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Sudoku Checker — Is Your Puzzle Correct?
Check a Sudoku for mistakes and validity. Enter or scan your grid and find out instantly whether it has a unique solution, no solution, or more than one — and exactly where it conflicts.
Find conflicts and dead ends
As you enter digits, the checker highlights any that break the rules — the same number twice in a row, column or box. Press Solve and it tells you whether the clues have one solution, none at all (a contradiction), or many (too few clues), so you know if a puzzle is well-formed before you waste time on it.
Check your own solving
Part-way through a puzzle and unsure if you have gone wrong? Enter what you have and the checker flags any rule conflicts, and a single hint can confirm whether the next move you were considering is actually justified.
Validate a puzzle you created
Setting puzzles? The checker confirms a grid has exactly one solution — the mark of a proper Sudoku — and points out under-constrained grids that allow more than one answer.
Prefer to practise? Pick a level — easy, medium, hard or expert — or read the strategy guides. Other tools: solver, photo scanner, hint and checker.