Because both file elements are compressed, MP4s normally have a smaller file size than many other video formats, but still maintain relatively high quality for sharing online. The video part is usually compressed with MPEG-4, and the audio is usually compressed using AAC, which is the audio format associated with iTunes. MP4 videos are made up of video and audio elements that are compressed separately. MP4 is usually the preferred format for uploading videos to YouTube, Vimeo or other websites.
As MP4 is a standardised format, it will normally play easily on most devices and media players, including Windows Media Player, QuickTime, and VLC. It was originally developed by the Moving Picture Experts Group (MPEG) but has become an ISO standard, meaning that it’s now maintained by the International Organisation for Standardization. MP4 was developed to be easily played and shared.
MP4, sometimes called MPEG4, is one of the most common video formats.