Sudoku Clan › Sudoku solver, step by step
Sudoku solver, step by step
Type in any Sudoku and solve it in one press, or walk through it one logical step at a time with the reasoning for every digit.
Enter your puzzle
The solver needs JavaScript to run.
How to use the solver
- Tap a cell and enter the clues from your puzzle. On a keyboard, type the digits and use the arrow keys or space to move.
- Press Next step to see one move at a time. The message under the grid names the technique and explains why the digit goes there.
- Press Solve to fill the whole grid. The solver also tells you the hardest technique the puzzle needs and what level that makes it.
- If you already have the puzzle as text, paste its 81 characters into the box, row by row, with 0 or a full stop for empty cells.
A solver that explains itself
Most solvers hand you a finished grid. That fixes today's puzzle and teaches you nothing for tomorrow's. This one uses the same logic a person would: it looks for the easiest move available, such as a hidden single, and only reaches for harder ideas like a naked pair or an X-Wing when nothing simpler is left. Each step is explained in a sentence.
A good way to use it when you are stuck on a newspaper or book puzzle: enter the grid as it stands now, including the digits you have filled in, and press Next step once. Read the reason, then go back and carry on yourself.
It checks your puzzle too
- Repeated digits in a row, column or box are highlighted, which catches most typing errors.
- No solution: the solver tells you when a grid cannot be completed. One clue is usually in the wrong cell.
- More than one solution: a proper Sudoku has exactly one. If yours has several, the solver says so.
How the level is worked out
The solver rates a puzzle by the hardest technique needed to finish it, not by the number of clues. Hidden singles only is Easy or Medium. Naked singles make it Hard. Pointing pairs and pairs make it Expert. Triples, X-Wings, XY-Wings and Swordfish make it Fiendish. Puzzles that need even more than that are solved by trying the options, and the solver tells you when it had to do so. The technique guides explain each one.
Learn the moves, then play
The same explaining hints are built into Sudoku Clan, so you can practise on fresh puzzles at any level and ask for the reasoning whenever you are stuck. Start with how to play or go straight to a medium puzzle.
Questions
How does the Sudoku solver work?
It first looks for logical moves a person would make, from single candidates up to X-Wings and Swordfish, and explains each one. If a puzzle needs more than that, it finishes by trying the remaining options.
Can it solve any Sudoku?
Yes, any standard 9×9 Sudoku that has a solution. It also tells you when a grid has no solution or more than one.
Is my puzzle sent anywhere?
No. The solver runs in your browser. Nothing you type leaves your device.
How many clues does a Sudoku need?
At least 17. No puzzle with 16 or fewer clues has a single solution.