TrueSkill Rating System

Overview

TrueSkill (Microsoft Research) models each player's skill as a Gaussian distribution N(μ, σ²) where μ is estimated skill and σ is uncertainty. Supports teams and multiplayer (not just 1v1). Conservative rating = μ - 3σ. Uncertainty decreases with more games. Uses Bayesian inference via message passing.

When to Use

Trigger conditions:

• Rating players in team-based or multiplayer (3+ participant) games
• Building matchmaking systems that balance match quality
• When you need uncertainty estimates alongside skill ratings

When NOT to use:

• For simple 1v1 ranking with no uncertainty (Elo is simpler)
• For non-competitive ranking (product ratings — use Wilson Score)

Algorithm