How to Play Sudoku

Just three rules, plus the two techniques every beginner should know.

Rules

Fill the 9x9 grid with the numbers 1 to 9.
Every row contains 1 to 9 exactly once.
Every column contains 1 to 9 exactly once.
Every 3x3 box contains 1 to 9 exactly once.

Two techniques to learn first

Only one candidate: after removing the numbers already in a cell's row, column and box, sometimes only one number is left. That's the answer.
Only one place: pick a number. Sometimes it can go in only one cell of a row, column or box. That's where it goes.

Using notes

Tap Notes to switch to pencil mode, then tap numbers to add small candidates. Tap again to remove.
When you place a correct number, it is removed from the notes in the same row, column and box automatically.

Controls

Undo: go back one move (Ctrl/⌘+Z on a computer).
Erase: clear the number or notes in the selected cell.
Hint: unlimited. It teaches in three steps: where to look, which technique, then the answer. Games with hints don't count toward the time ranking.
Keyboard: number keys to enter, arrows to move, N for notes, Backspace to erase.

→ Easy Sudoku　→ Sudoku　→ Sudoku strategies (pairs, pointing, X-Wing…)

Difficulty levels

Level	Given numbers	What it takes
Easy	40	Fill cells that have only one possible number
Medium	32–33	Same technique, fewer clues, more searching
Hard	26–28	Use notes; pairs and pointing at most
Expert	26 or fewer	Basics always stall; pairs or pointing required
Master	28 or fewer	Pairs stall; X-Wing or XY-Wing required
Extreme	26 or fewer	Even X-Wing stalls
Evil	26 or fewer	The Extreme puzzles that need the deepest reasoning. The hardest level

FAQ

Is it free?

Yes. All seven levels are free. No sign-up.

Does every puzzle have one solution?

Yes. Each puzzle is checked by the program to have exactly one solution.

Will I lose my progress if I leave?

No. Open the same level on the same device and browser to continue. One game is saved per level.

Are there ads?

We never interrupt you with ads while you're solving a puzzle.

Can I play on my phone?

Yes. No install needed. On a computer you can also use number keys, arrow keys and N to toggle notes.

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