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Skill-based matchmaking
View on WikipediaSkill-based matchmaking (SBMM), also referred to as matchmaking ranking (MMR), is a form of matchmaking dependent on the relative skill level of the players involved.
History
[edit]A common rating system in chess is the Elo rating system, developed by Arpad Elo. Former International Chess Federation president Florencio Campomanes described it as an "inseparable partner to high-level chess".[1] In 2006, Microsoft researchers proposed a skill-based rating system using Bayesian inference and deployed it on the Xbox Live network, then one of the largest deployments of a Bayesian inference algorithm.[2] The researchers were displeased with the ranking system in the beta of Halo 2 (2004).[3] By the time Halo 2 launched, it was using TrueSkill.[4]
The term skill-based matchmaking first appeared in a 2008 interview with game designer John Carmack in which he emphasized its importance in Quake Live (2010). Upon setting up an account with id Software, the game will ask the player for their skill level and judge accordingly depending on their performance from that point forward.[5] The presence—or lack thereof—of skill-based matchmaking became a point of contention. During the development of Dota 2 (2013), Valve Software believed that the barrier to entry could be solved with, among other things, skill-based matchmaking through its Steamworks service;[6] when Call of Duty: Black Ops (2010) developer Treyarch was asked why the game wouldn't include skill-based matchmaking unlike Halo 3 (2007), multiplayer design director David Vonderhaar said that speed was "more important than anything else".[7]
Description
[edit]Team-based, competitive games such as League of Legends (2009), Counter-Strike: Global Offensive (2012), Dota 2 (2013), and Overwatch (2016) benefit from skill-based matchmaking. In contrast, Call of Duty: Black Ops II (2012)—a game that primarily focuses on single-player accomplishments—does not benefit from skill-based matchmaking.[8] Treyarch, who developed Call of Duty: Black Ops II, consciously queued players exclusively using ping and latency, in a subversion of industry standards at the time.[9]
Queues
[edit]In skill-based matchmaking, queue design focuses on how to divide parties into appropriate skill groups. In contrast to StarCraft II (2010), which focuses on player-on-player action, Blizzard Entertainment's Heroes of the Storm (2015) is a team-based game. The Heroes of the Storm matchmaker aims to have players win at least half of the games that they play. The game's matchmaker also aims to pair coordinated teams with other coordinated teams in order to avoid an unfair communication advantage.[10] According to game director Ben Brode, Hearthstone (2014) maintains a separate pool of new players. Players remain in the pool until they win ten games or obtain two legendary minions.
Player rating model
[edit]The skill rating of a player is their ability to win a match based on aggregate data. Various models have emerged to achieve this. Mark Glickman implemented skill volatility into the Glicko rating system.[11] In 2008, researchers at Microsoft extended TrueSkill for two-player games by describing a number for a player's ability to force draws.[12] Variability in map, character, and server effects have been considered in at least two research papers.[13][14] In 2016, two Cornell University graduates modeled skill rating as a vector of numbers, showing "substantial intransitivity".[15]
Reception
[edit]Skill-based matchmaking is a controversial practice. In Call of Duty: Warzone (2020), streamers of the game often seek out "bot lobbies"—lobbies with less-skilled players. The Washington Post compared the practice to "LeBron James looking to join pickup games at the local YMCA". Call of Duty: Warzone players who have spoken out against the game's use of skill-based matchmaking include 100 Thieves CEO Nadeshot, former professional Counter-Strike: Global Offensive player Shroud, and 100 Thieves co-owner CouRage. Competitive Call of Duty: Warzone player HusKerrs wrote that high-skilled players must "sweat or try hard" in order to create engaging content.[16] Streamer TimTheTatman refused to stream Call of Duty: Modern Warfare II (2022) upon discovering that it would implement skill-based matchmaking.[17]
In February 2023, Destiny 2 (2017) introduced skill-based matchmaking. Higher-skilled players subsequently discovered a way to enter lobbies with lower-skilled players, resulting in an outcry from the community.[18]
References
[edit]Citations
[edit]- ^ Elo 1986, p. x.
- ^ Herbrich, Minka & Graepel 2007, p. 7.
