[Locked] Matchmaking and Ranking FAQ

Why am I seeing all these Champs in my match, I’m only Diamond?
This often happens early in the season when there are low-level Onyx players who show as Champ because the first players past 1600 will get Champ. So, these aren’t really “Champs” per se, just Onyx players who played more games early in the season, and Onyx mixing with Diamond is OK when pop requires it.

Ranking or CSR (Competitive Skill Rank)
How do ranks work?
The goal of the ranking system is to provide players with a Rank that represents their historical ability to win matches against like-skilled opponents. For example, a Diamond 3 player with Diamond 3 teammates should beat other Diamond 3 teams 50% of the time. If that same player wins more or less than 50% of the time given equal teammates vs. equal opponents, their rank should go up or down.

However, it’s usually nearly impossible to ensure perfectly similar teammates and opponents, so instead the ranking system relies on a skill system to do the math necessary to adjust match outcome expectations based on the skill of all of the players actually in the match, and how they were assigned to teams.


How do you do that?
We use TrueSkill2 to determine player skill (also called MMR or matchmaking rating), and then we use Elo’s rating system to compare a player’s current CSR to their MMR, their teammates’ MMRs, their opponents’ MMRs, and a given match’s outcome. This results in a probability that the player was expected to win a given match given their CSR and everyone else’s MMR.

If a player’s CSR is correct (close to their MMR), and they play like-skilled opponents with like-skilled teammates, they will tend to go up +15 on a win and down -15 on a loss. If it was an easy match, however, they will go up less (e.g. +10) and down more (e.g. -20). The amount a player goes up and down is determined by the probability a player with that CSR would have won that match. If a player wins a lot of matches, but they have a really high CSR and were expected to win them, the player’s CSR is already correct and does not need to go up. Likewise, if a player loses most of their matches, but they were against much better opponents, the player’s CSR is correct and should not go down.

Note: for players Onyx and up, it is +5/-5 for even matches, and can go down to +1/-9 for matches that are too easy.

Why do you use TrueSkill2?
We have compared TrueSkill2’s accuracy on millions and millions of players and matches to several competing skill systems (including classic TrueSkill) and found it to be significantly more accurate at predicting who will win matches. Because the goal of the ranking system is to be accurate at telling players their ability to win matches, we chose the most accurate system at predicting that.
Why not just show the MMR then instead of CSR?
MMR is how we predict a player WILL do. CSR is what they have actually done. We prefer players to show they deserve their MMR before awarding it immediately. This also makes CSR a smoother version of MMR. MMR itself tends to be volatile and can sometimes swing up and down quite a bit as a player swings in performance. CSR tends to keep it even keel with a player’s established performance.
Why am I getting only +1 for a win but -9 for a loss?
There are two main reasons this can happen. These apply to any player, though I will be using the amounts that an Onyx player goes up and down rather than sub-Onyx because it’s more common there:

Reason 1:
You are in a somewhat stacked team, so you tend to play a lot of easy matches, meaning you have a 90%+ chance of beating your opponents. In this case, in order to prove you deserve to go up in rank, you need to win more than 90% of the time.

If you are already at the correct rank and playing teams you beat 90% of the time, then, out of 10 matches, you will win 9 gaining a total of +9 points, and lose 1 (-9) ending up back where you started. This is because you are playing as predicted, so your Rank should not go up. To prove the system is wrong, you must win more than it already predicts against a given opponent. If you are playing opponents your CSR predicts you to go 9-1 against, you need to go 10-0 in order to prove you should move up.

If the system could find you even opponents at your Rank, and your Rank was correct, then you would win 50% of your matches and get +5 on a win and -5 on a loss. So out of 10 matches you would win 5 (+25) and lose 5 (-25) and also end up back where you started. In order to rank up in that case, you would have to win more than 5-5 out of 10, at least 6-4, to move up in Rank.

If you are in this situation, it will be slow going and there’s no easy way around it other than changing the matchmaker to just not give you easy matches. But then you would have super long wait times and overall probably rank up at around the same rate, but with just less actual play time.

One solution to this is to play solo instead. You will lose a lot more matches that way since it will probably be able to balance teams without you being in a stack, and you will have worse teammates, but your rank will move faster. It may float down a bit at first because players tend to play better than their actual skill while in a party. That’s the trade-off.

Reason 2:
This can also happen if your CSR is currently well above your MMR. You will be matchmade at your MMR which is lower than your CSR, giving you matches that LOOK easy to your CSR, even if they don’t FEEL easy to play. You will see -9/+1 just like in the above case while your CSR floats back down to your MMR OR your MMR goes up through improved performance over time.

For example, you have an Onyx CSR but your MMR has floated down to Diamond due to poor recent performance. To the Ranks it now looks like an Onyx player is playing Diamond opponents, so you get very little on a win, and lose more on a loss.

What causes my CSR to get above my MMR?
A few main ways:

• You have played significantly worse the last few matches. MMR can drop very quickly if the system sees evidence that you are playing worse than before.
• You have been playing with a stacked team that is able to win more than 90% of their matches because no fair opponents are around. This will result in your CSR slowly creeping up because the system is giving you +1 when it should probably give you closer to 0.
• You usually play in a party but are playing solo. The system naturally increases your Rank by however much being in a party helps in a given playlist. Your CSR then represents how you play in a party instead of solo, so when you switch back to solo it will float down to how you play solo.

Does CSR take my personal performance into account at all?
or
I carried my team and we lost, and I still lost a lot of CSR, why is that?
The CSR system itself does not currently consider anything about in-game performance. So, playing well in a match will not reflect in that match’s CSR update at all.

However, TrueSkill2 DOES see that better performance and your MMR goes up when this happens. You don’t benefit from it in that match itself but having a higher MMR results in matching harder opponents, which results in you getting more CSR when you beat them.

The reason why we don’t now change it to use TrueSkill2’s performance results after the match is because H5’s original data plumbing as well as UI don’t support it, and we aren’t currently updating H5 while Halo Infinite is in development.