MMR stands for "matchmaking rating." It is a hidden number that represents your skill. The game uses it to find opponents. A high MMR means you face strong players. A low MMR means you face beginners. The number goes up when you win. It goes down when you lose. It is the engine of competitive matchmaking.

MMR is different from rank. Rank is visible. MMR is hidden. You can be a gold rank with a high MMR. You can be a diamond rank with a low MMR. The system is complex. It tries to create fair matches. It does not always succeed. Smurfs and boosters distort it. The number is a best guess.

Related terms

• ELO: a similar rating system.
• Rank: the visible tier.
• Smurf: a high-skill player on a new account.
• Placement matches: games that set your initial MMR.

MMR is a shadow. It follows you. It decides who you play. It decides how fast you climb. It is invisible. It is also inescapable. Players obsess over it. They check third-party sites. They try to game it. The number is a mystery. The game knows. You do not.