I just had my responsive images epiphany and I'm writing it all down before I forget everything. This is what I know… Fixed size, varying density If your image is a fixed size in pixels, but you want to cater for screens of different density, here's the solution: <img alt="A cat" width="320" height="213" src="cat.jpg" srcset="cat-2x.jpg 2x, cat-3x.jpg 3x">Fixed size, here or in CSSThis is used as