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Gomoku

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About Gomoku (Five in a Row)

  • Black and White take turns placing stones on a 15×15 board
  • The first to get 5 in a row — horizontally, vertically or diagonally — wins
  • Stones are never captured; you only ever play on empty points

How to play

  • Click (or tap) an empty intersection to place a black or white stone
  • Choose "vs Computer", "2 Players" or "Online" to start
  • Against the computer, choose a difficulty and your color, then press "Start game"
  • Online, enter a nickname and press "Find an opponent" (60 seconds per move, no sign-up)
  • You can change settings and restart at any time from "⚙️ Mode / Settings"

How to Win at Gomoku ― Strategy and Tips: the Four-Three and Double Three

The heart of every Gomoku winning strategy is to create several threats at once, more than your opponent can block in a single move. Keep your opponent busy defending, take the initiative, and keep attacking — that is the basic plan. Below are the attacking tactics that take you beyond beginner level, in the order they lead to a win.

Two shapes to learn first ― the "four" and the "three"

  • Four = a shape that makes five with one more stone. Your opponent must block it or lose, so a four forces their reply.
    Fig. 1 Four: a four blocked on one side. The only point that makes five is a, so filling it stops the four. But your opponent is forced to answer.
    Fig. 2 Open four: Also called: straight four. a four with both ends open. Black makes five at either a or b, so it can no longer be stopped: the game is won.
  • Split four = a four with one empty point in the middle. Even though the stones don't look connected, playing the gap makes five. Most "I suddenly lost" games come from missing this.
    Fig. 3 Split four: a four with one gap. Playing a makes five, so even though it looks like two and two, you must block it just like a four. The same goes for a one-and-three split.
  • Open three = three in a row with both ends open. Left alone it becomes an open four, so your opponent has to respond.
    Fig. 4 Open three: a three with both ends (a, b) open. Left alone it becomes an open four next move, so when your opponent makes one you must respond.
  • Closed three = a three blocked on one side. Extending it only makes a four, so there is no hurry to block it. The only difference from an open three is whether the ends are open.
    Fig. 5 Closed three: a three blocked on one side. Extending it only makes a four, so there is no rush to block it. The only difference from an open three is whether the end is open.
  • Split three = a three with one gap. It belongs to the open-three family: left alone it becomes an open four. There are three points that block it, and the gap in the middle is the key point.
    Fig. 6 Split three: a three with one gap. Because it doesn't look connected, it is the shape players miss most. To block it, the circled point (the gap) is the key.

This sense of "forcing your opponent to respond" is the foundation of attack. Always try to grow your own threes and fours while tying down your opponent's moves.

Winning tactic ①: the four-three

A single move that creates a four and an open three at the same time. Your opponent has no choice but to block the four, and meanwhile you extend the three into an open four (a four with both ends open), which can no longer be stopped. The diagram below shows the five moves from Black ① to five in a row. This is the core tactic of Gomoku strategy.

Fig. 7 Four-three: ① creates a horizontal four and a vertical open three at the same time. White has to block the four with ②, and meanwhile ③ turns the vertical line into an open four (a four with both ends open). Whichever end White ④ fills, ⑤ makes five.

Winning tactic ②: the double three (3-3)

A single move that creates two open threes at once. Your opponent can block only one, and you turn the other into an open four to win. The diagram below shows the sequence from Black ① to five in a row. The trick is to aim for the point where two of your lines cross.

Fig. 8 Double three: Also called: 3-3. ① creates two open threes at once. White can block only one with ② (here, the horizontal one), and the remaining diagonal becomes an open four with ③. Whichever end White ④ fills, ⑤ makes five. In free-style Gomoku (no forbidden moves) this is a main weapon.

Winning tactic ③: the quiet setup move ― build the four-three one move ahead

"Make a four-three," they say — but you can't find one. That is the most common wall beginners hit. A four-three isn't something you make on the spot; it is something you prepare one move earlier. The diagram below is a whole game in which Black wins with ⑲, starting from ① on the center point. White makes perfectly ordinary defensive moves, blocking Black's twos and threes. So why does White still lose? Let's follow the moves.

