The srcset attribute

What is the main benefit we can gain from the use of this attribute? Thanks to it, web developers can target users on high-resolution displays with a high-resolution image source or different types of screens with other versions of images. In the first case users on lower pixel density displays won’t be saddled with the wasteful bandwidth cost of downloading a useless massive high-resolution image, while the latter can enjoy the power of their screen. In the second situation, we can specify a different image for different screen sizes, in order to provide an image that is more focused on the users’ device.

Responsive Images, Part 1: Using srcset – SitePoint.