MPEG-4 Part 14 or MP4 file format, formally ISO/IEC 14496-14:2003, is a multimedia container format standard specified as a part of MPEG-4.
It is most commonly used to store digital video and digital audio streams, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images.
Like most modern container formats, MPEG-4 Part 14 allows streaming over the Internet. A separate hint track is used to include streaming information in the file. The official filename extension for MPEG-4 Part 14 files is .mp4, thus the container format is often referred to simply as MP4.
Some devices advertised as "MP4 players" are simply MP3 players that also play AMV video or some other video format, and do not play the MPEG-4 part 14 format.