Gomoku rules: how to play five in a row

The basic rules

• Two players, one colour each — usually black and white, or X and O.
• The first player places a stone, then the players alternate, one stone per turn.
• Stones never move and are never captured; the board only fills up.
• The first player to form five in a row horizontally, vertically or diagonally wins immediately.
• If the board fills with no line of five, the game is a draw.

Free-style gomoku versus blocked-ends caro

In the casual Vietnamese caro rule a line of five does not count if both of its ends are already blocked by enemy stones. The rule exists to cut down the first player's advantage.

Free-style gomoku does the opposite: five in a row wins regardless of what sits at either end, and a line of six or more still counts. That is the rule the Chesslizar board uses — a 12 by 20 grid where five consecutive stones end the game.

Why moving first is an advantage

On an unbounded board, free-style gomoku is a proven first-player win — it was solved by computer in 1993. Tournaments therefore add a balancing rule.

The two common ones are Renju, which forbids the first player from making certain shapes such as double-three, double-four and overlines, and swap openings, which let the second player take the other colour after the opening stones. Friendly games rarely bother, but knowing they exist settles an argument mid-game.

Shapes you must recognise

• Open three: three in a row with both ends empty. Left alone it becomes an open four, which cannot be stopped.
• Open four: four in a row with both ends empty — a win, because only one end can be blocked.
• Closed four: four in a row blocked at one end; it still forces the opponent to answer at the other end.
• Double threat: one stone creating two threats at once, two open threes or a four plus a three. This is how most games are actually won.

Tips for beginners

Do not only block. Every defensive stone should also extend a line of your own, or you will just chase your opponent until the board runs out.

Play towards the centre: a central stone lies on four directions that can still grow, an edge stone on two. Opening in a corner is the classic beginner's loss.