Go · Rules & strategy

Board, stones and liberties

The full-size board has 19×19 lines (361 points); here you can also pick a quick 9×9 or a medium 13×13 board. Stones go on the intersections and never move once placed unless they are captured. The empty points directly next to a stone (up, down, left, right) are its liberties. Stones of one colour joined along the lines form a group and share their liberties; diagonal contact does not connect.

Capturing and atari

Fill the last liberty of an enemy group and the whole group is removed from the board. A group with only one liberty left is in atari: its owner must run, connect or find something bigger elsewhere. The number of stones each side has captured is shown at the top of the board.

No suicide, and the ko rule

You may not play a stone that leaves your own group with no liberties (suicide) — unless the move captures enemy stones and so gains liberties. When two single stones could capture each other back and forth, the shape is a ko. Retaking immediately would repeat the position, so it is forbidden: play a threat elsewhere first and retake after your opponent answers. This site remembers the last eight positions, which also stops short cycles such as triple ko. A forbidden ko point is marked with a red ×.

Ending the game and dead stones

When there is nothing useful left to play, press Pass. Two passes in a row start the counting phase: the computer marks stones it judges dead (shown semi-transparent). If a mark is wrong, tap the stone to toggle its whole group. When both players press Accept the result is final. If you cannot agree, choose Resume and settle the question on the board.

Area scoring versus territory scoring

This game uses area scoring (Chinese rules): your score is your living stones on the board plus the empty points surrounded only by your stones. Dead stones are removed and become the opponent’s territory; neutral points touching both colours (dame) belong to nobody. Japanese and Korean rules use territory scoring — empty points plus prisoners — but the winner is almost always the same and the margin differs by at most a point. Area scoring needs no prisoner bookkeeping, and filling the last neutral point is worth one point, so the end of the game is clear-cut.

Komi

Moving first is an advantage, so White receives komi. The default 7.5 is the standard for area scoring; 6.5 is the long-time Japanese and Korean tournament value; 0.5 leaves Black the full first-move edge and only rules out ties — handy when a weaker player takes Black. Thanks to the half point a game can never end in a draw.

Life and death: two eyes

A group completely surrounded by the enemy still lives for ever if it has two separate internal empty points — two eyes — because the opponent cannot fill both at once. With only one eye it will eventually be captured. Eye spaces of three points (straight or bent three) have a single vital point in the middle: take it to make two eyes for yourself, or take it first to kill your opponent’s group. Beware the false eye — a point that looks like an eye but whose diagonal is cut.

Opening: corners, then sides, then centre

A Chinese proverb says “gold corners, silver sides, grass belly”. Corners need the fewest stones to enclose territory, sides come next and the centre the most. On 19×19, start by taking corner points on the third and fourth lines (the 4-4 star point, the 3-4 point), then extend along the sides; the third line favours territory and the fourth favours influence. On 9×9 the fight begins at once, so central points such as tengen or the 3-3 and 3-4 points work well.

Ladders and nets

A ladder is a chase in which a stone in atari runs diagonally across the board in a staircase until it hits the edge and dies. If one of the runner’s stones already sits on that diagonal path (a ladder breaker), the ladder fails — so read it all the way before you start. A net (geta) blocks the escape route loosely from a distance instead of giving atari directly, and often works when the ladder does not.

Practical tips and the AI levels

Avoid leaving several weak groups at once; attack your opponent’s weak stones and build territory while you do it. In the endgame play the largest moves first — and under area scoring the last dame is still worth a point. The Easy AI thinks briefly and wobbles on purpose, Normal is a fair opponent for beginners on 9×9, and Hard reads more deeply and rarely misses a blunder. On 19×19 the AI plays quickly but reads shallowly, so win with the big picture.

FAQ