Tic Tac Toe IO
Play classic tic tac toe on boards from 3x3 to 21x21. Challenge friends, the computer, or online players and line up 3 or 5 marks in a row before your opponent.
Tic Tac Toe IO takes the old paper-and-pencil game and stretches it far beyond the usual nine squares. You can play on a small 3x3 grid or scale up to a huge 21x21 board, pick how many marks you need in a row, and choose whether to face a friend, the computer, or a stranger online.
Tic Tac Toe IO: Build Your Own Match
Before each round, you decide how the game will go. These are the options you can change:
- Board size: anything from 3x3 up to 21x21.
- Winning line: 3 or 5 marks in a row.
- Difficulty: Easy, Medium, or Hard when you play the computer.
- Move timer: an optional countdown for each turn.
The goal never changes: line up your marks in a straight row before your opponent does. What changes is how much thinking the board demands. A small grid ends in seconds, while a large one turns into a long fight for space.
Pick Your Opponent
Online
Jump into a live match against a player from anywhere in the world. Every opponent plays differently, so no two games feel the same.
Two Player
Share one device with a friend and take turns clicking. It works well when you want a quick rematch without any setup.
Vs Computer
Play against the AI at the difficulty you chose. Start on Easy to learn the rhythm, then move up when you can spot its traps early.
Playing on a Bigger Board
The classic 3x3 game is easy to solve, since a careful player rarely loses. Bigger boards change that. With 5 in a row on a wide grid, you can no longer rely on memorized patterns. You have to build several threats at once, block lines before they connect, and keep an eye on the whole board instead of one corner. Turning on the timer adds pressure and makes you decide faster.
Controls
Everything is done with the mouse. Click a square to place your mark. In Two Player mode, you and your friend take turns using the same mouse on the same screen.