M3U is a computer file format for a multimedia playlist. One common use of the M3U file format is creating a single-entry playlist file pointing to a stream on the Internet. The created file provides easy access to that stream and is often used in downloads from a website, for emailing, and for listening to Internet radio.
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 their Winplay3 software, but numerous media players and software applications now support the format.
Careless handling of M3U playlists has been the cause of vulnerabilities in many music players such as VLC media player, iTunes, Winamp, and many others.
1. File 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 systems 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:
- a local pathname relative to the M3U file location; e.g. Heavysets.mp3
- an absolute local pathname ; e.g., C:\My Music\Heavysets.mp3
- a URL.
1.1. File format Extended M3U
The M3U file can also include comments, prefaced by the "#" character. In extended M3U, "#" also introduces extended M3U directives which are terminated by a colon ":" if they support parameters.
Apple used the extended M3U format as a base for their HTTP Live Streaming HLS which was standardized in 2007 by the IETF as RFC 8216. Therein, a master playlist references segment playlists which usually contain URLs for short parts of the media stream. Some tags only apply to the former type and some only to the latter type of playlist, but they all begin with #EXT-X-.
1.2. File format M3U8
The Unicode version of M3U is M3U8, which uses UTF-8-encoded characters. M3U8 files are the basis for the HTTP Live Streaming HLS format originally developed by Apple to stream video and radio to iOS devices, and which is now a popular format for Dynamic Adaptive Streaming over HTTP DASH in general.
The current proposal for the HLS playlist format uses UTF-8 exclusively and does not distinguish between the "m3u" and "m3u8" file name extensions.
2. Internet media types
The only Internet media type registered for M3U and M3U8 is application/vnd.apple.mpegurl, registered in 2009 and only referring to the playlist format as used in HLS applications.
The current proposal for the HLS playlist format acknowledges two media types which it treats as equivalent: application/vnd.apple.mpegurl and audio/mpegurl. Likewise, these are the two types recommended for HLS use by Microsoft.
For non-HLS applications, no media types were standardized or registered with the IANA, but a number of media types are nonetheless associated with the historical and ongoing use of the M3U and M3U8 formats for general playlists:
These types, plus application/vnd.apple.mpegurl and application/vnd.apple.mpegurl.audio, are supported for HLS applications by for example Microsofts Windows 10 and Internet Explorer 9, and LGs WebOS.
3. ExamplesExample 1
This is an example of an extended M3U file on the Windows platform. Sample.mp3 and Example.ogg are the media files. 123 and 321 are the lengths in seconds. A length of -1 or 0 may be used when the media file is a streaming file, as there is no actual, predefined length value. The value after the length is the title to be shown, which is generally the same as the location of the file which is on the second line. On the Mac OS X and Linux platforms, Unix paths are used.#EXTM3U #EXTINF:123, Sample artist - Sample title C:\Documents and Settings\I\My Music\Sample.mp3 #EXTINF:321,Example Artist - Example title C:\Documents and Settings\I\My Music\Greatest Hits\Example.ogg Example 2
This example shows how to create an m3u file linking to a specified directory. The m3u file should contain only one string: the path to the directory. After starting, the media player will play all contents of the directory:C:\Music Example 3
Here is another example, using relative format. The M3U file is placed in the same directory as the music, and directories must be preserved when moving the playlist to another device if subdirectories are used. This method is more flexible, as it does not rely on the file path staying the same.
This is the same file as above, saved as sample.m3u in C:\Documents and Settings\User\My Music\#EXTM3U #EXTINF:123, Sample artist - Sample title Sample.mp3 #EXTINF:321,Example Artist - Example title Greatest Hits\Example.ogg
This format in an M3U allows copying to another device for playback. All files and directories referred to must also be copied.Example 4
Here is a mixed example:Alternative\Band - Song.mp3 Classical\Other Band - New Song.mp3 Stuff.mp3 D:\More Music\Foo.mp3.\Other Music\Bar.mp3
- "Stuff" is in the same directory that the playlist is stored in.
- "Song" and "New Song" are in sub-directories of the directory that this playlist is stored in.
- "Mine" is an MP3 stored on a web server.
- "Listen" is a Shoutcast stream.
- Alternative and Classical are sub-directories of the directory that this playlist is stored in.
- "Foo" is in the specified Windows volume and directory, which may or may not be the same directory the playlist is in.
- "Bar" is in a different directory at the same level as the playlist directory. The double-dots reference the parent directory of the playlist directory, then into the sub-directory "Other Music" to reach "Bar".
References to other M3U playlists, for example, are generally not well-supported.AnotherPlayList.m3u Example 6
The following is an example of a M3U playlist file for "Jar of Flies" album by "Alice in Chains" that was created by Mp3tag with the following custom option settings:
- playlist filename format = "%artist%_%album%_00_Playlist.m3u"
- tag to filename conversion format = "%artist%_%album%_$num%track%,2_%title%"
- playlist extended info format = "%artist% - %title%"
The following tag editor software allows users to edit the ID3 tags in MP3 files, and has support for creating M3U files.Linux
- EasyTAG, puddletag.
- Mp3tag, puddletag.
Media playersMulti-platform Android
- Astro Player, Kodi, N7Player.
- QuickTime Player
- Nintendo Switch with the YouTube site-specific app
- Wii U with the Internet Browser or YouTube app
- New Nintendo 3DS including XL and 2DS XL variants with Internet Browser app
- foobar2000, JRiver Media Center, JuK, MediaMonkey, PotPlayer, Winamp, Windows Media Player, XMPlay
- simple text file listing the system path to each MP 3 and saving the file with an M3U extension. The m3u playlist support made it the first widely available
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