Sudoku Checker
Is your sudoku a real one? Paste it in to find out if it's valid, has one solution, or none. Useful for puzzles you've copied from a book or made yourself.
How to use it
- 1Type the puzzleFill in the cells with the numbers as given. Leave the empty cells blank.
- 2CheckWe'll tell you one of three things: it's valid and has one solution; it has no solution (a duplicate somewhere); or it has more than one (not really a sudoku).
- 3Fix and retestIf something's off, edit the cells and check again. Conflicts will be highlighted in red.
Checker FAQ
What does 'valid' mean here?
A valid sudoku has no duplicates in any row, column, or 3×3 box, and has exactly one solution. Both conditions need to be true.
What if my puzzle has more than one solution?
Then it's not technically a sudoku. A real sudoku has exactly one answer. Add more given clues until that's true.
What if it has no solution?
That usually means a typo. two of the same number in a row, column, or box. Look for the highlighted cells and fix them.
Does the checker tell me the answer?
No, just whether the puzzle works. Use the solver if you want the full solution.