--- title: "Alpha-beta pruning in chess" url: "https://georgelichess.com/glossary/alpha-beta-pruning.md" canonical_url: "https://georgelichess.com/glossary/alpha-beta-pruning" last_updated: "2026-11-07" type: "reference" summary: "Alpha-beta pruning is a search technique that skips branches of the move tree that cannot change the minimax result." related: ["https://georgelichess.com/glossary/minimax.md", "https://georgelichess.com/glossary/search-depth.md", "https://georgelichess.com/glossary/chess-engine.md", "https://georgelichess.com/glossary/stockfish.md", "https://georgelichess.com/glossary/evaluation.md", "https://georgelichess.com/glossary/principal-variation.md", "https://georgelichess.com/glossary/category/computer-chess.md", "https://georgelichess.com/glossary.md"] --- # Alpha-beta pruning in chess > **For AI agents:** the complete index of GeorgeLiChess pages is [llms.txt](https://georgelichess.com/llms.txt). Every page is also served as markdown at its URL plus .md. Alpha-beta pruning is a search technique that skips branches of the move tree that cannot change the minimax result. Alpha-beta pruning is a search technique that skips branches of the move tree that cannot change the minimax result, letting engines look much deeper using the same amount of computing time. A [chess engine](https://georgelichess.com/glossary/chess-engine.md) must examine a huge tree of possible moves. Alpha-beta pruning is a method that cuts away parts of that tree without changing the answer. While searching, the engine keeps two bounds: the best score the side to move can already guarantee, and the best score the opponent can already guarantee. If a line is shown to be worse than an option already available, the remaining moves in that line need not be examined, because a sensible opponent would never allow it. The pruning gives exactly the same result as a full [minimax search](https://georgelichess.com/glossary/minimax.md), only far faster. Its power depends on looking at promising moves first, so engines order moves carefully, trying [captures](https://georgelichess.com/glossary/capture.md) and previous [best moves](https://georgelichess.com/glossary/best-move.md) before quiet ones. Good ordering lets the search go roughly twice as deep in the same time. You do not need to run this by hand, but it is a useful picture of how good players think too. When you find that one reply refutes a [candidate move](https://georgelichess.com/glossary/candidate-moves.md), you stop analyzing that move and turn to another. That habit of discarding a line once it is refuted saves time and keeps your [calculation](https://georgelichess.com/glossary/calculation.md) focused. Also called: alpha beta search. A neighboring idea is [Search depth](https://georgelichess.com/glossary/search-depth.md). Search depth is how many moves ahead an engine has looked in a position, counted in half-moves called plies, and deeper searches generally give more reliable evaluations and moves. A neighboring idea is [Stockfish](https://georgelichess.com/glossary/stockfish.md). Stockfish is a free, open-source chess engine developed by a worldwide community, widely regarded as one of the strongest engines available and used by many analysis websites and apps. An engine can tell you what "Alpha-beta pruning" means for a position, but not which mistakes you keep making; a [first lesson](https://georgelichess.com/book/first-lesson.md) with George Li reviews your games and finds those. ## Related terms - [Minimax](https://georgelichess.com/glossary/minimax.md) - [Search depth](https://georgelichess.com/glossary/search-depth.md) - [Chess engine](https://georgelichess.com/glossary/chess-engine.md) - [Stockfish](https://georgelichess.com/glossary/stockfish.md) - [Evaluation](https://georgelichess.com/glossary/evaluation.md) - [Principal variation](https://georgelichess.com/glossary/principal-variation.md) ## Guides that go further - [How to choose a chess coach](https://georgelichess.com/how-to-choose-a-chess-coach.md): What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid. - [How much does chess coaching cost?](https://georgelichess.com/chess-coaching-cost.md): Published rates for private, group and subscription chess coaching, with the source and the date of each. - [The first lesson](https://georgelichess.com/book/first-lesson.md): A game review, a read on your level and a written study plan from George Li. [Book your first lesson](https://georgelichess.com/book.md) and George Li reviews your games and builds a study plan around them. Questions about lessons: write to hello@georgelichess.com. ## Related - [Minimax in chess](https://georgelichess.com/glossary/minimax.md) - [Search depth in chess](https://georgelichess.com/glossary/search-depth.md) - [Chess engine](https://georgelichess.com/glossary/chess-engine.md) - [Stockfish in chess](https://georgelichess.com/glossary/stockfish.md) - [Evaluation in chess](https://georgelichess.com/glossary/evaluation.md) - [Principal variation in chess](https://georgelichess.com/glossary/principal-variation.md) - [Chess terms: Computer chess and analysis](https://georgelichess.com/glossary/category/computer-chess.md) - [Chess terms glossary: plain definitions](https://georgelichess.com/glossary.md)