- ^ Perry, Douglass (October 28, 2005). "Live in the Next Generation: The TrueSkill System". IGN. Retrieved June 1, 2023.
- ^ Makedonski, Brett (October 31, 2014). "Master Chief Collection's multiplayer ranking system is just like Halo 2's". Destructoid. Retrieved June 1, 2023.
- ^ Chan, Norman (June 24, 2008). "Carmack frees Quake". GamesRadar+. Retrieved June 1, 2023.
- ^ Biessener, Adam (October 13, 2010). "Valve's New Game Announced, Detailed: Dota 2". Game Informer. Archived from the original on October 16, 2010. Retrieved June 1, 2023.
- ^ Grant, Christopher (September 3, 2010). "Call of Duty: Black Ops multiplayer takes aim at cheaters, looks to recruit more players". Engadget. Retrieved June 1, 2023.
- ^ Zook 2019, p. 36.
- ^ Petitte, Omri (October 26, 2012). "Call of Duty: Black Ops 2 uses ping and latency "exclusively" for multiplayer matchmaking". PC Gamer. Retrieved June 1, 2023.
- ^ Valenta, Nate (August 8, 2014). "Matchmaking Design in Heroes of the Storm". Blizzard Entertainment. Retrieved June 1, 2023.
- ^ Glickman 2001, p. 673-689.
- ^ Dangauthier et al. 2008, p. 931-938.
- ^ Menke, Reese & Martinez 2006, p. 1.
- ^ Chen et al. 2016, p. 1.
- ^ Chen & Joachims 2016, p. 1.
- ^ Davison, Ethan (May 27, 2022). "Video game developers want fair online games. Some players really don't". The Washington Post. Retrieved June 1, 2023.
- ^ Winslow, Levi (October 27, 2022). "Call Of Duty: Modern Warfare 2 Fans Can't Believe They Have To Play In Fair Matches". Kotaku. Retrieved June 1, 2023.
- ^ Kelly, Paul (February 15, 2023). "Destiny 2 PvP exploit sees skill-based matchmaking completely negated". PCGamesN. Retrieved June 1, 2023.
Works cited
[edit]- Chen, Shou; Joachims, Thorsten (2016). "Modeling Intransitivity in Matchup and Comparison Data" (PDF). Proceedings of the Ninth ACM International Conference on Web Search and Data Mining. pp. 227–236. doi:10.1145/2835776.2835787. ISBN 978-1-4503-3716-8. Retrieved June 1, 2023.
- Chen, Zhengxing; Sun, Yizhou; El-nasr, Magy; Nguyen, Truong-Huy (2016). "Player skill decomposition in multiplayer online battle arenas". Meaningful Play. arXiv:1702.06253. Retrieved June 1, 2023.
- Dangauthier, Pierre; Herbrich, Ralf; Minka, Tom; Graepel, Thore (January 2008). "TrueSkill Through Time: Revisiting the History of Chess" (PDF). Advances in Neural Information Processing Systems. Retrieved June 1, 2023.
- Elo, Arpad (1986). The Rating of Chess Players, Past and Present. Arco. ISBN 0-668-04721-6.
- Glickman, Mark (2001). "Dynamic paired comparison models with stochastic variances" (PDF). Journal of Applied Statistics. 28 (6): 673. Bibcode:2001JApSt..28..673G. doi:10.1080/02664760120059219. S2CID 16101322. Retrieved June 1, 2023.
- Herbrich, Ralf; Minka, Tom; Graepel, Thore (2007). "TrueSkill: A Bayesian Skill Rating System" (PDF). Advances in Neural Information Processing Systems. 20. Retrieved June 1, 2023.
- Menke, Joshua; Reese, Shane; Martinez, Tony (2006). "Hierarchical models for estimating individual ratings from group competitions". American Statistical Association. Retrieved June 1, 2023.
- Wallner, Günter, ed. (2019). Data Analytics Applications in Gaming and Entertainment. CRC Press. ISBN 9781000001860.
- Zook, Alex. "Chapter 3: Building Matchmaking Systems". In Wallner (2019).
