Sudoku Solver
Enter the given numbers from any valid Sudoku puzzle and get the full solution instantly.
How to Use the Sudoku Solver
- Enter the known numbers into the grid (leave the rest blank).
- Click "Solve."
- The full solution fills in, with solved cells shown in a different color.
Frequently Asked Questions
How does the solver actually work?
It uses a backtracking algorithm — it tries placing valid numbers in the emptiest, most constrained cells first, and backtracks whenever it hits a dead end, until every cell is filled correctly. This is a standard, well-understood way to solve any valid Sudoku puzzle.
What if the puzzle I entered isn't valid?
The solver first checks that your given numbers don't already break the rules (no repeated number in any row, column, or 3×3 box). If they do, it tells you the puzzle is invalid instead of attempting to solve it.
Can every valid-looking Sudoku puzzle be solved?
No — a puzzle can be validly entered (no rule violations yet) but still have no possible solution, or have more than one valid solution if too few numbers were given. This solver will report if no solution exists for what you entered.
Is my puzzle sent anywhere?
No — solving happens entirely in your browser using JavaScript, so nothing you enter is ever sent to a server.