--- title: "Opening book in chess" url: "https://georgelichess.com/glossary/opening-book.md" canonical_url: "https://georgelichess.com/glossary/opening-book" last_updated: "2026-11-07" type: "reference" summary: "An opening book is a database of opening moves and positions that an engine or program consults to play known theory quickly." related: ["https://georgelichess.com/glossary/opening.md", "https://georgelichess.com/glossary/opening-theory.md", "https://georgelichess.com/glossary/opening-repertoire.md", "https://georgelichess.com/glossary/opening-preparation.md", "https://georgelichess.com/glossary/opening-explorer.md", "https://georgelichess.com/glossary/chess-engine.md", "https://georgelichess.com/glossary/category/computer-chess.md", "https://georgelichess.com/glossary.md"] --- # Opening book 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. An opening book is a database of opening moves and positions that an engine or program consults to play known theory quickly. An opening book is a database of opening moves and positions that an engine or program consults to play known theory quickly, instead of calculating each early move from scratch. An [opening](https://georgelichess.com/glossary/opening.md) book stores the moves that strong players have chosen in the early stages of the game. A program that has a book can answer a known position immediately, saving time and avoiding weak early choices. Books are also used by human players in the sense of [repertoire](https://georgelichess.com/glossary/opening-repertoire.md) files, which hold the lines they plan to play. The usefulness of a book is that it reflects accumulated experience. Moves in the book have usually been tested in many games, so they are rarely poor. Some books include statistics on how often each move was played and how it scored, which helps you see what is popular and what is rare. For your own study, a book is a starting point, not a substitute for understanding. Memorizing long lines without knowing the plans behind them leaves you stranded as soon as the opponent leaves [theory](https://georgelichess.com/glossary/opening-theory.md). Learn the main ideas, the typical pawn structures and the usual middlegame plans of your openings, and use a book or [database](https://georgelichess.com/glossary/database.md) to check the details. Deviations from the book in your games are valuable moments to study afterwards. Also called: book. Also worth reading is [Opening explorer](https://georgelichess.com/glossary/opening-explorer.md). An opening explorer is a tool that shows, for any position reached from the start, which moves players have chosen in past games and how often each move led to a win, draw or loss. Compare it with [Endgame tablebase](https://georgelichess.com/glossary/endgame-tablebase.md). An endgame tablebase is a precomputed database that gives the exact result and best moves for every position with a small number of pieces, so engines can play those endgames perfectly. Computer terms such as "Opening book" are most useful next to a coach who reads your games with you, which is how a [first lesson](https://georgelichess.com/book/first-lesson.md) with George Li works. ## Related terms - [Opening](https://georgelichess.com/glossary/opening.md) - [Opening theory](https://georgelichess.com/glossary/opening-theory.md) - [Opening repertoire](https://georgelichess.com/glossary/opening-repertoire.md) - [Opening preparation](https://georgelichess.com/glossary/opening-preparation.md) - [Opening explorer](https://georgelichess.com/glossary/opening-explorer.md) - [Chess engine](https://georgelichess.com/glossary/chess-engine.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 - [Opening in chess](https://georgelichess.com/glossary/opening.md) - [Opening theory in chess](https://georgelichess.com/glossary/opening-theory.md) - [Opening repertoire in chess](https://georgelichess.com/glossary/opening-repertoire.md) - [Opening preparation in chess](https://georgelichess.com/glossary/opening-preparation.md) - [Opening explorer in chess](https://georgelichess.com/glossary/opening-explorer.md) - [Chess engine](https://georgelichess.com/glossary/chess-engine.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)