How to play Sudoku
New to Sudoku? Start with the core rules, then use the built-in controls and hints to solve puzzles step by step.
1. Learn the rules
Place digits 1 through 9 so every row, column and 3×3 box contains each digit exactly once.
2. Find singles
Look for cells where only one candidate is possible, then find digits with only one possible position in a row, column or box.
3. Use notes
Select an empty cell and turn on Notes to track candidates when a puzzle becomes harder.
4. Use hints
Hints explain a logical next move before you apply it. They can identify naked singles, hidden singles, diagonal constraints and Killer cage combinations, and they flag a wrong digit before you build on it.
Keyboard controls
- 1–9: enter a digit.
- Backspace/Delete/0: erase.
- P or N: toggle Notes.
- Ctrl/Cmd + Z: undo.
- Arrow keys: move the selected cell.
- Tab: move focus between the board and the controls.
New to the rules? See what Sudoku is first. Ready to go further? See Sudoku solving tips and advanced techniques.
A simple solving routine
- Fill in every cell that has only one candidate (a naked single).
- For each digit, check whether any row, column or box has just one place left for it (a hidden single).
- Turn on Notes and mark candidates in the cells that are still open.
- Look for pairs and other patterns that remove candidates. See Sudoku tips & techniques.
- Stuck? Ask for a hint. It explains the next logical step before you apply it.
Common beginner mistakes
- Guessing instead of deducing. A valid puzzle never needs a guess.
- Checking only the row and forgetting the column and 3×3 box.
- Skipping notes on harder puzzles, which makes later steps harder to see.
- Not going back over the whole grid after placing a digit. One new digit often unlocks a cell elsewhere.
Easy, Medium and Hard
Every mode offers Easy, Medium and Hard puzzles. Easy is the gentlest place to learn the singles. Medium and Hard puzzles reward using notes and spotting more advanced patterns. Each is checked to have exactly one solution.
Playing other modes
Diagonal Sudoku adds two extra groups to check; see the Diagonal Sudoku guide. Killer Sudoku replaces most givens with cage sums; see the Killer Sudoku guide and combinations cheat sheet.