Play tic tac toe online against the computer or a friend on the same screen. The computer has three levels, from a casual easy mode to an unbeatable one that plays perfectly on 3×3. Bigger 4×4 and 5×5 boards need four in a row, and the score is kept for each mode.
How to use
- Choose vs Computer or 2 players, a board size and, against the computer, a level.
- Tap a square to place your mark. X always moves first.
- Get three in a row on 3×3, or four in a row on 4×4 and 5×5: across, down or diagonally.
- After a round, tap Next round. The score for each mode and level is kept.
- Change who starts in Options: you, the computer (or X, O) or take turns.
- Unbeatable plays perfect minimax on 3×3: the best you can get is a draw. It picks at random among equally good moves, so games still vary.
- On 4×4 and 5×5 the Hard computer searches several moves ahead within a short time limit.
- Undo against the computer takes back your last move and its reply.
How to win tic tac toe
X moves first and gets three in a row across, down or diagonally to win. Played well by both sides, 3×3 tic tac toe always ends in a draw, which is why the unbeatable level can never lose.
As X, take a corner first. If O does not answer in the center, you can usually set up a fork: two lines that each need one more mark, so O can only block one. As O, answer a corner with the center and an opening in the center with a corner.
Levels and board sizes
Easy makes plenty of mistakes and suits children. Medium blocks obvious threats but misses forks. Unbeatable uses a full minimax search on 3×3 and picks at random among equally good moves, so its games still vary. On 4×4 and 5×5 you need four in a row; the Hard computer looks several moves ahead within a short time limit, which makes those boards a real challenge without being solved.
Frequently asked questions
Can you beat the unbeatable tic tac toe AI?
No. On 3×3 the best result against perfect play is a draw. If you win, the level was set to Easy or Medium.
Who goes first in tic tac toe?
X always moves first. In Options you can choose whether you, the computer or the players take turns starting each round.
Is tic tac toe always a draw?
Yes, with perfect play from both players a 3×3 game always ends in a draw. Wins only happen after a mistake.
How many in a row do you need on 4×4 and 5×5?
Four in a row on both. That gives more room for forks than the 3×3 game and makes draws less certain.
Can two people play on one phone?
Yes. Choose 2 players and pass the device back and forth. Undo takes back the last move and the score is kept for each mode.
Does the score stay after I close the page?
Yes. Scores for each mode and level are saved in this browser until you reset them.