The ideal of an image format the can progessively support different sizes was discussed back when solutions to the responsive image issue were first being sough

The ideal of an image format the can progessively support different sizes was discussed back when solutions to the responsive image issue were first being sought out e.g. https://blog.yoav.ws/posts/responsive_image_container/ https://blog.yoav.ws/posts/responsive_image_container/ JPEG 2000 already offers the ability to encoded multiple sizes of an image in the same file https://www.verypdf.com/pdfinfoeditor/jpeg-jpeg-2000-comparison.htm https://www.verypdf.com/pdfinfoeditor/jpeg-jpeg-2000-compari... I think there was some hope that JPEG XL might be able to meet this need too