How to win at Tic Tac Toe: the strategy that never loses

The short answer

Play X first and start in a corner. If your opponent does not answer in the centre, you can force a win. If you play second, take the centre if the first move was a corner, and take a corner if the first move was the centre. Block every line that has two of your opponent’s marks, and look for a move that creates two threats at once: a fork.

lightbulb Perfect play from both sides is always a draw. You win when your opponent slips, so make the first move count.

Know the board

The 3 by 3 board has nine squares: four corners, four edges and one centre. There are eight winning lines: three rows, three columns and two diagonals. The centre belongs to four lines, a corner to three, and an edge to only two, which is why centre and corners are the strong squares.

If you play first (X)

1. Open in a corner. It gives the most ways to win.
2. If O replies anywhere except the centre, you can force a win with a fork, as described below.
3. If O takes the centre, take the corner opposite your first mark. The draw is safe, and it sets a trap: if O now takes a corner, you win with a fork.
4. Always check first whether you can win this move, then whether you must block.

If you play second (O)

1. If X opens in a corner, take the centre. Any other reply loses against perfect play.
2. If X opens in the centre, take a corner. Taking an edge loses.
3. If X opens on an edge, take the centre, which is safe and strong.
4. Do not start your own attack until you have blocked every immediate threat.

The fork: two threats at once

A fork is a move that creates two different lines where you need only one more mark to win. Your opponent can only block one of them, so you win next turn. Setting up forks is how almost every win happens, and spotting your opponent’s forks before they happen is how you avoid losing.

When you are defending, if your opponent can fork, either take the fork square yourself or make a threat that forces them to block, so they never get the chance.

A turn-by-turn checklist

1. Can I win right now? If yes, do it.
2. Must I block? If the opponent has two in a line with an empty third, block it.
3. Can I make a fork? Take it.
4. Can the opponent make a fork? Stop it by taking that square or making a forcing threat.
5. Take the centre, then an opposite corner, then any corner, then any edge.

Practise against the computer

The fastest way to make this automatic is to play lots of short games. The Tic Tac Toe app from Robince Studio is free for Android and is a collection of 29 games including Snake, and you can also play Tic Tac Toe in your browser on this site.

Frequently asked questions

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