M3USync is using the M3U (Moving Picture Experts Group Audio Layer 3 Uniform Resource Locator) file to locate your music files (mp3, wma, ...) on your hard disk. The M3U is a file format that stores multimedia playlists. It was originally implemented in Winamp, although it is now supported by many applications, including VLC media player, RealPlayer, Windows Media Player, iTunes and QuickTime Player.

An M3U file is a plain text file that contains the locations of the media files that the mediaplayer should play. Each location is placed on a new line. The locations can be either absolute or relative local pathnames (e.g., "C:\My Music\Song.mp3" or "Song.mp3") or they can be URLs. For keeping your music files movable, it is recommended to work with relative pathnames and save your playlists in your music folder.

To create and manage your M3U playlist you can use Winamp or other media player. You can also use a dedicated M3U Editors, several of them are available as freeware.

Once you have created your playlists you can add them to the M3USync synchronization list by clicking on the "Add" button or you can directly drag them in the list box. Several playlists can be specified and the last synchronization list is automatically restored when the program is restarted.