Skill-based matchmaking
View on GrokipediaOverview
Definition
Skill-based matchmaking (SBMM) is a system employed in multiplayer video games to pair players with opponents or teammates of comparable estimated skill levels, thereby fostering balanced and competitive matches.[6] This approach relies on algorithmic evaluation of player performance to minimize disparities in match outcomes, promoting fairness by reducing the likelihood of one-sided encounters.[7] Unlike random matchmaking, which assigns players without regard to ability, SBMM prioritizes equity in competition over expediency or chance.[6] The core components of SBMM include input data derived from player statistics, such as win-loss records, kill-to-death ratios, and overall performance scores accumulated across sessions.[6] These metrics feed into a skill estimation process, typically involving rating systems that quantify a player's proficiency, though the precise methods vary by game and are often proprietary.[8] The output consists of assembled lobbies or teams where participants' estimated skills are closely aligned, aiming for an approximate 50% win probability for each side to enhance engagement. SBMM is commonly implemented in genres requiring precise coordination and competition, such as first-person shooters (e.g., Call of Duty), where balanced groupings help maintain challenge without overwhelming novices or underutilizing experts.[6] Skill rating systems, such as those akin to Elo, provide the foundational estimates but are referenced here only as enablers of the matching process.[8]Objectives
Skill-based matchmaking (SBMM) aims to promote fair competition by pairing players with opponents of similar skill levels, thereby creating balanced matches that minimize one-sided outcomes and enhance overall gameplay equity.[2] A core objective is to reduce player frustration from mismatched encounters, such as frequent losses against much stronger opponents, which can otherwise lead to disengagement.[2] By fostering environments where players can compete meaningfully, SBMM encourages skill improvement through challenging yet achievable interactions, allowing individuals to refine abilities without overwhelming discouragement.[8] Ultimately, these goals contribute to maintaining player retention, as balanced experiences keep a broader audience engaged over time.[2] Key principles guiding SBMM include targeting approximate 50% win rates for players to ensure consistent challenge without predictable dominance, achieved through algorithms that balance team compositions based on skill estimates.[8] This involves adaptive difficulty adjustments, where matchmaking constraints may loosen if wait times extend, prioritizing accessibility over perfect parity to avoid excessive queue delays.[2] Such principles support equitable participation across skill spectra, with 80-90% of players reporting improved match placements and reduced quit rates when skill is factored in.[2] On a broader scale, SBMM enhances accessibility for beginners by shielding them from elite players, while simultaneously providing experts with sufficiently competitive lobbies to sustain interest, thus broadening the game's appeal.[2] This sustained engagement indirectly bolsters monetization strategies, as retained players are more likely to invest in in-game purchases and long-term play.[9] A notable tension in SBMM design lies between upholding competitive integrity—through strict skill alignment—and preserving casual fun, where overly rigid matching can alienate relaxed players seeking low-pressure sessions.[2] Objectives often vary by game mode; for instance, ranked modes emphasize precise skill balancing to support progression and tournaments, whereas unranked modes adopt looser criteria to prioritize quick entry and social enjoyment.[2]Historical Development
Origins
The origins of skill-based matchmaking can be traced to the chess world, where the challenge of creating balanced tournament pairings necessitated a reliable method for assessing player strengths. In 1960, Arpad Elo, a Hungarian-American physicist, chess player, and professor, developed a rating system specifically designed to improve upon the existing Harkness method used by the United States Chess Federation (USCF).[10] This innovation provided a numerical value representing each player's relative skill as a probabilistic estimate derived from historical game outcomes, enabling organizers to pair competitors with similar ratings for more equitable matches.[11] The system's foundation in statistical modeling allowed it to predict expected results between players, adjusting ratings post-game to reflect actual performance and maintain accuracy over time.[12] The Elo rating system quickly proved its value and was formally adopted by the USCF in 1960, marking the first widespread implementation for chess tournament organization.[13] By 1970, the International Chess Federation (FIDE) had endorsed it as the global standard, applying it to international competitions and player classifications.[14] Arpad Elo personally oversaw rating calculations for FIDE until the mid-1980s, ensuring the system's reliability during its formative years.