Tic-tac-toe alternates X and O on empty squares. Our edition has three board sizes but two winning lengths. Moving beyond 3×3 therefore changes more than the number of empty squares you must watch.
In this guide
Which line wins?
On 3×3, connect three identical marks horizontally, vertically or diagonally. On 4×4 and 5×5, connect four. Marks must be consecutive: a gap does not count. Five marks are not required on 5×5; four consecutive cells within a longer row suffice.
| Board | Required line |
|---|---|
| 3×3 · 9 cells | Three |
| 4×4 · 16 cells | Four |
| 5×5 · 25 cells | Four |
A turn and the end of play
X starts in the local edition. Select an empty cell; occupied cells cannot be overwritten. Each valid move is checked for a winning line. A full board without a winner is a draw. A win ends the round immediately; the opponent does not receive one final reply.
Marks can be placed freely anywhere. There is no gravity: a diagonal needs no supporting cells below it. This separates larger tic-tac-toe boards from Four in a Row even when both require four.
How to read our study boards
Columns run a, b, c and, where present, d and e from the left. Tic-tac-toe study diagrams number rows from the top down, starting at one. Thus c3 is the third column and third row. X and O remain distinct without colour, and each study also has a text description below it.
Local settings
Choose the computer or two people on one device, 3×3/4×4/5×5 and easy/medium/hard. Two-player mode makes no computer moves. Difficulty does not change the winning length. Hard search on larger boards is bounded; “hard” does not promise a mathematically perfect solution there.
Sound and individual cue levels, reduced motion and elapsed-time display are presentation preferences. Showing the timer does not impose a move deadline. On a new page visit, Start game begins a fresh round using saved preferences rather than automatically continuing an abandoned local game.
What the live room offers
In the separate live edition, the creator selects 3×3 with three in a row or 4×4/5×5 with four, plus the starting player, before opening. Both players share the room rule; personal computer settings do not override it. Creating a room requires a confirmed account. An invited player may join as a guest with a name and the six-character code.