To change the video format to MP4 on a smartphone, you need to use an iOS- or Android-based video to MP4 converter, such as Video Converter, Compressor, and Video Format Factory. The steps to convert videos to MP4 with different applications on smartphone are almost the same. 1. Load the original video file to the video to MP4 converter. 2. Set MP4 as the output format. 3. Hit Run or Start to launch the conversion process.