A playlist is a list of video or audio files that can be played back on a media player either sequentially or in a shuffled order. In its most general form, an audio playlist is simply a list of songs, but sometimes a loop. The term has several specialized meanings in the realms of television broadcasting, radio broadcasting and personal computers.
A playlist can also be a list of recorded titles on a digital video disk. On the Internet, a playlist can be a list of chapters in a movie serial; for example, Flash Gordon in the Planet Mongo is available on YouTube as a playlist of thirteen consecutive video chapters.
The term originally came about in the early days of top 40 radio formats when stations would devise (and, eventually, publish) a limited list of songs to be played. The term would go on to refer to the entire catalog of songs that a given radio station (of any format) would draw from. Additionally, the term was used to refer to an ordered list of songs played during a given time period. Playlists are often adjusted based on time of day, known as dayparting.
Cable TV and broadcast TV news channels often use video playlists to re-run pre-recorded news stories. A given news story might initially be shown live and then placed into a playlist to be shown over and over again at a later time. News channel broadcasting is a combination of live and pre-recorded programming. The pre-recorded clips are usually run from a playlist
As music storage and playback using personal computers became common, the term playlist was adopted by various media player software programs intended to organize and control music on a PC. Such playlists may be defined, stored, and selected to run either in sequence or, if a random playlist function is selected, in a random order. Playlists' uses include allowing a particular desired musical atmosphere to be created and maintained without constant user interaction, or to allow a variety of different styles of music be played, again without maintenance.
Several computer playlist formats for multimedia players, such as PLS, can pass a playlist or URL to the player. In the case of radio stations it can also link many audio players directly to the station's live streaming audio, bypassing any need for a web browser. (In that case the playlist file is typically downloaded from the station's live streaming web page, if offered. The files are similar to Internet shortcut files in appearance and internal structure, except used by media players rather than web browsers.)
Some Internet streaming services, such as Spotify, Amazon Music, 8tracks, and the defunct Playlist.com and Webjay, allow users to categorize, edit, and listen to playlists online. Other sites focus on playlist creation aided by personalized song recommendations, ratings, and reviews. On certain sites, users create and share annotated playlists, giving visitors the option to read contextual information or reviewer comments about each song while listening. Some sites only allow the sharing of the playlist data with the actual music being delivered by other channels, e.g., Plurn, others provide a closed catalog of content from which the playlists can be generated while sites like imeem allow users to upload the music to central servers to be shared and accessed by any user of the site. iPods can also be used to build playlists.
Pandora is another music streaming service that is available on the Internet. Pandora is one of the few music services that is free (no subscription required) to users. The user can select genres that are played back at random on Pandora's playlists.
On video hosting service websites such as YouTube and Vimeo, users can make playlists of select videos from themselves or other users for topical purposes; paid accounts can upgrade playlists of their own videos to "shows".
Most media players, such as Winamp, can easily create custom playlists from one's media library. For example, in a software MP3 player for Windows, Android, or macOS, the desired tunes are typically dragged and dropped from the user's music library into the player's "edit or create playlist" window and saved.
The idea of automatically generating music playlists from annotated databases was pioneered by François Pachet and Pierre Roy. Constraint satisfaction techniques were developed to create playlists that satisfy arbitrary "sequence constraints", such as continuity, diversity, similarity, etc. Since, many other techniques were proposed, such as case-based reasoning.
Notable file formats used for playlists include: