://invidious.protokolla.fi/watch?v=w7UDJUCMTng
But with JPEG XL, you can save 15% to 30% and still, if you want, get your original JPG 100% identical, bit for bit.
That's wonderful.
P.S: I'm sadly on Debian stable (12 / Bookworm) which is on ImageMagick 6.9 and my Emacs uses (AFAIK) ImageMagick to display pictures. And JPEG XL support was only added in ImageMagick 7. I haven't looked more into that yet.