.hack//Roots is a 26-episode anime series, animated by studio Bee Train, that sets as a prologue for the .hack//G.U. video games. It is the first .hack TV series broadcast in HDTV (1080i). It is set seven years after the events of the first two anime series and games. .hack//Roots revolves around an MMORPG game called The World R:2, also known as The World Revision:2 and serves a sequel to the original version of "The World".

.hack//G.U. is a series of single-player action role-playing games for the PlayStation 2, developed by CyberConnect2 and published by Bandai Namco Entertainment between 2006 and 2007. The series contains three games: .hack//G.U. Vol. 1//Rebirth, .hack//G.U. Vol. 2//Reminisce and .hack//G.U. Vol. 3//Redemption. As in the previous .hack games, .hack//G.U. simulates a massively multiplayer online role-playing game (MMORPG) called The World—the player controls a character who plays the fictional online game. They were directed by Hiroshi Matsuyama who aimed to address criticisms of the previous series. Its narrative, by Tatsuya Hamazaki, was written concurrently with .hack//Roots, an anime set before the events of the games.