[10] This adoption underscored the system's role in promoting fair play, as equal-skill pairings minimized lopsided games and maximized competitive integrity. In the 1970s and 1980s, the Elo system extended into early computing applications beyond human tournaments, influencing simulations and board game evaluations. Computer chess programs, competing in events like the North American Computer Chess Championship starting in 1970, were assigned Elo ratings to gauge their performance against each other and human opponents, facilitating structured pairings in these nascent digital contests.[15] The 1990s brought a pivotal shift to fully networked digital platforms, adapting Elo ratings for real-time online matchmaking. The Internet Chess Server (ICS), established in 1992, was among the first to integrate the Elo system for player rankings, automatically pairing users based on their ratings during internet-based games.[16] This development transformed the analog rating concept into a cornerstone of virtual competition, enabling global access to skill-balanced play.Adoption in Video Games
Skill-based matchmaking in video games began to gain traction in the early 2000s, building on foundational rating systems like Elo, which originated in chess and influenced adaptations for online multiplayer environments. Microsoft introduced TrueSkill, a Bayesian skill rating system, in 2006 through its research division, deploying it for Xbox Live matchmaking to enhance player pairing beyond the simpler 1-50 ranking used in Halo 2 multiplayer. This marked an early milestone in integrating probabilistic models for more accurate skill assessment in console gaming. In 2008, id Software's John Carmack highlighted the importance of skill-based matchmaking during development discussions for Quake Live, emphasizing its role in pairing players of comparable ability to retain newcomers against seasoned competitors.[17] By the mid-2010s, adoption expanded across major titles leveraging online platforms. Riot Games implemented skill-based queues in League of Legends upon its 2009 launch, using a hidden matchmaking rating (MMR) derived from Elo principles to form balanced teams in normal and ranked modes.[18] Valve integrated SBMM into Dota 2 in 2013 via its Steamworks platform, introducing ranked matchmaking that required about 150 games to unlock and relied on MMR for equitable opponent selection in modes like All Pick and Captain's Mode.[19] Blizzard followed suit with Overwatch in 2016, launching Competitive Play in Season 2 that incorporated skill tiers and MMR-based matchmaking to group players by relative proficiency.[20] Key events underscored evolving priorities in implementation. Treyarch opted against full SBMM in Call of Duty: Black Ops (2010), focusing instead on connection quality to minimize queue times and prioritize accessible multiplayer sessions over strict skill balancing.[21] This approach shifted in Call of Duty: Black Ops II (2012), where Activision and Treyarch revamped matchmaking to emphasize ping and latency exclusively, moving away from region locks to ensure low-latency games while deprioritizing skill as the primary factor.[22] Recent developments through 2025 reflect ongoing experimentation and refinements. In Pokémon UNITE's Season 23 (late 2024), The Pokémon Company announced a shift away from traditional MMR-based matchmaking, transitioning to a system reliant solely on Master rank ratings starting in Season 24 to streamline high-level play and reduce wait times.[23] Valve revamped Deadlock's MMR system in December 2024, unifying matchmaking pools across normal and ranked modes while incorporating hero-specific strengths and weaknesses for more nuanced pairings.[24] In contrast, Epic Games introduced Fortnite OG's Expert Duos mode in 2024, deliberately excluding SBMM and bots to recreate the unstructured, high-stakes lobbies of early Fortnite seasons.[25]Technical Mechanisms
Skill Rating Systems
Skill rating systems form the foundational component of skill-based matchmaking by assigning numerical values to players' abilities, enabling fair opponent pairing. These systems update ratings based on game outcomes, incorporating factors such as win/loss results, opponent strength, and uncertainty to reflect skill more accurately over time. Primary models like Elo and Glicko provide straightforward mechanisms for individual player assessment, while advanced variants such as TrueSkill and the Cornell model extend capabilities to handle team dynamics, draws, and contextual intransitivities.[26][27][28] The Elo rating system, developed by Arpad Elo in the 1960s for chess, represents one of the earliest and most influential approaches. It operates on a logistic model where a player's rating adjusts after each game based on the actual outcome compared to the expected outcome against the opponent. The core update formula is: Here, and are the updated and prior ratings, is a constant factor determining adjustment sensitivity (typically 32 for beginners and lower for experts), is the actual score (1 for win, 0.5 for draw, 0 for loss), and is the expected score calculated as: where and are the ratings of the player and opponent, respectively. This system assumes binary or ternary outcomes and promotes convergence toward stable ratings through iterative updates, though it does not explicitly model uncertainty in new or infrequent players.