The Rules of Tic-Tac-Toe

Tic-tac-toe is a two-player game played on a 3x3 grid. Players alternate turns marking empty squares with their symbol — X or O — and the first to align three of their marks in a row wins. If the grid fills with no three-in-a-row, the game is a draw.

Setup

• The board is a 3x3 grid of nine empty squares.
• One player is assigned X; the other is assigned O. X moves first by convention.
• There are no scores, timers, or pieces beyond the two marks.

Turn order

1. X plays first, placing a mark in any empty square.
2. O plays next in any empty square.
3. Players alternate turns until the game ends.
4. A mark may not be placed in an occupied square.
5. Moves are permanent — marks cannot be moved or removed.

Winning

A player wins immediately upon placing their third mark in an uninterrupted line. The eight possible winning lines are:

• The three rows (top, middle, bottom)
• The three columns (left, middle, right)
• The two diagonals (top-left to bottom-right, top-right to bottom-left)

Draws

If all nine squares are filled and neither player has completed a three-in-a-row, the game is a draw (sometimes called a “cat’s game”). Draws are common between experienced players — in fact, with optimal play from both sides, every game ends in a draw.

Edge cases and clarifications

• Can a player skip a turn? No. In standard tic-tac-toe there is no “pass”; every player must place a mark on their turn.
• Does O move first after X wins a round? There is no universal rule. In casual play, the loser often opens the next round; in competitive variants, alternation is common.
• What if two winning lines form simultaneously? This is possible in a fork. The moving player still wins — they only needed to complete one line.
• Are diagonal wins always valid? Yes. In standard tic-tac-toe, the two main diagonals count as winning lines.

Related: Strategy Guide · Glossary · Variants

Last updated April 22, 2026