Files with the .M3U extension are text files containing a playlist of audio or video files, namely a list of files and their locations. It does not contain the file data itself, which is to say music or movies.

The extension name stems from the MP3 URL abbreviation, which stands for Moving Picture Experts Group Audio Layer 3 – Uniform Resource Locator. M3U playlist files are used by media players such as Winamp or iTunes, usually for playing music – they are quite a universal format.