[26] Building on Elo's limitations, the Glicko system, introduced by Mark Glickman in 1995, incorporates rating deviation (RD) to quantify uncertainty and volatility in skill estimates. RD starts high for new players (e.g., 350 points) and decreases with consistent performance, allowing conservative adjustments for those with limited data. The update process uses a Bayesian framework to revise both the rating and RD based on game results, opponents' ratings, and their deviations, making it more robust for sparse match histories. Glicko-2, an adaptation, introduces a per-player volatility parameter to model potential skill changes over time and extends handling of non-binary outcomes, such as multi-player scores.[26] TrueSkill, developed by Microsoft Research in 2006, advances rating through a fully Bayesian probabilistic model suitable for team-based games and draws. Each player is represented by a skill distribution with mean (average skill) and standard deviation (uncertainty), initialized at and for conservatism. After a match, posterior distributions are computed using approximate message passing in a factor graph, accounting for team performance and partial outcomes without requiring exact skill differences. This enables handling of multi-player scenarios and draws by modeling win probabilities via a Gaussian cumulative distribution function on skill differences. TrueSkill's design ensures scalability for online platforms like Xbox Live, emphasizing uncertainty reduction over time.[27] The Cornell model, proposed by researchers at Cornell University in 2016, addresses intransitivity in matchups by representing skill as a vector rather than a scalar, capturing context-specific strengths such as performance on particular maps or against certain playstyles. Using a Bradley-Terry-like framework extended to vectors, it learns pairwise preference relations from matchup data, allowing predictions of non-transitive outcomes (e.g., rock-paper-scissors dynamics in games). This vector approach models skill as a low-dimensional embedding, enabling more nuanced ratings that adapt to environmental factors without assuming total orderings.[28]Matching Algorithms
Skill-based matchmaking algorithms utilize player skill ratings, typically derived from systems like Elo or TrueSkill, to pair individuals or teams in online games. The core process begins with queue formation, where players entering a matchmaking queue are categorized by game mode, region, and availability. Algorithms then apply skill bucketing to group players within narrow rating ranges, such as ±50 points, to ensure competitive balance while minimizing wait times. For team-based games, balancing occurs by sorting queued players by skill and assigning them alternately to opposing teams, often using a greedy approach that adds each subsequent player to the team with the current lowest aggregate skill sum to prevent imbalances.[3] Beyond primary skill considerations, algorithms incorporate secondary factors to enhance match quality and player retention. Latency (ping) is frequently prioritized to avoid network disadvantages, with thresholds like under 100 ms enforced for pairings. Other elements, such as playstyle preferences or hardware capabilities, may influence selections in specialized systems, though skill remains dominant. Trade-offs between match fairness and wait times are managed dynamically; for instance, broader skill buckets expand during low population periods to reduce queues from minutes to seconds, as modeled by formulas estimating wait time based on online player count and bucket granularity.[3][29] Common algorithms include greedy matching, which iteratively pairs the highest-rated available player with a suitable opponent within a predefined skill gap, enabling rapid queue resolution suitable for high-volume games. For more optimized outcomes, linear programming techniques formulate matchmaking as a minimum weight perfect matching problem on a graph of player nodes, where edges represent predicted match quality (e.g., win probability or engagement risk), solved in polynomial time to maximize overall balance across multiple pairs. A simple pseudocode example for Elo-based greedy pairing in a 1v1 queue might proceed as follows:function greedyPairing(queue):
sort queue by Elo descending
matches = []
i = 0
while i < queue.length - 1:
player1 = queue[i]
for j = i+1 to queue.length:
player2 = queue[j]
if abs(player1.Elo - player2.Elo) <= threshold:
matches.add((player1, player2))
remove player1 and player2 from queue
break
i += 1
return matches
function greedyPairing(queue):
sort queue by Elo descending
matches = []
i = 0
while i < queue.length - 1:
player1 = queue[i]
for j = i+1 to queue.length:
player2 = queue[j]
if abs(player1.Elo - player2.Elo) <= threshold:
matches.add((player1, player2))
remove player1 and player2 from queue
break
i += 1
return matches
