Sudoku Solver
Solve any Sudoku instantly — or get just the next logical step, explained in plain English, so you can keep solving yourself.
Type the givens into the grid (arrow keys move, Backspace clears), or paste a puzzle below. Then solve it in one go or step by step.
Solving steps
What the solver does
- Solve fills the whole grid and lists every logical step it used, from scanning and singles to pairs, X-Wings, XY-Wings and coloring.
- Next step reveals just one more digit and the reasoning behind it — ideal when you are stuck and do not want the whole answer.
- Check puzzle confirms the puzzle is valid: no repeated digits, at least 17 givens and exactly one solution. It also estimates the difficulty using the same scale as our puzzles.
Everything runs in your browser; the puzzle you enter is not sent anywhere. You can link straight to a puzzle by adding its 81 characters after a # in the address, for example /sudoku-solver/#53..7....6..195….
How it works
The solver first applies human techniques in order of difficulty, always choosing the simplest one that makes progress: full houses and hidden singles, naked singles, locked candidates, naked and hidden pairs, triples and quads, X-Wing, Swordfish and Jellyfish, XY-Wing and XYZ-Wing, W-Wing and simple coloring. The hardest technique it needs determines the difficulty rating.
Some extreme puzzles need techniques beyond that toolkit, such as long forcing chains. For those, the answer is found by an exhaustive backtracking search, which also proves whether the puzzle has one solution, several, or none.
Seeing "more than one solution"? Published puzzles occasionally contain a typo. Double-check each given against the source.