How to play Tic-tac-toe

1 player vs computer, or 2 online

Get three of your marks in a row — across, down or diagonally — on a three-by-three grid, before your opponent does.

The rules, step by step

1. 1

   The grid is three squares by three. You play crosses; the computer plays noughts.

2. 2

   Take turns. On your turn, tap any empty square to put your mark in it.

3. 3

   The first player to fill a whole line of three — a row, a column or one of the two diagonals — wins.

4. 4

   If all nine squares are filled and nobody has a line, the game is drawn.

5. 5

   The opening move alternates between games, so a run of losses is never just a run of second moves.

Three tips that change how you play

• Take the centre if it is free. It is on four of the eight lines; a corner is on three and an edge on two. More lines through your square means more ways to build a threat and more of your opponent's threats already blocked.
• Play for a fork, not for a line. Any single threat gets blocked. Two threats at once cannot both be blocked, and setting one up is the whole game — two opposite corners plus the centre is the classic shape.
• When your opponent has two opposite corners and you have the centre, take an edge rather than a corner. Taking a corner walks straight into the fork; an edge forces them to answer instead.

The fork, worked through

You open in the top-left corner. Your opponent answers on an edge — say the middle of the top row — instead of taking the centre. You take the centre. They block your diagonal by taking the bottom-right corner. Now you play the bottom-left corner, and look at what you have: crosses on top-left, centre and bottom-left. The left column is yours with two of three and the top-left-to-bottom-right diagonal is blocked, but the bottom-left-to-top-right diagonal is now yours with two of three as well. Two lines, each one square from finishing, and the squares are different. They block one; you play the other and win. Nothing clever happened. They gave up the centre on move two, and every game where that happens ends the same way.

Three mistakes that cost beginners the game

Building your own line and forgetting to look at theirs.

Every turn, check their two-in-a-rows before your own. Taking your own win beats blocking theirs, but only if the win is actually there this turn — otherwise blocking comes first. This is the mistake that loses more games than every other one put together.

Opening on an edge.

An edge square sits on two lines and gives the opponent the centre. Open in the centre, or in a corner if you want to play for the two-corner fork. There is no plan that starts with an edge.

Assuming a draw means you played well.

Against the hard opponent it does. Against easy it means you missed something: easy does not block at all, so any two-in-a-row you build should finish. If you are drawing with easy, you are answering its moves instead of making your own.

Common questions about Tic-tac-toe