Using the heights and sizes attributes

The heights and sizes attributes allow us to further tweak the display of our responsive images. The sizes attribute lets us use a media query to define how wide an image should be displayed, depending on the size of the user's viewport. Take the following code, for example:

sizes="(min-width: 640px) 50vw, 100vw"

This means that for screen sizes of 640 pixels and wider (min-width: 640px), the image should take up 50 percent of the viewport width (50vw). For all other screen sizes--that is--those less than 640 pixels, display the image at 100 percent of the viewport width: (100vw).

The heights attribute achieves a similar effect, but unlike sizes, it applies to the height of the image instead of the width, for example:

heights="(min-width:500px) 200px, 80%"