Play a freshly generated Sudoku with a guaranteed unique solution, get hints, or reveal the solution. Every puzzle is built on your device — nothing is fetched or sent.
Strategies (in order of usefulness)
1. Naked single — a cell with only one possible number left.
2. Hidden single — a number that can only go in one cell of a row, column or box.
3. Candidate elimination — cross out numbers that already appear in the same row, column or box.
4. Last resort for hard puzzles — the engine behind this tool uses backtracking with candidate shuffling: try a number, and if the search dead-ends, undo and try the next.