Tic Tac Toe is a board game, played with two players, O and X. Each player takes turns marking the spaces in a 3×3 grid, either in rows or diagonally. The players then move their tokens to the next available space, alternating between players. A player wins by having a line of three of its symbols on the grid.

If a player ends a turn on an empty space, it goes to the end of the game. The game ends when one player has no more moves.

In its original form, the game is played with a pencil and paper, but in recent years has appeared on the smartphones of both players.