Sudoku Solver
Type in any 9×9 Sudoku puzzle and solve it instantly.
Last updated
How to solve a sudoku
- Click a square and type the given digits, leaving blanks empty, or paste all 81 characters at once.
- Fix any clashes highlighted in red.
- Click Solve.
About this tool
Click a square and type a digit 1–9 (or use Tab / arrow keys to move around, Backspace to clear). Leave a square blank for the solver to fill in. Conflicting digits — the same number twice in a row, column, or 3×3 box — are highlighted in red as you type, and the puzzle won't solve until they're fixed.
You can also paste a whole puzzle into any square: 81 characters, reading left to right and top to bottom, with 0 or a full stop for each blank.
The solver uses backtracking with constraint checking: it always works on the square with the fewest possible digits left, tries each one, and backs up whenever it hits a dead end. It also keeps looking after the first answer, so it can tell you whether your puzzle has exactly one solution (as a proper sudoku should), several, or none at all.
Nothing typed here is sent to a server — the entire solver runs as JavaScript in your browser tab.
Questions about solving sudoku
Can it solve any sudoku?
Any valid 9×9 puzzle, including the hardest ones, usually instantly.
How do I paste a whole puzzle?
Paste 81 characters into any square, reading left to right and top to bottom, with 0 or a full stop for each blank.
Does it check there is only one solution?
Yes. It keeps searching after the first answer and tells you if the puzzle has more than one solution, as a proper sudoku shouldn’t.
Where can I play sudoku?
Try the free sudoku game, with new puzzles at easy, medium and hard levels.