Windows Media Player Playlist (.wpl) files are client-side playlists that are written in a proprietary format. Microsoft introduced this file format in Windows Media Player 9 Series. The .wpl format can create dynamic playlists, whereas .asx and .m3u formats cannot. In Windows Media Player 9 Series, the auto playlist feature uses the .wpl format. The .wpl format is the default file format used for playlists that you save in Windows Media Player 9 Series.