M3U is a computer file format for a multimedia playlist.
Although originally designed for audio files, such as MP3, it is commonly used to point media players to audio and video sources, including online sources. M3U was originally developed by Fraunhofer for use with that company's Winplay3 software, but numerous media players and software applications now support the format.
There is no formal specification for the M3U format; it is a de facto standard.
An M3U file is a plain text file that specifies the locations of one or more media files. The file is saved with the "m3u" filename extension if the text is encoded in the local system's default non-Unicode encoding (e.g., a Windows codepage), or with the "m3u8" extension if the text is UTF-8 encoded.
Each entry carries one specification. The specification can be any one of the following:
- an absolute local pathname; e.g., C:\My Music\Heavysets.mp3
- a local pathname relative to the M3U file location; e.g. Heavysets.mp3
- a URL.
- A folder name - all the mp3 files inside will be played.
- comments are prefaced by the "#" character.
In extended M3U, "#" also introduces extended M3U directives.
- #EXTM3U File header. Must be the first line of the file.
- #EXTINF Track information, including runtime and title.
- for example: #EXTINF:191,Artist Name - Track Title
Note that the #EXTINF is metadata and can be used on a line above each file.