Solve sudoku step by step to learn how to solve sudoku puzzle. Current support technique: Naked Single, Hidden Single, Pointing, Claiming, Naked Subset, Hidden Subset, X-Chains, XY-Chains, XYZ-Chains. If the input puzzle is not valid then you can get a correct result, or if the puzzle you input is too hard to solve by the utility then you won't get a correct result either.