The rules of Go govern the play of the game of Go, a two-player board game. The rules have seen some variation over time and from place to place. This article discusses those sets of rules broadly similar to the ones currently in use in East Asia. Even among these, there is a degree of variation.
Notably, Chinese and Japanese rules differ in a number of aspects. The most significant of these are the scoring method, together with attendant differences in the manner of ending the game.
While differences between sets of rules may have moderate strategic consequences on occasion, they do not change the character of the game. The different sets of rules usually lead to the same game result,How to play Go, British Go Association so long as the players make minor adjustments near the end of the game. Differences in the rules are said to cause problems in perhaps one in every 10,000 games in competition.Interview with Zhu Baoxun, Ranka Online. "The differences are more significant theoretically than practically. During the last 100 years no professional or amateur tournament has ever been stopped because of the differences of rules. In practice, the differences will cause problems only in very rare situations, maybe once in 10,000 games." — Zhu Baoxun, deputy chief arbiter of the First World Mind Sports Games, October 12, 2008.
This article first presents a simple set of rules which are, except for wording, identical to those usually referred to as the Tromp–Taylor Rules,Comparison of Some Go Rules, British Go Association themselves close in most essential respects to the Chinese rules. These rules are then discussed at length, in a way that does not assume prior knowledge of Go on the part of the reader. The discussion is for the most part applicable to all sets of rules, with exceptions noted. Later sections of the article address major areas of variation in the rules of Go, and individual sets of rules.
Basic rules A set of rules suitable for beginners is presented here. The rules are studied more fully in below.
Two statements of the same basic rules, differing only in wording, are given here. The first is a concise one due to James Davies. The second is a formulation of the basic rules used for expository purposes in this article.
Except for terminology, the basic rules are identical to the Logical Rules first proposed in their current form in September 1996 by John Tromp and Bill Taylor.Super Ko, Robert JasiekCommentary on Tromp–Taylor Rules, Robert Jasiek They are also quite close to the Simplified Ing Rules of the European Go Federation, the only exception being the method of ending the game.
Concise statement These rules appear in "The Rules and Elements of Go" by James Davies.Elementary Rules of James Davies They assume familiarity with the equipment used to play Go, for which one may refer to below.
Notes: The words move and territory are used differently here than elsewhere in this article; play and area, respectively, are used instead. A clarification to rule 5 is added in parentheses. The board is empty at the onset of the game (unless players agree to place a handicap). Black makes the first move, after which White and Black alternate. A move consists of placing one stone of one's own color on an empty intersection on the board. A player may pass their turn at any time. A stone or solidly connected group of stones of one color is captured and removed from the board when all the intersections directly adjacent to it are occupied by the enemy. (Capture of the enemy takes precedence over self-capture.) If a stone or solidly connected group of stones of one color is enclosed and will eventually be captured, they are removed as captured at the end of the game. No stone may be played so as to recreate a former board position. Two consecutive passes end the game. A player's area consists of all the points the player has either occupied or surrounded. The player with more area wins.
These rules rely on common sense to make notions such as "connected group" and "surround" precise. What is here called a "solidly connected group of stones" is also called a chain.
Reference statement The basic rules are formulated here in a more detailed way to ease their presentation in below. (Each rule and definition links to a detailed explanation in that section.)
An optional rule prohibiting suicide is included as Rule 7A.
Players and equipment Rule 1.Official AGA Rules of Go, Rule 1: "The two sides [are] known as Black and White[...]" Players: Go is a game between two players, called Black and White. Rule 2.Official AGA Rules of Go, Rule 1: "Go is a game of strategy between two sides usually played on a 19x19 grid (the board)." Board: Go is played on a plain grid of 19 horizontal and 19 vertical lines, called a board. Definition. ("Intersection") A point on the board where a horizontal line meets a vertical line is called an intersection. Rule 3.Official AGA Rules of Go, Rule 1: "The two sides, known as Black and White, are each provided with an adequate supply of playing tokens, known as stones, of the appropriate color."Rules of Go, Section 1.2 "Lens-shaped black and white stones are used. The number of stones is preferably 180 of each color. " Stones: Go is played with playing tokens known as stones. Each player has at their disposal an adequate supply (usually 180) of stones of the same color.
