Game Tree

What Is a Game Tree?

A game tree is a branching diagram that maps every possible action, reaction, and outcome in a poker hand. Starting from the current decision point, each branch represents a possible action (bet, call, raise, fold, check), and each node represents a new decision point with its own set of branches. The game tree captures the complete strategic landscape of a hand.

How Game Trees Represent Poker

Consider a simplified river scenario where you can either bet or check, and your opponent can call, raise, or fold. Even this simple situation creates a tree with multiple branches. Now extend this to an entire hand — preflop actions, flop decisions, turn decisions, and river decisions — with multiple bet sizes at each node. The game tree explodes into millions or billions of decision points, which is why computing GTO strategies requires powerful Solver software.

Anatomy of a Game Tree

• Root node: The starting point of the hand or scenario being analyzed
• Decision nodes: Points where a player chooses an action (bet, check, call, raise, fold)
• Chance nodes: Points where a random card is dealt (flop, turn, river)
• Terminal nodes: Endpoints where the hand resolves through showdown or a fold

Practical Example: Simplified River Game Tree

You are heads-up on the river with $100 in the pot. You can check or bet $75. If you bet, your opponent can call or fold. If you check, your opponent can bet $75 or check back. This creates a tree with four terminal outcomes: you bet and get called (showdown), you bet and opponent folds (you win), you check and opponent bets (a new decision), or both check (showdown).

Why Game Trees Matter for Your Strategy

Understanding game trees helps you appreciate why certain strategies emerge from solver analysis. Solvers work by traversing the entire game tree, computing the optimal strategy at every node simultaneously. The solutions you see in Solver+ are the result of this exhaustive process. By exploring different branches of the game tree, you can understand why a solver recommends a particular action and how alternative lines compare. For practical guidance on interpreting solver output, read How to Use a Poker Solver Effectively.