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Matchmaking Guide

Nancymon
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League of Legends uses a mathematical system to match up players of similar skill in the "Normal" and "Ranked" game types. The basic priorities of the system are (in respective order):

  1. Protect new players
  2. Create fair and competitive matches
  3. Make games less toxic by matching you with the right players

The system will extend queue times over sacrificing accuracy, which is why challenger players may face much longer queue times than the average player.

Each player is assigned a number that represents his skill level (MMR) which is determined by the outcomes of his previous games. With this matchmaking rating, the system will attempt to assemble two teams as fairly as possible to create a game wherein both teams have an equal chance of winning.



 

How does matchmaking work right now?

  • First, the system places players in the appropriate pool - which is basically the queue (normal, ranked, solo/duo, ranked 5-man team, etc.). Once in the pool, the system starts trying to find matches, with the goal of creating teams that are both made up of players with roughly equal skill and have a fair chance of winning.

Step 1: Determine strength:

  • If a player is queued alone, the strength is determined by his personal matchmaking rating (referred to as MMR from here on out) and number of wins for that particular queue. If the player is queued with a pre-made team, the system will adjust the MMR of the team accordingly. In most cases, we have found pre-made teams out-perform teams composed of unconnected players.

    Players have a separate MMR for each queue, each of which evolves independently from the others. This means that your wins and losses in Twisted Treeline won’t impact your MMR for Summoner’s Rift.

Step 2: Determine eligible opponents:

  • Initially, the system will only match players with similar MMR. As time passes, the system will very slowly broaden the MMR range it considers acceptable.

    New players get some special protection and are usually matched against other new players, though this may result in a longer delay before finding a game.

Step 3: Build a match:

  • Eventually, the system will assemble a group of players with comparable MMRs and put the players into a game.

 

 

Why don't you include other details, like how many kills or deaths I had, to determine my rating?

If we did, it would encourage players to focus on killing other players instead of strategically winning the game. For instance, players who choose supporting champions would be adversely affected because they are not expected to earn kills. By putting as many measurements and incentives as possible on specifically winning a game, we avoid side behaviors that aren't as fun and confuse the rating process.

 

 

Does the system use any information from the Leagues system when building matches for Ranked queues?

No. The system does not use your LP, progression status, tier, division, or any other piece of League information.

 

 

Why are dynamic groups allowed?

The new Champion Select allows players to play Ranked in a premade group with any number of other players. You can read more about our decision here.

 

 

How do I keep ending up in games with players whose skill level differs greatly from my own?

There are a few factors that can make a match feel more imbalanced than it actually is. A teammate may have just had a bad game and performed worse than they usually do. Alternatively, as we’ve seen in LCS, snowballing can still occur despite the two teams being very evenly matched. Snowballing can then lead to the very reasonable perception that a mismatch occurred. Finally, both the Dunning-Kruger effect and negativity bias also play a role here in shaping players’ impressions of their matchmaking experiences overall.

For the matchmaker itself, the conditions often cited for mismatch are low concurrent users (CCU) or having a very high MMR. But when we take a deeper look at this pool of games, the impact on the quality of matches ends up being very, very low. Instead, the matchmaker is much more likely to increase the queue time as can be seen in the longer queue times seen in the Challenger Tier.

That is not to say that our matchmaker is absolutely perfect. We are also constantly monitoring our matchmaker and making any necessary tweaks to help reduce the chance that players of vastly different skill levels are matched together.

 

 

But according to their ranked borders and third party website X, their MMR is way higher or lower than mine! Why does this happen?

There are two different issues to consider here. For borders, the main consideration is that they only represent the skill level of the player at the end of last season. This represents a skill evaluation that is rather old and very likely inaccurate when discussing current skill level. In terms of third party websites, their estimation of players’ MMR is based off of incomplete information and thus can be fairly inaccurate.

 

 

How is MMR determined for ranked teams?

When a team is first made, the past performances of the members in ranked solo queue will impact the starting MMR of the team. Once the team is established, the team's MMR exists independently from each of the member’s solo queue MMR.

 

 

Does "ELO Hell" exist?

Many players feel that, through no fault of their own, they are stuck in a situation where they can no longer progress. There are several key factors that can heavily contribute to this feeling. The first of these is that when we take a look across all games, some players actually require a pretty high number of games to reach their true MMR. For these players, what feels like an unsurpassable wall may end up being  just a small road bump.

From a psychological perspective, the two major factors which contribute to the sense of "ELO Hell" are the Dunning-Kruger Effect and negativity bias. The Dunning-Kruger effect refers to the phenomenon where people tend to rate their own abilities as much higher than average, regardless of reality. For League of Legends, this translates into most players rating their matchmaking rating at about 150 points higher than their actual matchmaking rating. Negativity bias refers to the cognitive trend where people’s negative experiences tend to be more mentally "sticky" than positive experiences. In other words, negative experiences, such as playing with a leaver or a troll, will have a larger impact on your memory.

There is no question that being human can leave us feeling frustrated with our peers. At the same time, when we have analyzed the problem mathematically, we have not yet found any statistical evidence of a win-rate bias. The bottom line is that our players care and therefore we care and will continue looking at the problems for ways to improve the experience.

 

 

How does Riot feel about smurfs?

Riot does not officially condemn or condone smurfing. We understand the cases where players make new accounts in order to help teach new players the game, but are working on newer systems to provide a similar experience in a more positive way.

 

 

Can I beat this system by leaving the game early?

No. Your MMR adjusts based upon the team’s result. If your team wins, you will gain points; if your team loses, you will lose points.  Whether you are in the game at the end is irrelevant to this outcome. You do, however, incur other penalties for leaving. This is because various other options (which we considered) to account for people leaving end up being exploitable or can otherwise cause undesirable effects on the system. For example, if we reduced the rating loss of your teammates if you leave, then you might leave to help them preserve their ratings. If we gave you a penalty even if they won, we would be "deflating" the entire system of ratings over time, causing new players to possibly run into professional players eventually.

 

 

Why don't we just put toxic players into a different queue?

This concept, also known as Prisoner’s Island, has been proposed multiple times and considered by the Player Behavior team. However, we ultimately determined that this model was not a good fit for League of Legends. Not only does it go against our goal of reforming toxic players, but it also feels extremely negative in the rare case someone is incorrectly sent there. Finally, since League of Legends is a free to play game, prisoners may opt to just abandon their account and transfer their toxicity to our newest players.


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