Positions Rule 4.Tromp–Taylor rules of go: "Each point on the grid may be colored black, white or empty."Simplified Ing Rules of the EGF: "The position is the distribution of black, white, and no stones on all the unique intersections of the grid. For a play, this is given after all its removals." Positions: At any time in the game, each intersection on the board is in one and only one of the following three states: 1) empty; 2) occupied by a black stone; or 3) occupied by a white stone. A position consists of an indication of the state of each intersection. Definition. ("Adjacent") Two intersections are said to be adjacent if they are connected by a horizontal or vertical line with no other intersections between them. Note that intersections which are one away from each other diagonally, i.e., intersections that are connected by one horizontal and one vertical line, are not considered adjacent. Definition.Simplified Ing Rules of the EGF: "Stones of the same colour are connected if they are adjacent or if there is a chain of adjacent stones of their colour between them. Likewise, empty intersections are connected if they are adjacent or if there is a chain of adjacent empty intersections between them." ("Connected") In a given position, two placed stones of the same color (or two empty intersections) are said to be connected if it is possible to draw a path from one intersection to the other by passing through only adjacent intersections of the same state (empty, occupied by white, or occupied by black). Definition. ("Liberty") In a given position, a liberty of a placed stone is an empty intersection adjacent to that stone or adjacent to a stone which is connected to that stone.
Play Rule 5.Official AGA Rules of Go, Rule 1: "The board is initially vacant [...]" Initial position: At the beginning of the game, the board is empty. Rule 6.Official AGA Rules of Go, Rule 2: "The players alternate in moving, with Black playing first." Turns: Black moves first. The players alternate thereafter. Rule 7. Moving: When it is their turn, a player may either pass (by announcing "pass" and performing no action) or play. A play consists of the following steps (performed in the prescribed order): Step 1. (Playing a stone) Placing a stone of their color on an empty intersection (chosen subject to Rule 8 and, if it is in effect, to Optional Rule 7A). It can never be moved to another intersection after being played. Step 2. (Capture) Removing from the board any stones of their opponent's color that have no liberties. Step 3. (Self-capture) Removing from the board any stones of their own color that have no liberties. Optional Rule 7A.Official AGA Rules of Go, Rule 5: "It is illegal for a player to move so as to create a string of their own stones which is completely surrounded (without liberties) after any surrounded opposing stones are captured." Prohibition of suicide: A play is illegal if one or more stones of that player's color would be removed in Step 3 of that play. Rule 8.Simplified Ing Rules of the EGF: "A play may not recreate a previous position from the game." Prohibition of repetition: A play is illegal if it would have the effect (after all steps of the play have been completed) of creating a position that has occurred previously in the game.
End Rule 9.Elementary Rules of James Davies: "Two consecutive passes end the game." End: The game ends when both players have passed consecutively. The final position is the position on the board at the time the players pass consecutively. Definition.Official AGA Rules of Go, Rule 12: "Territory: Those empty points on the board which are entirely surrounded by live stones of a single color are considered the territory of the player of that color."Though the Simplified Ing Rules use the word "territory" differently, they describe what is here defined to be a player's territory as consisting of "the empty regions that are adjacent only to intersections with stones of a player's colour". The Commentary to the rules further specifies: "During scoring, an empty region does not provide any points if a) it is adjacent to at least one black intersection and adjacent to at least one white intersection or b) the whole board is empty." ("Territory") In the final position, an empty intersection is said to belong to a player's territory if all stones adjacent to it and to all empty intersections connected to it are of that player's color. Definition.Official AGA Rules of Go, Rule 12: "Area: All live stones of a player's color left on the board together with any points of territory surrounded by a player constitute that player's area." ("Area") In the final position, an intersection is said to belong to a player's area if either: 1) it belongs to that player's territory; or 2) it is occupied by a stone of that player's color. Definition.Simplified Ing Rules of the EGF: "The score of each player is the number of all intersections a) with stones of the player's color, and b) of the empty regions that are adjacent only to intersections with stones of the player's color." ("Score") A player's score is the number of intersections in their area in the final position. Rule 10.Simplified Ing Rules of the EGF: "For the final position, either the scores are unequal and the winner is the player with the greater score or the scores are equal and the game is a tie." Winner: If one player has a higher score than the other, then that player wins. Otherwise, the game is a draw.
Comparative features of the basic rules The essential features of these basic rules relative to other rulesets are summarized here. Each of the differences is discussed in greater detail in a later section of the article.
What variation exists among rulesets concerns primarily Rules 7A, 8, 9 and 10. The basic rules use area scoring, as in China and Taiwan, and as in the official rules of many Western countries. The main alternative is territory scoring. Though territory scoring is the system used in Japan and Korea, and is customarily used in the West, it is not possible to use territory scoring unless Rule 9 is replaced by a much more complex end-of-game rule. The goal of these basic rules is to present a simple system first. See below.