Play Go (Weiqi / Baduk) Online vs the Computer

Play Go — the ancient game also known as Weiqi in China and Baduk in Korea — directly against the computer, free, in your browser, with no download and no sign-up. Choose a 9×9, 13×13 or full 19×19 board; you play the black stones and move first, and the AI plays white. Click an intersection to place a stone: surround empty points to make territory, and surround an enemy group completely to capture it. The full rules are here — captures, liberties, the ko rule, illegal suicide, passing and automatic area (Chinese) scoring — with ghost-stone previews, a move hint, undo, live capture counts and win tracking per difficulty.

How the AI thinks

Go is famously hard for computers: a 19×19 board has hundreds of legal moves each turn and no simple way to score a position, so the game-tree search that powers our Chess and Othello engines does not work here. Instead this opponent uses Monte Carlo Tree Search: for each candidate move it plays out thousands of fast, random games to the end, keeps the moves that tend to win, and searches those lines more deeply — the same core idea behind the modern Go programs that first beat professionals, but running a lightweight random rollout rather than a trained neural network. The whole engine runs locally in your browser in a background worker thread, so nothing is sent to a server and the page stays responsive. It is an enjoyable, genuine opponent for casual and improving players and is at its strongest on the 9×9 board; on 13×13 and especially 19×19 it plays more loosely. We do not claim it plays at professional or top-bot strength.

How to play Go — the rules

• Place and connect. Players alternate placing a stone on any empty intersection; black goes first. Stones never move, but touching stones of the same colour form a group that lives or dies together.
• Liberties. The empty points directly next to a stone or group are its liberties. A group with at least one liberty stays on the board.
• Capture. When you place a stone that removes an enemy group's last liberty, that whole group is captured and lifted off the board. You may not play a stone that would leave your own group with no liberties (suicide) — unless the move captures.
• Ko. You cannot immediately recapture in a way that recreates the previous position; play elsewhere first. The game enforces this for you.
• Passing and the end. Either player may pass instead of playing. Two passes in a row end the game. Because scoring counts the board as it stands, capture any dead stones before you both pass.
• Scoring. Your area is your stones plus the empty points only your colour surrounds; white adds komi (7.5 here) to offset moving second. The larger area wins — the board is shaded so you can see the result.

Tips for beginners

• Start on 9×9. Same rules, far shorter games — you will meet capturing, life-and-death and territory many times per session, which is how the game clicks.
• Make two eyes. A group with two separate internal empty points (eyes) can never be captured. Living groups and killing the opponent's are the heart of Go.
• Corners, then sides, then centre. Territory is easiest to enclose in the corners, harder on the sides and hardest in the open centre — strong openings claim corners first.
• Don't cram. Stones work best with a little space between them; a wall of solid stones surrounds less territory than the same stones spread out.
• Stay connected, keep liberties. Groups low on liberties get captured — count them, and connect weak stones before they are surrounded.

FAQ

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