Play Weiqi vs Computer Free: Beat the Go AI on 9×9
October 2, 2026
Go — called weiqi in Chinese, baduk in Korean and igo in Japanese — has the simplest rules of any great board game and some of the deepest strategy. A 9×9 board is the ideal place to learn: a game takes about ten minutes, and nearly every lesson of the full 19×19 board shows up in miniature. This guide covers everything you need to beat our free Go vs Computer, from your first capture to the level-by-level tricks that win ranking points.
The rules in one minute
Black and White take turns placing one stone on an empty intersection, and Black plays first. Stones never move. Stones of one colour that touch along the lines form a group, and the empty points next to a group are its liberties. A group with no liberties left is captured and removed. You may not play a stone that would have no liberties, unless that move captures something. Either player may pass, and two passes in a row end the game.
How the game is scored
The game uses area scoring (Chinese rules): your score is your stones on the board plus the empty points surrounded only by your colour. White receives 6.5 points of komi for moving second, so ties are impossible — as Black you must lead on the board by at least 7 points. The counter scores the position exactly as it stands and never asks which stones are dead, and that matters more than anything else in this guide: an enemy stone left inside your area makes that empty region touch both colours, and the whole region then counts for nobody. Before you pass, capture every dead stone inside your territory. Under area scoring, playing inside your own territory costs you nothing, so take your time.
Liberties and capture
A lone stone in the middle has four liberties, on the edge three, and in the corner only two. A group down to one liberty is in atari — one move from capture. The best habit you can build is counting liberties before every fight: when two groups are squeezing each other, the one with fewer liberties dies first. Connect stones that are cut off and weak, and don’t keep running with a group in atari unless you can see it gaining liberties — that is how the biggest captures happen.
Eyes, life and death
An eye is an empty point surrounded by your stones. Your opponent cannot play there, because the stone would have no liberties, unless that move captures. So a group with two separate eyes can never be captured: it is alive. A group with only one eye, or none, will die once it is surrounded. On 9×9 the edges and corners help you make eyes cheaply. When one of your groups is attacked, making its second eye usually matters more than any number of points elsewhere; equally, the fastest way to kill an enemy group is to take the vital point that leaves it no room for two eyes.
Ko
Sometimes you capture a single stone and your opponent could immediately capture back, returning the board to the same position. The ko rule forbids that instant retake: the forbidden point is marked with a small red square and the ban lasts for one move. Play a forcing move somewhere else first — a ko threat — and if your opponent answers it, you may retake the ko.
A simple 9×9 opening
As Black, the centre point (tengen) and the third-line points near the corners are both strong first moves, and on Normal and Expert the computer itself always opens on the third line or higher, never on the edge. Next, claim a second corner or side on the third line, and keep your stones close enough to connect — one or two spaces apart. Stones on the first and second lines make too little territory, while stones floating far from their friends become targets. Once the board is divided, play the boundaries: moves that push into your opponent’s area while enlarging yours are the biggest on the board.
How the computer plays
Go is far too big for the brute-force search used by chess engines, so our computer mixes fast tactics with Monte-Carlo playouts. Before every move it plays hundreds of quick random games from the current position to estimate who will own each point, which borders are still open and which groups are already dead. It then scores the sensible moves: captures, rescuing its own stones from atari, putting your stones in atari or in a working ladder, and taking the most unsettled areas. It never fills its own eyes, never plays a self-atari that just loses stones, does not crawl along the first or second line in the opening, and does not waste moves inside its own secure territory. Easy is different on purpose: it uses only the quick tactical part, with plenty of randomness. The computer passes when no border, capture, dead stone or neutral point is left to play — or, after you pass, when the count as it stands already gives it the win. It runs entirely in your browser, so it also works offline.
Beating each level
- Easy (+10 points). About six moves in ten are chosen loosely from any reasonable-looking point; the rest are its best tactical move. Play solid shapes, capture the stones it leaves in atari, and simply surround more space than it does.
- Normal (+30 points). It plays the best move from its playout analysis every time, with a little variety. It captures anything you leave in atari, saves its own groups when it can and knows roughly where the territory is, so keep at least two liberties on every group and make your own groups safe before you attack. Its reading is short, though: life-and-death fights and capturing races are where you can outplay it.
- Expert (+100 points). It also tests its 10 most promising moves with over a hundred playouts each, gives the best three a few hundred more, and keeps the move with the best average final score — about 2,400 playouts every turn. It judges territory and weak groups far better than Normal, so take Black, open in the centre or on the third line, claim two corners early and keep your groups connected. Like every playout engine it can still misjudge tight life-and-death shapes and long capturing races, so count often and look for the fight it underestimates.
- Try 13×13 too. The levels and points are the same on the bigger board. The computer spends about the same thinking time there, so it reads each point less deeply — wide-open corners and big frameworks are your best chance.
Finishing the game without throwing it away
- When the computer passes, it is only saying it sees nothing useful — not that the game is over. Check the whole board before you pass back.
- Capture dead stones first. Any enemy stone left inside your area turns that whole empty region neutral at the count.
- Fill the neutral points. Under area scoring every empty point between the two sides is worth one point to whoever fills it.
- Then pass. Two passes end the game, the board is counted, and a win adds 10, 30 or 100 points to the leaderboard when you are signed in. Losses cost nothing.
Ready? Play Go vs Computer free in your browser — no download, and it works offline — or play Go with a friend on the same screen.