How to play Sudoku
A clean grid, a pencil-note tool and explanations that help you understand one logical step at a time.
Select a cell, then a number. Use Notes for candidates.
- Fill every empty cell with a digit from 1 to 9. Each row, column and 3×3 box must contain each digit exactly once. The given digits cannot be changed.
- Select a cell and then a number, or use the keyboard. Notes mark possible candidates without entering an answer. Erase removes your entry; Undo restores a previous move.
- Every generated puzzle has one solution. Easy puzzles solve with singles, Medium adds locked candidates and naked pairs, and Hard may require triples or hidden pairs. Difficulty reflects the required logic, not just blank count.
- Hints explain a placement or a candidate elimination. Correct conflicting or wrong entries first. Error highlighting can be switched off. There is no time limit or forced loss after mistakes.
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First visit each game while online. Then this browser can reopen visited games without a connection. Clearing site data removes these copies and saves.