Tic-Tac-Toe Strategy: How to Win and Never Lose

Tic-tac-toe looks like a game of luck, but it isn’t. A short list of priorities is enough to never lose, and a couple of traps will win you plenty of games against friends who don’t know them. This tutorial plays through a first game move by move, then explains forks, the best replies to each opening and a practice plan you can try right away on the Tic-Tac-Toe board.

What you will learn

• Why corners and the center are stronger than edges.
• How to spot and block a threat every single turn.
• What a fork is and how to set one up.
• The two classic traps, and the one reply that avoids each of them.
• A simple priority list that guarantees at least a draw.

If you are still new to the rules themselves, read the tic-tac-toe rules guide first. It takes two minutes. This tutorial numbers the squares 1 to 9 row by row, from the top left (1) to the bottom right (9).

Your first game, step by step

Here is a short game between Maya (X, going first) and Leo (O). Follow along on a piece of paper or on the board.

1. Maya takes a corner (square 1). Corners belong to three lines, so they give her several ways to build later. The center would be just as good.

2. Leo answers in the center (square 5). This is the only reply to a corner opening that is completely safe. Every other answer lets a perfect X player force a win.

3. Maya takes the opposite corner (square 9). Now she has two marks on the 1-5-9 diagonal, but Leo already sits in the middle of it, so there is no threat yet. She is setting a trap: if Leo answers in a corner, she gets a fork.

4. Leo plays an edge (square 2). Good defense. By playing an edge he makes his own threat (2-5-8), which forces Maya to respond instead of building.

5. Maya blocks at square 8. Always block first. Now Maya has 8 and 9 in the bottom row, a threat at 7.

6. Leo blocks at square 7. That also gives him 5 and 7 on the 3-5-7 diagonal, so Maya must block again.

7. Maya blocks at square 3. The rest of the game is a sequence of forced blocks.

8. Leo and Maya fill the last squares, each blocking the other, and the board fills with no line of three. It is a draw.

That game is what good tic-tac-toe looks like: both players block every threat, and neither falls for a fork. To win, you need your opponent to make a mistake, and the next sections show you where those mistakes happen.

The priority list

Before every move, run down this list and do the first thing that applies:

1. Win. If you have two in a row and the third square is empty, take it.
2. Block. If your opponent has two in a row with an empty third square, take that square.
3. Fork. If one move creates two threats at once, play it.
4. Stop a fork. If your opponent could fork next turn, make a threat of your own that forces them to block somewhere harmless, or take the square they need.
5. Take the center if it is free.
6. Take a corner, ideally the one opposite your opponent’s corner.
7. Take an edge only when nothing above applies.

Steps 1 and 2 alone will make you better than most casual players. Steps 3 and 4 are where games are actually decided.

How forks win games

A fork is a single move that creates two threats at once. Your opponent can only block one of them, so you win with the other. Here X has just played square 7, holding 1, 5 and 7. X now threatens the left column at square 4 and the diagonal at square 3, and O cannot stop both:

How did O get here? After X opened in the corner, O played an edge (square 2) instead of the center. X took the center, forcing O to block the diagonal at 9, and then square 7 made the fork. One weak reply on move two was enough.

The two classic traps

Trap 1: corner, then opposite corner

When X starts in a corner and O correctly takes the center, X can take the opposite corner. Now O’s natural instinct is to grab another corner, and that loses: X blocks, and the block itself creates a fork. The defense is an edge square. Playing an edge makes a threat of its own, and X is forced to answer it instead of setting up a fork, as in the sample game above.

Trap 2: center, then opposite corner

When X starts in the center and O takes a corner, X can again take the opposite corner. This time the safe answer is the reverse: O must take one of the two remaining corners. If O plays an edge, X blocks and creates two threats at once.

These two positions look almost the same, but the right answer is opposite. That is why so many people lose to them. Remember it as: against two opposite corners, play an edge; against center plus corner, play a corner.

Openings at a glance

Going first is a small advantage, but tic-tac-toe is a solved game: with perfect play from both sides it is always a draw. Your goal against a strong player is to never lose; your goal against everyone else is to give them chances to make the mistakes above.

Common beginner mistakes

• Not looking at the whole board. Most losses come from missing a threat on a diagonal. Check all eight lines before every move.
• Making a threat instead of blocking. A threat doesn’t help if your opponent wins on their next move. Block first.
• Grabbing edges early. Edges belong to only two lines, so they rarely help you build.
• Using the same opening every time. A friend who has played you before will know the replies. Switch between corners and the center.

A practice plan

1. Play three games against Easy on the computer and focus only on steps 1 and 2 of the priority list. You should win most of them.
2. Move up to Medium. It always wins or blocks when it can, so you will need forks to beat it. Try both traps above.
3. Play Hard as O. Answer every opening correctly and hold the draw. If you can draw ten games in a row, your defense is solid.
4. Play a friend with the pass screen on, alternating who starts with Rematch, and keep score for the session.

When tic-tac-toe starts to feel too small, the same ideas of threats and forks carry over to Four in a Row, where gravity limits where you can play, and to Gomoku, where you need five in a row on a much bigger board.