Matchmaking Rating



Matchmaking Rating, or MMR is a value that determines the skill level of each player. This value is used in matchmaking. Winning increases a player's MMR, while losing decreases it.

Players with the highest ratings are listed on the world Leaderboards.

Matchmaking
In general, players with similar MMRs will be matched with each other.

Four MMR values are tracked independently:


 * Solo rating (Normal games)
 * Party rating (Normal games)
 * Solo rating (Ranked games)
 * Party rating (Ranked games)

MMR for ranked matches require approximately 10 games to calibrate. Players who rank in the top 200 for solo ranked matchmaking will appear on the Leaderboards.


 * Bot games do not use MMR.

Uncertainty
Uncertainty is the standard deviation of a player's MMR.


 * Players with high uncertainty are more likely to be matched with players that differ more greatly in skill level, and vice versa.
 * New accounts with few games played have high uncertainty, while older accounts with many games played tend to have low uncertainty.
 * Since normal and ranked matchmaking are tracked separately, a player who has many normal games will still experience high uncertainty in ranked matchmaking if he or she has only played a few ranked games, and vice versa.
 * Higher uncertainty leads to larger MMR adjustments after each match, and lower uncertainty leads to smaller adjustments.
 * If game outcomes (win/loss and individual performance) repeatedly match the system's expectations, uncertainty will decrease until it reaches a floor.
 * Conversely, unexpected match outcomes will tend to cause an increase in uncertainty.

Party
In general, parties receive bonus MMR when searching for matches. This is meant to compensate for superior party coordination, as well as partying with highly skilled members.


 * Parties skill and experience values are counted as an aggregate, not individual for each player.
 * Parties will receive a higher adjusted MMR.
 * Parties with large differences between members' MMRs will receive a higher adjusted MMR.

Updating
MMR will not be changed if:


 * A non-partied member of your team early abandons a normal match.
 * Poor network conditions have been detected. A message must appear in game in order for this to apply.

MMR will be changed if:


 * Any member of your team late abandons.
 * Any member of your party abandons in any form.
 * You are playing a ranked match, regardless of any abandons.

Visibility
By default, MMR is hidden to other players. However, there are certain ways to view another player's ranked MMR. MMRs for unranked games are not visible.


 * Steam friends can sometimes see each other's MMR.
 * It is not known why some friends cannot view each other's MMR.
 * Players in the same Party. (confirm?)
 * Individual MMR for all players is displayed at the end of ranked matches.
 * Party MMR is hidden.

Other Information

 * MMR is the principal, but not the only factor used in matchmaking.
 * The system also takes into account Experience (number of games played), Player Performance, Gold Difference and various hidden variables.
 * The system does not directly try to achieve any particular win rate for players.
 * However, it does try to ensure that each team has a 50% chance of winning by matching players of similar skills against each other.
 * This means that, over time, win-loss ratios will naturally settle around 50/50 for all but the very best players.
 * The system does not examine individual win / loss streaks or try to end them.
 * Win rate and win count are not related to MMR, nor are they meaningful measures of player skill.

Trivia

 * According to Valve, player opinions of the MMR system is highly correlated with their recent win rate.