MusicBrainz is a project which aims to create a collaborative music metadata database. MusicBrainz was founded in response to the restrictions placed on the Compact Disc Database (CDDB), a database for software applications to look up audio CD information on the Internet. MusicBrainz has expanded its goals to reach beyond a CD metadata (this is information about the performers, artists, songwriters, etc.) storehouse to become a structured online database for music. MusicBrainz captures information about artists, their recorded works, and the relationships between them. Recorded works entries capture at a minimum the album title, track titles, and the length of each track. These entries are maintained by volunteer editors who follow community written style guidelines. Recorded works can also store information about the release date and country, the CD ID, cover art, acoustic fingerprint, free-form annotation text and other metadata. As of September 2020, MusicBrainz contained information on roughly 1.7 million artists, 2.6 million releases, and 23 million recordings. End-users can use software that communicates with MusicBrainz to add metadata tags to their digital media files, such as ALAC, FLAC, MP3, Ogg Vorbis or AAC.