Pixel Density
Device pixel ratio dpr
The device pixel ratio is used to easily convert between CSS pixels and device pixels. This makes it possible to display images at the correct pixel density on a variety of devices such as Apple devices with Retina Displays and Android devices. You must specify either a width, a height, or both for this parameter to work. The default is 1. The maximum value that can be set for dpr is 8.
<img src="kayaks.jpg?w=250&dpr=2">
