Players take turns placing one stone on an empty intersection; Black goes first. The first to make an unbroken line of five stones horizontally, vertically or diagonally wins. Pick a rule set above: Free-style allows any line of five or more, Standard counts exactly five, and Renju balances Black's first-move advantage with forbidden moves, shown as red crosses. On a phone, “Tap twice to place” lets you check the preview stone before committing. Use the arrow keys and Enter to play from a keyboard.
Why the rules come in several versions
In plain five-in-a-row the player who moves first has a large advantage, and with perfect play on a 15×15 board Black can always force a win. That result was established by computer search in the 1990s, and it is the reason serious play rarely uses the free-style rules. Every other rule set on this page is an attempt to take some of that advantage away from Black.
Standard rules only count exactly five, so a line of six does not win. No double-three, the version most often played casually in Korea, forbids Black from creating two open threes with one stone. Renju goes further: Black may not make a double-three, a double-four or an overline, while White has no restrictions at all and may even win by forcing Black into a forbidden point.
Threes and fours: the shapes that decide the game
A four is four stones that need one more to make five, and it must be answered immediately. An open four has both ends free, so it cannot be blocked and wins on the next move. An open three is three stones that can become an open four; if it is ignored for one move it turns into an unstoppable threat, so it also demands an answer.
Almost every win comes from making two threats with one stone: a four-three (a four and an open three at once) or, where allowed, a three-three. The opponent can only block one of them. Strong players also chain fours together: each four forces a reply, which lets you place stones exactly where you want until a double threat appears. This is called a VCF, a victory by continuous fours, and the hard computer looks for it on every move.
How to beat the computer
Start in the centre and keep your stones close together. Shapes near the middle can grow in all eight directions; shapes on the edge cannot.
Before every move, check the opponent's threats first: any four, then any open three. Blocking one move late is how most games are lost.
Block an open three on the side where the opponent has more room, so the remaining line is as short as possible.
Build several loose twos that cross each other. Two lines crossing at one empty point are the seed of a four-three.
Start on Easy, move to Medium once you win regularly, and turn on move numbers after a loss to replay where the threat began.
Gomoku, Omok and Renju
The game is known as Gomoku in Japan, Omok in Korea and Wuziqi in China, and it is usually played with Go stones on a Go board. Renju is the tournament form with the forbidden moves for Black, and it has its own world championships. Because the board, the stones and the goal are so simple, a full game rarely lasts more than ten minutes, which makes it a good warm-up for the deeper board games on this site.
Two players take turns placing stones on the intersections of a 15×15 board, Black first. The first to line up five of their own stones in a row — horizontally, vertically or diagonally — wins. If the board fills up with no five, the game is a draw.
What is a double-three (3-3) and why is it forbidden?
A double-three is a single move that creates two open threes at the same time. The opponent can only block one, so the other becomes an open four and wins. Because Black already moves first, many rule sets forbid Black from playing it to keep the game balanced. On this page the No double-three and Renju rules mark those points with a red cross.
Which rule set should I choose?
For a casual game, Free-style or No double-three is closest to how most people play at home. If you want a fair game where moving first matters less, choose Renju. Standard rules are the international Gomoku rules: exactly five wins and six in a row does not.
How strong is the computer?
Easy plays reasonable shapes but sometimes misses your threats. Medium always blocks fours and open threes and builds its own. Hard also searches for forced wins by continuous fours and avoids moves that let you start one, so it punishes a single late block. It respects the forbidden points whenever it plays Black.
Can I play with a friend on one phone?
Yes. Choose “Two players” and pass the device back and forth. Undo takes back one move at a time in this mode, and turning on “Tap twice to place” prevents accidental taps on a small screen.
Is Gomoku the same as Connect Four?
They share the idea of making a line, but they play very differently. In Connect Four pieces drop to the lowest free slot of a 7×6 grid and you need four; in Gomoku you can place a stone on any empty point of a much larger board and you need five, so the game is far more open.
Does Black really have an advantage?
Yes. Free-style Gomoku on a 15×15 board has been solved as a win for the first player with perfect play. In everyday games the advantage is smaller, but it is why Renju restricts Black, and why you can choose to play White against the computer for a harder game.