M3U files are simply text files with a .m3u extension instead of a .txt extension. When opened in a browser from clicking on a link to an m3u file, the listener’s default audio program will launch the playlist. Many mp3 players support the m3u format, including Winamp and iTunes.

Here are the contents of an example M3U file:
#EXTM3U
#EXTINF:210,Song Title
mp3/song_title.mp3
#EXTINF:123,Song Title 2
mp3/song_title2.mp3

For each additional song in the playlist, you must add “#EXTINF:” followed by the length of the song in seconds, and the song title. The next line should be the path to the media. This can either be relative to the location of the mp3 file (e.g. mp3/song_title.mp3) or absolute (e.g. http://www.your-site.com/mp3/song_title.mp3)  Read more... (216 words, estimated 52 secs reading time)