Gomoku (Five in a Row) Rules and Winning Patterns: Open Three, Four, and Double Threats

2026-11-09 · 8 min read

Gomoku is easy to learn and hard to explain. The rules take one sentence: be the first to get five stones in a row. The vocabulary takes longer. Open three, sleeping three, open four, four-three and double three all describe threats, and the player who sees threats one move earlier usually wins.

The rules in one minute

Gomoku is played on a 15×15 board with 225 intersections. Stones go on the intersections, not inside the squares. Black places the first stone, then players alternate. A stone never moves and is never removed.

The first player to make five stones in a row wins. The five must be connected horizontally, vertically, or diagonally. This site uses free-style gomoku: five or more in a row counts as a win, and there are no forbidden moves. If the board fills with no five in a row, the game is a draw. Black gets 113 stones and White gets 112 on a full 15×15 board.

Tournament renju adds restrictions. Black may not create a double three, a double four, or an overline of six or more; those are fouls and lose the game. White is not restricted and wins with five or more. The strategy below applies to both versions. When a pattern is a renju foul, the text says so.

The patterns you need to name

Almost every gomoku commentary is built from the words three and four. Learn these and the board becomes readable.

Open three

An open three is a line of three stones that can become an open four with one more stone. The simple shape is three in a row with both ends empty. On the row, Black on E5, F5 and G5 with D5 and H5 empty is an open three. Black can play D5 or H5 and create a four with both ends open.

Sleeping three

A sleeping three is a three that is blocked on one end or has a gap, so one more stone can make at most a four with a single winning point. It is still a threat, but it is one level weaker than an open three. Blocking one end of an open three turns it into a sleeping three.

Open four

An open four is four stones in a row with both ends empty. It has two winning points. The opponent can block only one, so an open four wins on the next move unless the opponent can win immediately. If your opponent has an open four on the board, you are already lost.

Four (rush four)

A four is any shape that threatens five on exactly one point. The opponent must block that point immediately. A four forces a reply, which makes it a useful tempo move even when it does not win by itself.

Four-three

A four-three is one move that creates a four and an open three at the same time. The four forces the opponent to block. While they spend that move on defense, the open three becomes an open four, and the open four cannot be stopped. This is the most common winning combination in practice.

Double three and double four

A double three is one move that creates two open threes. The opponent can block one, but the other becomes an open four. A double four creates two fours at once. In free-style gomoku both are legal. In renju, Black is forbidden from playing either; White may.

Overline

An overline is six or more stones in a row. In free-style gomoku it is a win. In renju, Black's overline is a foul, while White's overline wins.

Why double threats win

A single threat is a question with one answer. A four forces one block. An open three usually forces one block. The defender answers and survives.

Two threats in one move are different. If one move creates a four and an open three, the defender must answer the four. The open three is still there, and on the next move it becomes an open four. If one move creates two open threes, the defender can block only one; the other becomes an open four.

This is why strong players stop counting stones and start counting threats. A move that makes one three is a plan. A move that makes a four and a three is a win, unless the defender has a counter-four that forces you to answer first.

One four-three on the board

Put Black on G8, H8 and I8, with a White stone on F8. Black also has stones on J6 and J7. Black now plays J8.

The row G8–J8 is four Black stones. F8 blocks one end, so K8 is the only point that makes five. That is a four, and White must block K8 or lose immediately.

The file J6–J8 is three Black stones, with J5 and J9 both empty. That is an open three. When White blocks K8, Black plays J9. Now J6–J9 is a four with J5 and J10 both empty. White can block one end; Black plays the other and wins.

The combination assumes White has no counter-four. If White's forced block on K8 also creates a four, Black must answer that threat first, and the sequence changes. Always check what the defender's forced move does.

Three attacking principles

1. Make forcing moves. A four forces a block. An open three forces a reply. Every forcing move keeps the initiative and gives you another turn to build. A move that threatens nothing lets the opponent choose the next direction.
2. Aim for two threats, not one. One four is blocked. One open three is blocked. Four-three, double three and double four cannot all be answered. Build toward a move that creates two problems at once instead of adding a fourth stone to a single line.
3. Stay connected and play toward the center. The center has more lines running through it, so a stone there can serve two or three directions. A long line near the edge has one side closed and is easier to block. A group of stones that supports several threats is worth more than one beautiful line.

How to defend

When the opponent makes an open three, do not wait. Block one end immediately, or create a four of your own that forces them to respond. If you ignore it, they make an open four and the game is over.

When the opponent makes a four, block the single five point. Do not block an open three instead. The four wins now; the open three only wins later.

When you block, look at what your block creates. The best defense is often a block that also builds your own three. A purely passive block gives the initiative back.

Common questions