[ChrisMarshallNY]

1) End device has ability to display HiDPI images -> Send big

2) End device does not have ability to display HiDPI images -> Send small

Of course, if you have (1), in a low-bandwidth environment, then you actually want the server to send small, even if the device can handle big, but that can be indicated with a different flag.

[Hackbraten]

The `img` tag in HTML already supports that.

[ChrisMarshallNY]

Yes. But the same principle applies to things other than images. For example, regular PDFs, vs. optimized ones.