Gomoku is a classic game of five in a row, played with stones on a board or with pencil and paper. Two players take turns marking squares, and the first to line up five wins. In Vietnam it is called Caro, and generations of students have played it on the squared pages of their notebooks. Play here against a friend on one device, invite a friend to play online, or test yourself against the computer.
Gomoku rules
- The game is played on a grid of 15 by 15 squares. You can also choose a larger 19 by 19 board.
- One player is X and the other is O. X always moves first, then the players alternate.
- On your turn, mark any empty square. Marks stay where they are for the rest of the game.
- The first player to make an unbroken line of five or more marks wins. The line can run across, down or diagonally.
- If every square fills up and nobody has five in a row, the game is a draw.
The "Block both ends" rule
Caro players in Vietnam often add one more rule, which you can turn on in the game setup. A line of exactly five does not win if your opponent has already marked the squares at both of its ends. This makes attacking harder, because a line that is already capped at one end can be stopped by capping the other.
Under this rule a line of six or more still wins, and the edge of the board does not count as a block.
How to play on this page
- Choose your opponent: the computer or a friend sharing your device. To play a friend on their own screen, press "Play with a friend online" and send them the link.
- Against the computer, pick Easy, Medium or Hard, and decide whether to go first as X or second as O.
- Click or tap an empty square to place your mark. The last move is highlighted so that you can always see what just happened.
- On phones and tablets, "Tap twice to place" is on from the start: tap once to see where your mark will go, then tap again to place it. You can turn it off in the game setup.
- Use Undo if you change your mind. Against the computer it takes back its reply and your move.
- When someone wins, the line is struck through and the result goes on the score. Your settings and score are saved in this browser.
Tips for winning
- Start near the center. A mark in the middle of the board can grow in every direction, while one by the edge cannot.
- Watch for three in a row with both ends open. If it is left alone it becomes an open four, which cannot be stopped, so answer it straight away.
- Build two threats with one move. A single mark that extends two lines at once forces your opponent to choose, and they can only stop one.
- Block in a way that also helps you. The best defensive move is one that extends a line of your own.
- Keep looking at the diagonals. They are the easiest lines to miss, for you and for your opponent.
Frequently asked questions
- Are Gomoku and Caro the same game?
- They are the same basic game: get five in a row on a grid. Gomoku is the name most widely used in English, and Caro is the Vietnamese name. Players in Vietnam often add the "Block both ends" rule, which you can turn on here.
- Do I need to download anything or sign up?
- No. The game runs in your browser on a computer, tablet or phone. There is nothing to install and no account to create.
- Does a line of six count as a win?
- Yes. Five or more in an unbroken line wins here, even with "Block both ends" turned on. Only a line of exactly five can be cancelled by that rule.
- How strong is the computer?
- Easy plays casually and sometimes overlooks things, which makes it a good place to learn. Medium always takes a win and always blocks a threat, but it does not plan ahead. Hard looks several moves ahead and searches for forced wins, so expect a real fight.
- Does the first player have an advantage?
- Yes. Moving first is a real advantage in five in a row, especially without the "Block both ends" rule. To even things out, take turns going first, or choose to play second against the computer for a tougher challenge.
- Will my score be saved?
- Yes. Your settings, your score and the game in progress are saved in this browser, so they will still be here when you come back. They are not sent anywhere, and clearing your browser data removes them.