Go (Weiqi, Baduk)

Go rules

• The board is a grid of 9, 13 or 19 lines each way. Stones go on the points where the lines cross, not inside the squares, and the edge points count too.
• Black plays first, then the players take turns, placing one stone per turn on any empty point. Stones never move once placed.
• The empty points directly next to a stone, up, down, left and right, are its liberties. Stones of one color that touch along the lines form a chain and share their liberties.
• When your stone takes away the last liberty of an opposing chain, that whole chain is captured and comes off the board.
• You may not play a stone that would have no liberties, unless it captures something and so gains liberties. Playing into such a point is called suicide, and it is not allowed.
• You may not play a move that recreates any earlier position of the board. This is called positional superko. Its most common case is the ko: when a single stone is captured in a way that would let the other player capture straight back, they must play somewhere else first.
• Instead of placing a stone you may pass. When both players pass one after the other, play stops.
• The players then agree which stones are dead: stones that could not escape capture if play went on. Dead stones are removed, and the board is counted.
• If the players can’t agree, either can choose to keep playing and settle it on the board. If play then stops a second time, every stone still on the board counts as alive.

Scoring: area counting and komi

This page counts by area, as Chinese rules do. Your score is the number of your stones on the board plus the number of empty points surrounded only by your stones. An empty region that touches both colors belongs to nobody. Captured stones are not counted separately: taking them simply means more of the board is yours.

Moving first is an advantage, so White receives komi, extra points added to their total. Komi here is 7.5 points. The half point means a game can never be tied.

In a handicap game the weaker player takes Black and starts with 2 to 9 stones already on the star points, and White moves first. Komi then drops to half a point, and White gets one point for each handicap stone, as in Chinese rules.

Territory counting, used by Japanese and Korean rules, counts only the empty points you surround plus the stones you have captured, including dead stones. Because each player places about the same number of stones, the two methods almost always give the same winner, usually with the same margin or one point apart. The main practical difference: under area counting, filling a neutral point or playing inside your own territory costs nothing, so you never lose points by making sure.

How to play on this page

1. Open Setup and choose your opponent: the computer, or 2 players on one device. To play someone elsewhere, choose “Friend online” to make a link.
2. Pick the board size. Against the computer, pick Easy, Medium or Hard, and whether you play Black and move first or White and move second. You can also give Black handicap stones.
3. With a mouse, the stone shows where it will go before you click. On a touch screen, the first tap shows your stone with guide lines along its row and column, and a second tap on the same point places it. Tap anywhere else to move it. You can turn this off under “On the board”.
4. The last stone played has a small ring on it. The numbers next to each player show how many stones they have captured, and the middle shows White’s komi. Turn on move numbers to see the order of the game, and letters and numbers around the board name each point.
5. Press Pass when there is nothing useful left to play. When both players pass, play stops and the page marks the stones it thinks are dead with a cross, and shows each side’s area with small squares.
6. Tap any group to mark it dead or alive again. The count below the board updates as you go. Then press “Accept the count”, or “Keep playing” to settle a disagreement on the board.
7. Undo takes back your last move, together with the computer’s reply. Resign ends the game at once. Your settings, score and the game in progress are saved in this browser.

Tips for beginners

• Corners first, then sides, then the center. A corner is guarded by two edges, so it takes the fewest stones to surround.
• Count liberties. Before each move, check whether any of your chains is down to one or two liberties, and whether any of your opponent’s is.
• A group needs two eyes to live: two separate empty points inside it that the opponent can never fill. A group with only one eye can be captured.
• Connect when your stones are cut apart. Two weak groups are much harder to save than one strong one.
• Don’t chase every stone. Often it is better to make your own position solid and take the big empty area elsewhere.
• When your opponent places a stone next to yours, it usually reduces your liberties. Respond to the threat before playing somewhere new.
• At the end, close the borders between your area and your opponent’s, and fill the neutral points. Under area counting every stone you place there is a point.

About the computer opponent

The computer is our own program. It plays thousands of quick random games from the current position and leans towards the moves that win most often. It has no opening book and was not trained on recorded games.

Easy is meant for your first games on 9 by 9. It makes a loose move about a third of the time, but it never misses a capture or leaves a group in atari, so it is a steady partner while you learn to capture and make eyes. Medium answers within a second or so, Hard thinks for up to three seconds, and both play their best on 9 by 9.

On 13 by 13 and 19 by 19 the computer is honestly weak, even on Hard. It defends and captures well, but it does not understand large-scale strategy. That makes the big boards a friendly place to practise, but anyone who already knows the game should expect to beat it.

Frequently asked questions

Do I need to download anything or sign up?

No. The game runs in your browser on a computer, tablet or phone. There is nothing to install and no account to create.

Is this the same game as Weiqi and Baduk?

Yes. Go is the English name, from the Japanese. In Chinese the game is called Weiqi and in Korean Baduk. The rules are the same everywhere, apart from small differences in how the end of the game is counted.

Which board size should I start with?

Start on 9 by 9. Games are short, every move matters, and you meet captures, ko and living groups right away. Move to 13 by 13 once you are comfortable, and to the full 19 by 19 board when you want the whole game.

What is komi, and why does White get 7.5 points?

Komi makes up for Black moving first. 7.5 points is the usual figure for area counting, and the half point means the game cannot end in a tie.

What is the difference between area and territory scoring?

Area scoring, used here, counts your stones on the board plus the empty points you surround. Territory scoring counts the empty points you surround plus the stones you have captured. The winner is almost always the same. Under area scoring you lose nothing by playing inside your own area, so you can always make sure of a group without being punished for it.

What is ko, and why can’t I take back the stone straight away?

A ko is a shape where a single stone is captured and the capturing stone could be captured straight back, forever. A move that would repeat an earlier position is not allowed, so after a ko capture the other player must play elsewhere first. If they make a threat you must answer, they may then retake the ko.

How are dead stones decided at the end?

After both players pass, the page suggests which stones are dead, and you can tap any group to change it. Against the computer, the count is accepted when your marking matches the computer’s own view of the dead stones. If it doesn’t, play goes on so that the question is settled on the board: capture the stones you think are dead, because when play stops again every stone left counts as alive.

How do handicap stones work?

A weaker player can take Black with 2 to 9 stones already placed on the star points, up to 5 on the small board. White then moves first. Komi drops to half a point, and White gets one point back per handicap stone. Each handicap stone is worth roughly one rank of difference in strength.

How strong is the computer?

Easy suits complete beginners on 9 by 9. Medium and Hard are stronger and play their best on the small board, where they will make you work for a win if you are new to the game. On 19 by 19, even Hard is gentle: an experienced player will find it easy to beat.

Can I play against a friend?

Yes. Choose “2 players, one device” to take turns on one device, or “Friend online” to send a link. Online, both players mark the dead stones together and the game is counted once both accept.

Will my score be saved?

Yes. Your settings, your score and the game in progress are saved in this browser, so they will still be here when you come back. They are not sent anywhere, and clearing your browser data removes them.