Matchmaking is a multiplayer system that provides players the ability to enter into a game with less effort. Individuals or teams search for a game, and are matched by the system with other similar players. Once an appropriate number of players is found, the match is made and the game can begin. Halo: Combat Evolved is the only Halo game that does not feature any Xbox LIVE support.
 Halo 2
In Halo 2, the matchmaking system was fairly simplistic and very user-friendly, though it does not have any form of custom games search system that is present in Halo: Custom Edition. There are two options available in the matchmaking system; the Quickmatch and Optimatch.
The Quickmatch option immediately put the player in any available match from the most recent matchmaking playlist the player selected. The player, however, did not have any control over the gametype. Optimatch, on the other hand, allowed the player to search their preferred gametypes from a playlist and enter any available match.
The matchmaking data from Halo 2 would be used to help develop TrueSkill, the skill-based ranking system used in future Halo titles and other video games.
 Optimatch Playlist
 Halo 3
In Halo 3, players can choose from two forms of matchmaking; ranked and social with each having different gametypes. In both playlists, players are awarded Experience Points (EXP) for winning a match. Should they lose, no EXP will be given. However, if the player quits the game during a match, one EXP will be deducted from their account. Unlike Halo 2, if a party has a high variability of skill levels in the current playlist, it will acknowledge it as a "mixed party" and will attempt to match with another party or several parties of a similar mix of ranks between the players.
Halo 3 is the first Halo game to use the TrueSkill ranking system in matchmaking.
 Halo Wars
Halo Wars matchmaking system matches players together based on their TrueSkill ranking system, similar to other Halo titles. Players earn ranks by increasing their unique overall score. By playing and completing online matches against other players, a player's score is increased. When certain milestones are reached, as a player's score passes a pre-determined amount, a new rank is assigned to the player.
 Halo: Reach
Halo: Reach redefines the matchmaking system by introducing the Arena matchmaking system while preserving the standard matchmaking system from Halo 3.Additionally, Firefight and Campaign now posess matchmaking capabilities. The game also utilizes the TrueSkill ranking system, like Halo 3 and Halo Wars.
The Arena matchmaking system focuses only on Slayer-related gametypes and is somewhat similar to Halo 2's Optimatch option where players are able to alter their matchmaking settings by their preferred gametypes and playlist. In the Arena, players need to get rated for 5 days to get placed in a skill Division (Onyx, Gold, Silver, Bronze and Iron), in a 3 month-long seasons. At the moment arena is all about wins and losses.  .
To qualify for ranking, players will have to play a certain number of games a day to gain a "Daily Ranking" which will be an average of a player's best games from the day. From thereon, players will need a certain number of "Daily Rankings" in order to get a divisional ranking and compete in a season. If a player needs to get a ranking on five days to get a ranking for a season, then the player will have to play a couple of games every day for five individual days. Players will be informed the minimum participation they need in the Arena for each season.
- ^ GiantBomb: Matchmaking (Video Game Concept)
- ^ a b c TrueSkill: Matchmaking Made Easy for Xbox Live
- ^ HaloWars.com: Halo Wars Matchmaking FAQ
- ^ Bungie.net: The Arena
- ^ a b ComputerAndVideoGames: Bungie details its Player Investment
- ^ Bungie.net: Bungie Weekly Update: 03.19.10
- ^ Bungie.net: Welcome to the Arena