Gomoku
Play Gomoku against three CPU levels or a friend on the same device. Use shape hints and undo to practise open threes, fours and double threats.
Gomoku
Play Gomoku against three CPU levels or a friend on the same device. Use shape hints and undo to practise open threes, fours and double threats.
About Gomoku
Same-device play on a 15 by 15 board
The game uses a 15 by 15 board. Black moves first, players place stones on empty intersections, and the first side to connect five horizontally, vertically, or diagonally wins. Two-player mode is local same-device play.
Live shapes and dead shapes
To judge whether a run of stones is worth anything, look at both ends. Three in a row with both ends open is a live three: block one side and the other is still there. Once one end is blocked the run has only one direction left and is worth far less, and a run blocked at both ends is worth nothing at all, which is exactly how the computer here scores it. Before placing a stone, count how many directions your run can still grow in rather than how many stones it already has.
Building a threat that cannot be blocked
A single threat is easy to answer: your opponent blocks it and the position is calm again. Games are decided by opening two threats at once, for example by playing the intersection of two live threes so that one blocking move can only cover one of them. When choosing where to play, prefer squares that take part in two directions at the same time, which usually means the crossing points of your existing stones rather than the far end of a line. With shape hints on, the board rings the stones of every open three and four and marks the points that complete or block them, so you can see both threats forming before you commit.
Casual local CPU opponent
The computer has three levels. Easy only takes a win or blocks a four and otherwise plays near the stones; Normal looks two moves ahead and blocks open threes; Strong scores every shape for both sides, searches four moves ahead and builds its own double threats, taking well under a second per move on a phone. The game runs entirely in your browser with undo and a shape-hint overlay, but it is not an online multiplayer room, a rating ladder, or an engine for official renju rules (no forbidden moves, overlines count as five).
FAQ
Common questions and answers about this topic.
How do you play Gomoku?
Players alternate placing black and white stones on the 15×15 board. The first to connect five stones in a row—horizontally, vertically, or diagonally—wins. Black moves first.
How strong is the computer?
There are three levels. Easy wins when it can and blocks a four, otherwise it plays a random point near the stones. Normal looks two moves ahead and blocks open threes. Strong scores every shape on the board (open fours, fours, open threes and so on, for both sides), looks four moves ahead with alpha-beta search and will build double threats itself; expect to lose to it until you start counting its threats too.
Can two people play on the same device?
Yes. Pick "Two players" as the opponent in the lobby; the computer stays out and the two of you take turns on the same screen. Black always moves first, so swap seats between games if you want it fair. Shape hints work for both sides, so turn them off if you don't want to show your opponent where to block.
Do I need to sign up or install anything?
No. Gomoku runs entirely in your browser—no account, no download, no tracking of your moves.
What counts as a draw?
If every cell on the board is filled and neither side has five in a row, the game ends in a draw.
Does Black have an advantage by moving first?
Yes. Under free-style rules with no forbidden moves, Gomoku has been proven to be a first-player win, which is why tournament rulesets add forbidden moves for Black or an opening swap. This tool uses free-style rules with no forbidden moves and is meant for casual play; to even things out, take turns going first, or let the more experienced player take White.
Does a line of six or more also win?
Yes. The tool only checks for five stones in a row, and any longer line already contains five, so it wins just the same. Some tournament rulesets treat an overline by Black as a forbidden move and a loss; this tool does not use that rule.
How do I beat the strong computer?
The strong level blocks any single threat, so you need two at once: a four plus an open three, or two open threes, created by one stone. Turn on shape hints and watch the red rings — build open twos in two directions that cross at an empty point, then play that point. It only searches four moves deep, so threats that take five or six quiet moves to set up are where it is weakest. Play Black when you can: moving first is a real advantage in free-style Gomoku.