Tic Tac Toe Strategy: How to Never Lose (and When You Can Win)

Tic Tac Toe is a solved game. If both players play correctly, every game is a draw, which means you can never lose unless you make a mistake, and you can only win when your opponent makes one. This guide gives you the moves that never lose, the traps that win against anyone who is not paying attention, and the reason a timed version like Blitz Tic Tac Toe is still hard even when you know all of this.

1. The short version
2. What is the best first move?
3. How to respond when you go second
4. What is a fork and how do you make one?
5. How do you stop a fork?
6. The complete priority list
7. How many games are there?
8. Beating Blitz Tic Tac Toe

The short version

On every move, in this order: win if you can, block if you must, make a fork if you can, stop your opponent's fork, take the centre, take the corner opposite your opponent, take any corner, take any edge. Follow that list and you will never lose. The rest of this guide explains why.

What is the best first move?

Number the squares like a phone keypad, 1 to 9 from top left to bottom right. There are only three genuinely different opening moves: a corner, the centre, or an edge.

• Corner (1, 3, 7 or 9) is the strongest opening. A corner is part of three lines, and against a corner opening the second player has exactly one safe reply, the centre. Every other reply loses to correct play. If you want to win against humans, open in a corner.
• Centre (5) is the safest. The centre is part of four lines, the most of any square. Against a centre opening the second player must take a corner; an edge reply loses. The centre opening is very hard to lose with but gives fewer chances to trap an opponent.
• Edge (2, 4, 6 or 8) is the weakest. It is not a losing move, but it gives the opponent the most safe replies and the fewest traps for you.

How to respond when you go second

Going second, your job is to draw. Memorise three responses:

• Opponent opens in a corner: take the centre. Nothing else is safe.
• Opponent opens in the centre: take a corner. Taking an edge loses to a fork.
• Opponent opens on an edge: take the centre. Then block as needed.

After that, the priority list below takes over. The most common way second players lose is by taking the opposite corner after a corner opening. It feels symmetrical and safe. It is a forced loss.

What is a fork and how do you make one?

A fork is a move that creates two winning threats at once. Your opponent can only block one, so you win on the next move. Forks are the only way to win against someone who blocks single threats correctly.

The classic fork from a corner opening: X takes corner 1, O takes centre 5 (correct), X takes the opposite corner 9. If O now takes another corner, say 3, X takes the last corner 7 and threatens both 4 and 8. O can only block one.

The correct reply for O at move four was an edge, not a corner. Taking an edge forces X to block and leaves no fork. That is the pattern behind most forks: they come from corners, and the defence is usually to take an edge that forces the attacker to respond.

How do you stop a fork?

There are two ways, and one is better than the other.

1. Make a threat of your own that forces a block, as long as the square your opponent is forced into does not itself create a fork for them. This is the best defence because it takes the initiative.
2. Occupy the fork square directly. If your opponent has one specific square that would create two threats, sit on it.

Spotting forks early is the whole skill of the game. Whenever your opponent has two pieces that share no line, look for the empty square that would connect each of them to a third. If one square does both, that is the fork square.

The complete priority list

This order comes from the 1972 analysis by Allen Newell and Herbert Simon and is still the simplest perfect strategy. On each turn take the first that applies:

1. Win. If you have two in a row with the third square empty, take it.
2. Block. If your opponent has two in a row, block the third square.
3. Fork. Make a move that creates two ways to win.
4. Block a fork. Stop the opponent's fork, preferably by making a threat they must answer.
5. Centre. Take it if it is empty.
6. Opposite corner. If your opponent is in a corner, take the corner diagonally opposite.
7. Empty corner.
8. Empty edge.

How many games are there?

There are 255,168 possible games of tic tac toe if you count every legal sequence of moves. Of those, the first player wins 131,184, the second wins 77,904 and 46,080 are draws, which is why beginners think going first is a big advantage. Once you remove rotations and reflections there are only 26,830 distinct games, and once both players play perfectly there is only one result: a draw. The whole game tree fits comfortably in a phone's memory, which is why every tic tac toe app can play perfectly.

Beating Blitz Tic Tac Toe

Blitz Tic Tac Toe on Indextring takes the same solved game and adds two things that undo all of the above: a clock and five boards. You are X, the computer is O, and the computer moves first on every board. After each of your moves the board slides away and the next of five boards arrives, so you are playing five games interleaved, with 1.5 seconds per move on the default setting.

The computer is not perfect. Its rules, in order, are: take a win, block your win, otherwise pick randomly from the centre and free corners, then edges. It never makes forks deliberately and it never blocks a fork. That gives you a plan:

• Respond correctly to its opening. If O opens in the centre, take a corner. If O opens in a corner, take the centre. Do this on autopilot; the clock is for thinking about forks, not openings.
• Set up a fork. Since the computer only blocks single threats, a fork wins every time. After O centre, X corner, O random, look for the square that creates two lines.
• Never leave O two in a row. If a winning O line exists after your move, the game ends immediately. Under time pressure this is how almost every loss happens.
• Remember the board you just left. Each board comes back after four others. Keeping a mental note of where the fork square is on board two while playing boards three to five is the real difficulty.

Win three in a row on any board and you win the game. Survive a full rotation of all five without O connecting three and you also win. Easy mode gives you two seconds per move if you want to practise the fork patterns before you take on the 1.2 second clock. Play it here, free, in the browser.