A website can be viewed in a wide variety of resolutions and formats, some dictated by the size of a desktop display, and others by the specific dimensions of a phone or tablet model. Device rendering provides a preview of how the site looks on some popular device resolutions to help identify obvious issues. Note, our method will load a website and resize it's portlet to several dimensions, as opposed to loading the site multiple times directly in different devices.
In general a website should be designed and tested to be responsive across a large variety of desktop and mobile device resolutions, as well as being able to transition smoothly (for example when resizing a browser or flipping a tablet from vertical to horizontal).