Halo 2 was the first game in the Halo series to include online multiplayer on Xbox.
Released for the original Xbox in 2004, Halo 2 expanded the series beyond Halo: Combat Evolved’s local multiplayer and system-link options. Its online multiplayer operated through Xbox Live, allowing players to compete over the internet in organized matchmaking and playlists. This feature became one of the defining reasons many players connected the original Xbox to Microsoft’s online service.
Halo 2’s campaign also broadened the story by allowing players to control the Arbiter in addition to Master Chief. The game was developed by Bungie and published by Microsoft Game Studios, and it became one of the most influential console online shooters of its era.
Halo 3 continued and expanded the online model on Xbox 360, but it was not the first Halo title with online multiplayer. Halo: Combat Evolved supported multiplayer locally and through system link, not native Xbox Live matchmaking on the original console.