Matchmaking Rating, or MMR is a value that measures the skill level of a player. This value is used in matchmaking; players with similar MMRs will be matched with each other. Winning increases a player's MMR, while losing decreases it.
All players have four hidden rankings values used to determine which opponents they will be match with.
Used for Practice and Quick Play matches, this behind the scenes rating is used to help find players of a similar skill. Although, due to the more casual nature of Quick Play, in these playlists we will first attempt to find players of similar MMR whom are queuing into the same datacenters as you, although to improve match making times, the acceptable skill range increases greatly overtime, and will eventually select any queued players if none of similar skill can be found in a timely manner.
In Practice, the average MMR of the human team will be used to determine the skill difficulty of the Bots.
Used in all Quick Play
Ranked MMR skill searches attempt to locate players of a similar skill, and refrains from searching beyond an acceptable range. Therefore, players may experience extended matchmaking times in ranked modes in comparison to Quick Play, but at the benefit of a more accurate skill match.
Used exclusively for Ranked Duel.
Used exclusively for Ranked 2v2 TDM. When two players party together, the highest MMR of the two partied players is used to find their opponents, not their average MMR.
Qualifiers and Rating Volatility
To assist in identifying an accurate MMR, new players may initially experience greater mobility, greatly increasing in rank by winning and decreasing in rank by losing. As players continue to play and we gain higher confidence in the accuracy of their rating, their rating will move at a slower rate, requiring a larger number of games to greatly impact their MMR. It is also possible to gain rank by losing to player with a higher skill rank if you out performed expectations and to lose rank by narrowly beating somebody with a significantly lower skill rank.
MMR for ranked matches require approximately 10 games to calibrate, before they are assigned a public Skill Rating.