Solver

What Is a Poker Solver?

A poker solver is software that computes GTO strategies by iterating through the branches of a game tree until it finds a Nash equilibrium. A solver determines the mathematically optimal play for every hand in a defined situation, producing a strategy that cannot be exploited. Solvers have transformed poker study from a game dominated by intuition and received wisdom into a discipline where the answer to "what is correct here?" can be looked up.

How Solvers Work

Solvers use an algorithm called counterfactual regret minimisation (CFR) to simulate the same spot between two theoretical players millions of times. Each player starts with an arbitrary strategy and adjusts it, iteration by iteration, to reduce the regret of not having taken the better action. After enough iterations the two strategies converge toward an equilibrium where neither side can improve by changing. The output is a set of mixed strategies: for each hand in each situation, how often to bet, check, call, raise, or fold, and at which size.

The inputs matter as much as the algorithm. You choose the starting ranges for both players, the stack depth, the board, and the available bet sizes. A solve with two bet sizes gives a different answer from a solve with five, and a solve with a wrong preflop range gives a wrong postflop answer. That is why pre-solved databases such as Solver+ are built from solved preflop ranges and a consistent sizing scheme, so the results are comparable across spots.

Reading Solver Output

Solver output comes in layers. At the top is the range-level frequency: on a given flop the raiser might bet 60% and check 40%. Beneath it is the hand-level mix: pocket aces might check 73% of the time on one board and bet 97% on another. Beneath that is the EV of each action for each hand. Two rules keep you from misreading it. First, at equilibrium every action a hand takes with non-zero frequency has the same EV, so the useful signal is the frequency, not the EV difference between mixed actions. Second, the top node of a flop is the out-of-position player's decision, so the raiser's c-bet strategy sits one level deeper, after the check.

What Solvers Cannot Do

• They assume perfect opponents. Real opponents have leaks the solver does not model. The solution is the baseline, not the exploit.
• They require simplified inputs. Bet sizes, ranges, and stack depths are chosen by whoever ran the solve.
• They solve one spot at a time. A solution applies to one board, one preflop history, and one stack depth. The patterns transfer; the numbers do not.
• They do not teach. A solver shows you what is correct. Working out why, and turning that into a rule you can use at the table, is the study.

Practical Example

Take a 100bb 6-max cash game where the cutoff opens and the big blind calls. On an A♥ K♦ 7♣ flop, Solver+ has the cutoff betting 81% of the time, mostly at a large size, with ace-king and ace-queen betting almost always and queens and jacks checking most of the time. On a T♥ 8♥ 5♣ flop with an under-the-gun raiser, the raiser checks 40% of the time and checks pocket aces more often than it bets them. Two boards, two completely different strategies, one method for finding them. GTO Poker Fundamentals walks through both hand by hand.

How to Study With a Solver

The productive way to use a solver is to study one spot type across many boards and look for the pattern, rather than loading random hands you lost. Compare five ace-high flops and five connected flops as the raiser, and the rule (bet big and often with a range advantage, check more when the caller's range connects) emerges on its own. Then test the rule in a trainer and review the hands you got wrong. How to use a poker solver lays out that routine step by step, and five common solver study mistakes covers the traps.

Study Solvers with ThinkGTO

Solver+ is a database of pre-solved GTO spots for every flop and runout in the common preflop situations, on your phone and with no desktop required. Postflop+ turns the same solutions into decisions you make and get graded on. For a longer guide, read How to Use a Poker Solver Effectively.