You can easily mock up your web prototypes for high-resolution displays, commonly known as retina or high DPI.

InVision will display any image at 50% - doesn’t matter if it's a screen or a background – and all you have to do is use the modifier @2x in your filename. For example: file_name@2x.png

Note: Use only when necessary as full page high-resolution images may double your prototype's loading time and viewing on slower internet connections may be slower. 

Learn more about InVision and @3x here.