Viewport Height Media Header
All the media header widgets have a viewport height option. This is selected by checking a box and sets the height to 100vh. This means that the item will fill the browser or device window - no matter what size it is.
Those who are used to creating fixed width websites using pixels as a unit of measure will probably be unfamiliar with using percentages and viewport units.
Viewport Unit
A viewport unit is similar to a percentage in that it is relative unit of measure rather than an absolute one like a pixels. Using relative units is a requirement for laying out the elements in a responsive web design.
A viewport unit is equal to 100th of the screen or browser width or height.
Viewport Height (vh) is based on the height of the viewport. A value of 1vh is equal to 1% of the viewport height.
Viewport Width (vw) is based on the width of the viewport. A value of 1vw is equal to 1% of the viewport width.
By setting the header at 100% in width and 100vh in height, it fills the browser or device window.