Napster is a set of three music-focused online services. It was founded as a pioneering peer-to-peer (P2P) file sharing Internet software that emphasized sharing digital audio files, typically audio songs, encoded in MP3 format. As the software became popular, the company ran into legal difficulties over copyright infringement. It ceased operations and was eventually acquired by Roxio. In its second incarnation, Napster became an online music store until it was acquired by Rhapsody from Best Buy on December 1, 2011.
Later, more decentralized projects followed Napster's P2P file-sharing example, such as Gnutella, Freenet, BearShare and Soulseek. Some services, like LimeWire, Scour, Kazaa, Grokster, Madster, and eDonkey2000, were also brought down or changed due to copyright issues.