The WebM video format is mainly intended for playing HTML5 video. WebM video quality is roughly similar to MP4, and its size is much smaller. However, if you want to play WebM movies in mobile browsers or other media players, you must convert the WebM format to MP4. Converting WebM to MP4 is not a difficult task. You can read this post to download a free WebM to MP4 converter or professional video converters that will allow you to convert the MP4 file in high quality.