Tic Tac Toe Rules

Tic Tac Toe has almost no hidden rules. Disputes usually come from house variants, not from the standard game. This page is the standard.

Players and marks

• Two players.
• Marks are X and O.
• X moves first unless you agree otherwise.
• Players alternate strictly. You cannot skip a turn or move twice.

Legal moves

A legal move places your mark in a single empty cell. Occupied cells are illegal. Moving after the game is already won or drawn is illegal. Online, Duetly's server rejects those moves even if a modified client tries to send them.

Winning condition

The first player to occupy three cells in a straight line wins immediately. The game ends on that move. Extra marks are not placed. Two winning lines on the same move still count as a single win for that player — you do not get bonus points in the standard game.

Draw condition

If the board is full and neither player has three in a line, the result is a draw. There is no overtime in the classic rules.

What is not a rule

• You do not have to say 'tic tac toe' after a win.
• Corner-start is not required.
• Taking the center is strong, not mandatory.
• You cannot rotate the board to create a new line that was not there.

For the feel of the game rather than the letter of it, see how to play Tic Tac Toe. To try the rules live, play a local two-player game.