Fig. 9 The quiet setup move: White correctly blocked the threes from ⑨ and ⑪. But the remaining ends of those threes, a and b, are the seeds of fours. The quiet move ⑬ makes both a and b four-three points. White blocks a with ⑭, but ⑮ at b is a four-three.
  • ①–⑧: Each time Black makes a two, White either blocks an end (④⑧) or plays between the stones (⑥). So far White is defending well
  • ⑨–⑫: Black makes two diagonal open threes (⑤③⑨ and ⑦①⑪). White blocks one end of each with ⑩ and ⑫. Both threes look stopped
  • ⑬ is the setup move: a blocked three still becomes a four if you play its other end (a or b). ⑬ is a quiet move between a and b that makes neither a three nor a four. But now playing a gives "diagonal four + horizontal three", and playing b gives "diagonal four + vertical three" — there are two four-three points
  • ⑭–⑲: White blocks a with ⑭ (correctly stopping a dangerous point). Even so, ⑮ at b is a four-three. White blocks the four, ⑰ makes the vertical line an open four, and ⑲ completes five

Does it click now? White blocked the threes with ⑩ and ⑫ and stopped a dangerous point with ⑭. Every one of those was a correct defense. White still lost because the single move ⑬ created two four-three points at once, and White can only block one point per move. Even a blocked three stays alive — its remaining end is "the seed of a four". You are attacking, yet only your opponent is busy. That is the quiet setup move.

Even when you could make a four or a three right away, first look for a move that creates a point where your next move would be a four-three. Like a and b in the diagram, the open end of a blocked three remains "the seed of a four". On defense, after you block a three, keep an eye on whether its other end is about to cross another of your opponent's lines.

Winning tactic ④: decoy and main attack ― draw the eye with a three, then strike

The setup move is quiet, so a strong opponent may block the point before you can use it. That is where a decoy comes in. Make a three your opponent must answer, and with that same move, prepare the real four-three point. The diagram below is a whole game in which Black wins with ⑲, starting from ① on the center point.

Fig. 10 Decoy and main attack: the diagonal open three from ⑬ is the decoy. White must block it with ⑭ (blocking the other end changes nothing). But ⑬ is also material for the vertical line, and a was the crossing of a horizontal four and a vertical three. ⑮ at a is a four-three.
  • ①–⑫: Each time Black makes a two or three, White blocks it from the end (④⑥⑧⑫). ⑩ is played between Black's stones. So far White is defending well
  • ⑬ is the decoy: a diagonal open three. Left alone it becomes an open four, so White must block it with ⑭. Blocking the other end leads to the same result
  • The real attack is vertical and horizontal: ⑬ is a diagonal three, but it is also material for the vertical "⑬ – gap – ⑤". Horizontally, ①③ and ⑪ sit two points apart, so playing a creates a horizontal four and a vertical three at the same time
  • ⑮–⑲: ⑮ at a is a four-three. White blocks the four with ⑯, ⑰ makes the vertical line an open four, and ⑲ completes five

The key to a decoy is to spend your opponent's turn with a move they must answer (an open three or a four). Busy blocking the three in front of them, they don't notice the other line the same stone is building. On defense, before you block a three, ask yourself: "Is any stone in this three also part of another line?"

Winning tactic ⑤: continuous fours (VCF)

Keep playing fours, forcing a reply every time, until you win. VCF stands for "victory by continuous fours". A four can be blocked at only one point, so your opponent cannot play anywhere else. Because no threes are involved, the big advantage is that you can read it out all the way to the end.

Fig. 11 Continuous fours: play a four with ① and White must answer at ②. Using that gained tempo, ③ makes a vertical open four, and White can no longer stop it. Winning without ever giving your opponent a choice — that is VCF.

When you see a position where you might make two or more fours, trace it before you play — "four → they block → next four → …" — and look for an open four or four-three at the end.

Opening principles

Black starts on the center point. The number of straight lines of five that pass through a point is 20 at the center, 8 at the middle of an edge, and only 3 in a corner — the closer to the center, the easier it is to make lines cross.

The third move ― Kagetsu and Hogetsu: the shape made by the first three moves (Black 1, White 2, Black 3) is called an opening in Renju. When White 2 is placed directly next to the center (above, below, left or right) it is a direct opening; when it is diagonally next to it, an indirect opening. Combined with where Black 3 goes, there are 26 openings in total. You don't need all of them — the two recommended for beginners are Kagetsu (direct) and Hogetsu (indirect).

Fig. 12 Kagetsu: if White 2 is placed directly above the center (next to it vertically or horizontally = a direct opening), Black 3 goes to the right of White 2. Black 1 and Black 3 line up diagonally.
Fig. 13 Hogetsu: if White 2 is placed diagonally next to the center (an indirect opening), Black 3 goes to the right of Black 1, directly below White 2.

