Your MP4 video captured with a mobile phone is inverted or played vertically when transferring it to your PC? This is a common occurrence on account of different aspect ratios between narrowscreen device and widescreen computer. In this case, the simplest solution is to rotate the MP4 file to the correct orientation by means of a free online video rotation tool. Here, this article draws up a list of 5 methods to rotate MP4 video online and appends a leading desktop MP4 rotator.