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Rules and strategy guide

How to play tic tac toe

The complete rules of tic tac toe — also called noughts and crosses — plus the eight winning lines, the fork tactic that actually wins games, and why two good players always draw.

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What is tic tac toe?

Tic tac toe is a two-player strategy game played on a 3×3 grid of nine squares. One player marks squares with X, the other with O, and they take turns until one player has three of their marks in a straight line — or until the grid is full. It is called noughts and crosses in British English, where the nought is the O and the cross is the X.

The rules, step by step

  1. Draw a 3×3 grid. Tic tac toe is played on a grid of nine empty squares, three across and three down. One player takes X, the other takes O.
  2. X makes the first move. The player using X places a mark in any one of the nine empty squares. By convention X always starts.
  3. Alternate turns. Players take it in turns to place one mark in any square that is still empty. Marks cannot be moved once placed, and you cannot mark a square your opponent has taken.
  4. Build a line of three. Try to place three of your own marks in a straight line — along a row, down a column, or across either diagonal — while stopping your opponent doing the same.
  5. Win, or fill the board. The first player to complete a line of three wins immediately. If all nine squares are filled and neither player has a line, the game is a draw.

How do you win at tic tac toe?

You win by completing a line of three of your own marks. There are exactly eight ways to do it on a 3×3 grid: three horizontal rows, three vertical columns, and the two diagonals. The moment you complete any one of those eight lines, the game ends and you have won.

The eight winning lines

Numbering the squares 1 to 9 from the top left, the winning lines are:

Notice how often square 5 appears. The centre sits on four of the eight lines, each corner sits on three, and each edge square on only two. That single fact drives almost all tic tac toe strategy.

What is a draw?

A draw happens when all nine squares are filled and neither player has completed a line of three. Nobody wins and nobody loses. In some places this is called a "cat's game". Draws are the normal outcome between two players who are both paying attention.

Basic strategy

Every turn, work through the same three questions in order. Most losses come from skipping one of them.

  1. Can I win right now? If any single square completes a line for you, take it and the game is over.
  2. Can they win next move? If your opponent has two in a line with the third square open, you must take that square.
  3. What is the strongest square left? Centre first, then a corner, then an edge.

The fork — how you actually win

Against anyone who follows those three rules, you will never win by building a single threat: they will simply block it. To win you need a fork — one move that creates two separate lines of two at the same time. Your opponent can only block one square per turn, so the other line wins for you on the following move.

The classic fork starts in a corner. Play a corner; if your opponent replies anywhere other than the centre, take the opposite corner. You now threaten a diagonal, and with your next corner you can open a row and a column at once.

Defending against a fork

If you spot your opponent setting up two threats, do not just block one of them. Instead make a threat of your own that they are forced to answer, which steals the tempo they needed. If no such move exists, take a square that sits on both of their potential lines.

Why do so many games end in a draw?

Tic tac toe is a solved game: mathematicians have checked every possible sequence of moves. When both players play perfectly, the result is always a draw. Neither X nor O can force a win. This is why the Hard opponent in Tic Tac Toe can never be beaten — playing perfectly and being unbeatable are the same thing here.

That is also why the game is a good teaching tool. Once you can reliably draw every round, you have understood it completely, and the interesting part becomes spotting the moment your opponent slips.

Tic tac toe and noughts and crosses

They are the same game. "Tic tac toe" is the American name and "noughts and crosses" is the British and Irish one. The rules, the grid and the eight winning lines are identical, so anything on this page applies to both.

Try it now

Reading about a fork is one thing; building one is another. Play a few rounds against Medium — it blocks single threats but cannot see a fork coming, which makes it the perfect opponent to practise on.

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FAQ

Common questions about the rules

Short answers on winning, drawing and turn order.

How do you win at tic tac toe?

You win by placing three of your marks in a straight line — across a row, down a column, or along either diagonal. There are eight possible winning lines on a 3×3 grid. The strongest opening is the centre square, because it belongs to four of those eight lines.

What happens if nobody wins?

The round is a draw, sometimes called a "cat's game". A draw happens when all nine squares are filled and no line of three has been completed. Draws are common — between two players who both know what they are doing, almost every game of tic tac toe ends this way.

Is tic tac toe the same as noughts and crosses?

Yes — they are the same game under two names. "Noughts and crosses" is the usual British name, "tic tac toe" the American one. The nought is the O and the cross is the X. The rules, the 3×3 grid and the eight winning lines are identical in both.

Who goes first in tic tac toe?

X always moves first, in both the browser game and the Android app. This is the standard convention and it matters: with perfect play from both sides the game is a draw, but X has more chances to force a mistake. Against the computer you always play as X.