What Is Notakto? The Tic-Tac-Toe Where You Only Play X

Notakto is tic-tac-toe with three rules changed, and the changes rewrite everything. There is no O: both players place the same mark, an X, and you play not on one grid but across two or three at once. Completing a three-in-a-row no longer wins. It kills a board, and finishing the last board loses. The rules take a few seconds to learn; the game underneath is fully solved and, as it turns out, a disguised game of Nim.

Notakto (pronounced no-tak-toe) is impartial, misère tic-tac-toe. “Impartial” means both players have exactly the same moves available: there is no “your mark” and “my mark”, only X. “Misère” means the usual goal is reversed: making the line is the thing you must avoid. The name is a play on “tic-tac-toe”; the game is also known as neutral or impartial tic-tac-toe, because both players use the same mark.

Because a single grid is a quick trick to master (more on that below), Notakto is really a multi-board game. Here we play it across two or three standard 3×3 boards side by side, which is where it stops being a novelty and starts demanding genuine thought.

How to Play

1. Start with two or three empty 3×3 boards.
2. On your turn, place one X on any empty cell of any board that is still live. Both players use X.
3. When a board has three X marks in a line (row, column, or diagonal), that board is dead and leaves play.
4. Completing a line on any board except the last is free; that board simply dies and the game continues on the others.
5. Complete the three-in-a-row on the last live board and you lose.

A game is short, a few minutes at most, and it can never end level. Someone always draws the losing line.

One Board: Centre, Then a Knight’s Move

Play Notakto on one board and it collapses into a trick. The first player marks the centre, then answers every reply with a knight’s move away from it (two cells along and one across, as a chess knight moves). Played that way, the opponent is always the one forced to complete a line.

That is why we never offer a one-board mode to play against: it is solved in a single sentence, and there is nothing to think about once you know it. The interesting game begins when there is more than one board to juggle, and the one-board trick quietly returns as a tactic, because each board you can hand to your opponent already lost is a small trap of its own.

Why Multi-Board Is the Real Game

With two or three boards in play, your move on one grid changes the balance of all of them. Killing a board removes it from the count; refusing to kill one keeps it alive as a threat. The whole game becomes a question of who is forced to finish the final board, and steering toward or away from that point is the entire art. The strategy for that is its own piece: how to win at Notakto.

Why a Draw Is Impossible

Notakto has no draws. A board can hold at most six X’s without a line, so every board dies by its seventh mark. The last death falls to one specific player, and that player loses. Exactly one loser, every time. That guarantee is what lets the game be solved at all, and it is the hallmark of a misère game, where completing the pattern is the losing move, a connection Notakto shares with its sibling, Triad.

Is Notakto Solved?

Yes, for the boards we play on. Perfect play is known, and the theoretical winner is fixed before the first mark. At the Perfect level our computer opponent never plays a losing move it could avoid; Casual and Sharp slip on purpose so you can win. What “solved” means here, and the genuinely open question lurking just past it on the 4×4 board, is covered in is Notakto solved? The reason it can be solved so cleanly is the secret that the boards are Nim heaps in disguise.

Where It Came From

Notakto is younger than it looks. According to the usual account, it was devised in 2010 after a five-year-old suggested that both players in tic-tac-toe should just be X, and it was solved a few years later. The full story (the nephew, the mathematicians, and the Numberphile videos that gave it an audience) is in the history of Notakto. For how it differs from the schoolyard original, see Notakto versus tic-tac-toe.

Keep Exploring

The fastest way to understand Notakto is to lose a few games to it. Play Notakto now, try each of the three levels, and watch how the boards trade off; then come back and the strategy pieces will read very differently.