How this works in your browser
The board is held as nine cells, and after every move all eight possible winning lines, three rows, three columns and two diagonals, are checked for three matching marks. A full board with no line found is declared a draw. The complete game tree is small enough to be exhaustively analysed, which is how tic-tac-toe came to be one of the first games proved to be a draw under perfect play, and it is a standard teaching example for game-tree search precisely because the whole space fits comfortably in memory. Everything runs in the page with no state stored between sessions.
Who uses Tic-Tac-Toe
A quick two-player break
Play a round with someone beside you without installing anything.
Keeping children occupied
A simple game on a shared phone or tablet.
Teaching game strategy
Show why the game is always a draw between players who know it.
Settling something trivially
Play a round to decide who does the next thing.
Frequently asked questions
Is this single-player or two-player?
Two-player, played by taking turns on the same device.
Does it detect all winning combinations?
Yes, all 8 possible winning lines are checked after every move.
Can I restart mid-game?
Yes, click "New game" at any point to clear the board and start over.
Is there a way to always win?
No, and that is the notable thing about the game. Tic-tac-toe is solved: with perfect play from both sides it is always a draw. Two players who both know what they are doing will never win again, which is precisely why it is a children’s game and why it comes up so often in discussions of game theory.
What is the best opening move?
A corner. It creates more potential winning lines than an edge and sets more traps than the centre against an inexperienced opponent. Taking the centre in reply is the only move that reliably holds a draw against a corner opening.
Why is there no computer opponent?
Because a correctly implemented one would be unbeatable, and playing an opponent that can only draw or win gets tedious immediately. Two people on the same device is the version of this game that is actually fun.
Is anything saved between games?
No. The board exists only in the open page, and a refresh clears it entirely.