Tic-Tac-Toe vs Bug

The bug has pulled up a chair for a game of XO. You play X, the bug plays O, and the first to get three in a row wins the round. Think you can out-play it?

How to play Tic-Tac-Toe (XO) against the bug

1. Place your X
Click or tap any empty square on your turn. The bug answers automatically with an O after a moment of thinking.
2. Get three in a row
Line up three marks horizontally, vertically or diagonally to win the round. If all nine squares fill up first, it's a draw.
3. Play the next round
Press play again. The first move alternates between you and the bug every round, so nobody keeps the advantage of starting.

How smart is the bug?

The bug always takes a winning square when it has one, and always blocks you when you're one move away from three in a row. In smart mode it usually plays the best possible move, but now and then picks a different safe move, which gives a sharp player the chance to set up a fork and win. In unbeatable mode it searches every possible continuation of the game (the minimax algorithm) and never loses: the best you can do is a draw.

Tips to beat the bug

Start in a corner when you move first. Corners take part in three winning lines, and a corner opening gives you the most ways to create a fork, two threats at once that can't both be blocked. When the bug opens, take the centre if it's free. Against unbeatable mode, aim for a draw; against smart mode, keep creating double threats.

Frequently asked questions

Are my scores saved?

Yes, for the current browser session. Scores survive page reloads and are cleared when you close the tab. Use reset scores to start the count again at any time.

Does the game need an internet connection or an account?

No account is needed. Once the page has loaded, the game and the bug's AI run entirely in your browser, and nothing is sent to a server.

Is Tic-Tac-Toe the same as the XO game or noughts and crosses?

Yes. It's the same game with different names in different countries: Tic-Tac-Toe in the US, noughts and crosses in the UK, and the XO or OX game in India and many other places.