Kagetsu and Hogetsu are openings where a winning line for Black is known even in Renju, which has forbidden moves. In Gomoku without forbidden moves, Black wins even more easily. If White 2 comes from a different direction than in the diagram, just rotate the board and play Black 3 where it makes the same shape. Memorizing sequences only goes so far, though: once your opponent leaves the book, you have to play on your own. As the Renju proverb goes, "learn the openings, then forget them and play" — keep the idea of the shape in mind (opening diagrams and names follow Renju no Kiso by the Tokai Renju Association).

The diagram below is an example opening in which Black reaches a four-three on move 13 even though White defends normally.

Fig. 14 An example opening: Black 1–7 spread out from the center diagonally and with one-point jumps. Black 9 makes a vertical open three and 11 a diagonal one, forcing White 10 and 12 to block; then 13 makes a vertical four and a horizontal open three together (a four-three). White defends normally, yet the blocking stones drift away from Black's lines.
  • Black 1–8: spread your stones. Expand from the center diagonally and with one-point jumps, without making threes yet. Don't line stones up in a straight row; spread them in L-shapes and diagonals to plant the seeds of a four-three.
  • Black 9 and 11: force replies with threes. Make an open three and White has to block it (White 10 and 12). Choose points that both attack and plant the next three, and Black's stones gather toward the four-three crossing while White is busy answering.
  • Black 13: four-three. A vertical four and a horizontal open three appear together. White can only block the four, and next the horizontal line becomes an open four — Black wins.

Good shapes for attacking

From the opening into the middle game, arranging your stones into shapes that are easy to attack from is called "building". The classic three-stone shapes for Black have names in Japanese Renju.

Fig. 15 Saddle: Also called: kuragata. a two bent at a right angle
Fig. 16 Tower: Also called: yagura. diagonal twos built into a roof shape
Fig. 17 Bent Nail: Also called: kugiore. a diagonal two bent sideways at the tip

The point of all three is that the stones are not in one straight line: they form twos pointing in different directions. Count the points where your next move makes an open three: the Saddle has 12 (in three directions — vertical, horizontal and diagonal), the Tower has 11 (three directions), and the Bent Nail has 8 (two directions). A three built in one straight line is finished once White blocks that line, but White cannot erase all the options of a good shape in one move.

Fig. 18 Why the Saddle is strong: playing any circled point makes an open three (12 points across vertical, horizontal and diagonal). White cannot erase them all in one move.

As you stack good shapes, points appear where a three crosses a three, or a three crosses a four. Stones ①③⑤ in the setup-move diagram actually form a Tower. Your opponent will be building good shapes too, so taking the key point of their shape first is also a fine defense.

How to defend

  • Block your opponent's open three before it becomes a four. A three with both ends open is your top priority.
    Fig. 19 Blocking correctly: block from the side where your opponent's stones are gathered. Even if Black extends to a, it is only a four, which can be stopped next move.
    Fig. 20 Blocking wrongly: block from the open side and Black's red-marked move makes a horizontal four (five at a) and a diagonal open three at once. Same open three, but blocking from the wrong side flips the result.
  • Always block a four. Ignoring it means losing on the spot.
  • Don't just block — look for moves that defend while extending your own line, killing two birds with one stone.

Practicing against the computer

Start on a low difficulty to get a feel for making four-threes and double threes yourself, then raise the difficulty and practice reading your opponent's threes and fours ahead of time — that builds the strength to beat human players too. Practicing as both Black and White is recommended. After a loss, look back and check whether you missed a split three or split four.

FAQ

Is it better to play first or second in Gomoku?

In Gomoku without restrictions, the first player (Black) has the advantage. In this game you can choose either color, so you can practice both sides.

Is there a guaranteed way to win Gomoku?

Yes — in unrestricted Gomoku, the first player is known to have a winning sequence. The key is tactics like the "four-three" and "double three" that create several threats at once.

What are forbidden moves like double three, double four and overlines?

They are restrictions placed on the first player in competitive rules such as Renju. This game uses simple Gomoku rules with no forbidden moves, so beginners can jump right in.

How can I get better at Gomoku?

The fastest way is to practice making four-threes and double threes against the computer. Also make sure you never miss your opponent's open threes, and block them in time.