The Mac version supported only Windows Media encoded media (up to version 9) enclosed in the ASF format, lacking support for all other formats such as MP4, MPEG, and Microsoft's own AVI format. On the user interface front, it did not prevent screensavers from running during playback, it did not support file drag-and-drop, nor did it support playlists. While Windows Media Player 9 had added support for some files that use the WMV9 codec (also known as the WMV3 codec by the FourCC), in other aspects it was seen as having degraded in features from previous versions.
