Freedb

freedb is a database of compact disc track listings, where all the content is under the GNU General Public License. It was originally based on the now-proprietary CDDB (compact disc database). As of April 24, 2006, the database holds just under 2,000,000 CDs. To look up CD information over the Internet, a client program calculates a hash function from the CD table of contents and uses it as a disc ID to query the database. If the disc is in the database, the client is able to retrieve and display the artist, album title, tracklist and some additional information.