SHOUTcast is cross-platform proprietary software for streaming media over the Internet. The software, developed by Nullsoft (purchased by AOL on June 1, 1999), allows digital audio content, primarily in MP3 or HE-AAC format, to be broadcast to and from media player software, enabling the creation of Internet radio "stations". SHOUTcast Radio is a related website which provides a directory of SHOUTcast stations.
The SHOUTcast software uses a client-server model, with each component communicating via a network protocol that intermingles audio or video data with metadata such as song titles and the station name. It uses HTTP as a transport protocol. Although multicast was planned, it was never developed.
SHOUTcast servers and clients are available for FreeBSD, Linux, Mac OS X, Microsoft Windows, and Solaris. Client-only versions exist for Android, BlackBerry OS, iOS (iPad, iPhone), Palm OS and webOS (Radio Hibiki), PlayStation Portable, Windows Mobile, Symbian S60 and UIQ, Nintendo DS (DSOrganize), and Wii.
The output format is supported by multiple clients, including Nullsoft's own Winamp as well as Amarok, Exaile, foobar2000, iTunes, Songbird, Totem, XMMS, and Zinf. If the client does not support the SHOUTcast protocol, then the SHOUTcast server sends the stream without the metadata thus allowing it to be heard/viewed in clients like Windows Media Player. SHOUTcast servers are usually linked to by means of playlist files, which are small text files (usually with extensions .pls or .m3u) that contain the URL of the SHOUTcast server.
When that URL is visited in a Web browser which identifies itself as Mozilla-compatible (as most do), the server will return a generated SHOUTcast server info/status page, rather than streaming audio.