Which Guitar Hero game was the first to support downloadable content?

Guitar Hero II was the first Guitar Hero game to support downloadable content. The feature arrived with its Xbox 360 version, which connected to the Xbox Live Marketplace for additional songs.

The PlayStation 2 release launched in 2006, but downloadable content was not part of that version. The Xbox 360 edition followed in 2007 with extra tracks and downloadable song packs, including songs drawn from the original Guitar Hero. Packs commonly contained three songs, while some tracks were offered individually.

This is often confused with Guitar Hero III because that game made downloadable songs more prominent and also supported online multiplayer. Guitar Hero III expanded the practice, but Guitar Hero II introduced it within the series. The downloadable material was eventually removed from the Xbox Live Marketplace in 2014, although previously downloaded content could still be reinstalled.