International rules · 8 min

International Gomoku Rules: Gomoku and Renju Explained

Gomoku and renju are both five-in-a-row games, but renju adds forbidden moves for Black to balance the first-move advantage. Understanding both helps you read every gomoku variant correctly.

What is gomoku?

Gomoku is the Japanese name for the five-in-a-row game, also known as five in a row or gobang. Two players alternate placing stones on a 15×15 board, and the first to connect five stones horizontally, vertically or diagonally wins. There is no capturing and no movement after placement. The game is easy to teach, which is why it appears in classrooms and living rooms as well as in serious competition. Its short rules also make it a good first strategy game for younger players.

Basic gomoku rules

Black moves first.
Players alternate placing one stone on an empty intersection.
Five consecutive stones with no gap win the game.
No capturing, and no moving a stone after it is placed.
The standard board is usually 15×15.

How is renju different from gomoku?

Renju is the competitive variant in which Black has forbidden moves. Black may not create a double open three, a double four, or a line of more than five stones; committing a forbidden move loses the game immediately. White is not restricted in the same way. The purpose is to reduce the first player's advantage, which is considerable in free-style gomoku when both players are strong. Learning the forbidden shapes is therefore part of learning renju, not an optional extra. In practice, Black must attack accurately without crossing the line, while White tries to build a position where any aggressive reply becomes illegal.

Common variants

Free-style gomoku: no forbidden moves, which makes it suitable for casual play.
Renju: competitive play with forbidden moves for Black.
Swap2: an opening protocol used to balance the position.
Caro in Vietnam: usually five in a row, with local rules that can vary.

Which version should you play?

Beginners should start with free-style gomoku to get comfortable with open threes, open fours and double threats. Once those patterns feel natural, try renju to understand why tournaments need forbidden moves. Caro Classic currently plays free-style gomoku on an expanded board, so there are no forbidden moves to track and no capture rules to remember. The simpler rules let you focus on shape and timing. If you later move to renju, the attacking ideas carry over; only the limits on Black's strongest shapes are new.