How to Play

The idea in one line

Solve a Sudoku, but every 3x3 box you complete becomes yours. Line up three of your boxes — row, column, or diagonal — and you win, exactly like Tic-Tac-Toe.

The board

TicTacToku uses a standard 9x9 Sudoku grid: 81 cells, divided into nine 3x3 boxes. Those nine boxes also form a 3x3 Tic-Tac-Toe grid — three boxes across, three down. Some cells start pre-filled as fixed clues; the rest are yours to solve.

Placing digits (the Sudoku part)

Select a cell, then choose a digit 1–9. A move is legal only if it follows Sudoku rules:

• No repeated digit in that cell's row.
• No repeated digit in that cell's column.
• No repeated digit in that cell's 3x3 box.

Illegal moves are rejected on the spot — the conflicting cells are highlighted so you can see why. Fixed clue cells cannot be changed.

Claiming a box (the Tic-Tac-Toe part)

When your move fills the last empty cell of a 3x3 box — all nine cells filled, all valid — you immediately claim that box. It gets tinted with your symbol:

A claimed box is locked to its owner unless they erase a cell inside it to release it.

Winning the match

The nine boxes are a Tic-Tac-Toe grid. You win the instant you own three boxes in a line:

• Any of the 3 rows of boxes.
• Any of the 3 columns of boxes.
• Either diagonal.

If no one makes a line

It is possible for all nine boxes to be claimed without anyone forming a line. Then it goes to a majority tiebreak: whoever owns the most boxes wins. Because nine boxes can never split evenly — the closest is 5–4 — this always produces a winner, so a true draw cannot happen.

How a match plays out

TicTacToku is a real-time race. Both players receive the same puzzle and solve their own private copy at the same time. You never see your opponent's digits — only the boxes they claim appear on your board, tinted X or O with no numbers behind them. Whoever's move completes a box first claims it on both screens. Speed and accuracy together win the match.

Accounts, opponents, and ranking

• Guest play: jump in with no sign-up. Optional Google sign-in keeps your username and stats across devices.
• Opponents: you are matched with another player. If none is available, a bot steps in so you can always play.
• Ranking: wins and losses adjust your ELO rating and place you on the global leaderboard.

Your first match, step by step

1. Tap Play and let a match start.
2. Pick a box you can finish quickly — one with the fewest empty cells.
3. Fill its cells with legal digits until the box is complete and claimed.
4. Aim your next boxes so three of yours line up in a row, column, or diagonal.
5. Watch your opponent's claimed boxes and block their line if they get close.

Ready to put it into practice?

Want to win more? Read the Strategy guide.