Retina and HD screens have four times more pixels than standard screens. If you want to show a 48 x 40 icon, you need to use an 96 x 80 alternative to render it well on a high-density display, but you need to define the width and height of your icon in the fields above, otherwise the browser will render the icon in the bigger size automatically ( In this example you have to type 48 into the width and 40 into the height field ). Please use NUMBERS ONLY! If you do not care about retina screens, just upload your icon and leave the width and height fields empty.