Nine tic-tac-toe boards inside one big board, where every move decides where your opponent must play next. Challenge a Monte Carlo AI at three levels or pass the device to a friend.
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You (X)0
Draws0
Computer (O)0
Your move: play anywhere
How to play Ultimate Tic Tac Toe
The big board is made of 9 small tic-tac-toe boards. X moves first and may play in any cell.
Where you play decides where your opponent must play. If you mark the top-right cell of a small board, your opponent's next move must go in the top-right small board.
Get three in a row inside a small board to win that board. It is then marked with your symbol and closed.
If you are sent to a board that is already won or full, you may play in any open board.
Win three small boards in a row (across, down or diagonally) to win the game. If no one can, the game is a draw.
Highlighted boards show where the next move is allowed.
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How to use the Ultimate Tic Tac Toe
Choose a mode. Play vs Computer (pick Easy, Medium or Hard and whether you are X or O) or 2 players on the same device.
Make the first move. X starts and may play in any of the 81 cells.
Follow the highlighted board. The cell you choose inside a small board sends your opponent to the matching small board.
Win small boards by getting three in a row inside them; a won board shows a big X or O and is closed.
Win three small boards in a row to win the game. Use Undo or Show hint whenever you are stuck.
Ultimate Tic Tac Toe rules at a glance
Situation
What happens
First move of the game
X may play in any of the 81 cells.
You play in cell position N of a small board
Your opponent must play in small board N (same position on the big board).
Three in a row inside a small board
That board is won and closed; it counts as one mark on the big board.
A small board fills up with no winner
It is closed as a draw and belongs to nobody.
You are sent to a closed board
You may play in any open small board.
Three won small boards in a row
That player wins the whole game.
All boards closed, no line of three
The game is a draw.
Strategy tips
Every move is two decisions: where you mark inside a board, and which board you hand to your opponent. A great local move can be a bad move if it sends them where they win immediately.
The center board is the most valuable: it belongs to four of the eight winning lines on the big board, the corners to three and the edges to two. The same weighting applies inside each small board.
Send your opponent to finished boards carefully: a move that sends them to a closed board gives them a free choice anywhere, which is often a gift.
Sacrifice small boards: letting your opponent win a board that is not on a useful line can be fine if it keeps them out of the boards that matter.
Use the hint: the hint runs the same Monte Carlo search as the computer and highlights the move it likes best, which is a good way to learn patterns.
How the Monte Carlo AI works
Monte Carlo tree search repeats four steps thousands of times: selection walks down the tree choosing moves with the UCT formula (average result + c·√(ln parent visits ÷ child visits)), expansion adds one new move, simulation plays the rest of the game with fast semi-random moves, and backpropagation records the result along the path. The move visited most often is played. More thinking time means more simulations, which is why Hard is noticeably stronger than Easy.
Frequently asked questions
What are the rules of Ultimate Tic Tac Toe?
The board is a 3×3 grid of small tic-tac-toe boards. X moves first anywhere. After that, each move must be made in the small board that matches the position of the previous move inside its small board: a move in the top-left cell sends the opponent to the top-left board. Three in a row inside a small board wins that board, and three won boards in a row wins the game.
What happens if I am sent to a board that is already won or full?
Then you may play in any small board that is still open. This tool uses that common rule, and closed boards cannot receive further moves, so every small board has a single owner.
How does the computer opponent think?
It uses Monte Carlo tree search (MCTS): it plays out thousands of quick random games from the current position, keeps statistics on which moves lead to wins, and focuses its search on the most promising moves with the UCT formula. Hard simulates for about 1.8 seconds per move, Medium for 0.7 seconds and Easy for a fraction of that, plus some random moves.
Is Ultimate Tic Tac Toe solved like normal tic-tac-toe?
Normal tic-tac-toe is a known draw with perfect play. Ultimate Tic Tac Toe has vastly more positions, and under the rules used here it has not been fully solved by brute force, so strategy and reading ahead really matter.
Can a game end in a draw?
Yes. If every small board is won or full and no player has three won boards in a row, the game is a draw. Some players use a tiebreak that counts won boards, but this tool scores it as a draw.
What is a good strategy?
Avoid sending your opponent to a board where they can win immediately or to the center board early. Think about where each move sends the other player, try to force them into boards that are already decided, and aim to win the center and corner small boards because they belong to the most winning lines.
Is my game saved?
Only your settings and the scoreboard are saved in your browser's local storage on this device. Nothing is sent to a server.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.