Sudoku solver, explained step by step
Type in your sudoku and get the next step explained: first the technique, then the digit if you want it.
Tap a cell and enter the givens. Skip empty cells with 0.
Paste a sudoku as text
81 characters, row by row; empty cells as 0 or a dot.
How the solver works
- Enter: Tap a cell and type the digit; the input then moves to the next cell, and 0 skips an empty one. Or paste the sudoku as text.
- Next step: The solver first checks that the sudoku has exactly one solution. Then it names the easiest technique that moves you forward and marks where to look.
- Show the digit: Tap again and it places the digit the step leads to. Its digits appear in a different colour.
Which techniques it knows
The solver thinks like a person and always takes the easiest technique that applies. These are the same techniques every puzzle at Sudoku Sagax is checked with:
- Singles: a cell has only one candidate left, or a digit fits only one place in a row, column or box.
- Pointing: if a digit sits in only one row of a box, it drops out of the rest of that row.
- Pairs and triples: two or three cells sharing two or three digits, see naked pair, hidden pair and naked triple.
- X-Wing and Swordfish: patterns across several rows and columns, see X-Wing and Swordfish.
- XY-Wing and XYZ-Wing: three cells that restrict each other, see XY-Wing.
If none of them applies, the solver says so honestly and places a safe digit so you can carry on.
Rather solve it yourself?
Every puzzle at Sudoku Sagax can be solved without guessing, in four levels from easy to extreme. In the game a hint names the next technique without giving away the digit.
Hard sudoku · Extreme sudoku · Printable sudoku · Solve sudoku without guessing
Frequently asked questions
Does the solver give away the digit right away?
No. First it names the technique and marks the area where it applies. Only when you tap again does it place the digit, so you can keep thinking for yourself.
What if my sudoku has more than one solution?
Then the solver tells you. A proper sudoku has exactly one solution; with several you would have to guess somewhere, and no technique explains a guess. Usually a given is missing or was typed in wrong.
Can I enter a sudoku I have already started?
Yes. Enter the givens and the digits you have placed so far. If one of your digits is wrong, the puzzle no longer has a solution, and the solver tells you before it helps further.
Is my input saved or sent anywhere?
No. The solver runs entirely in your browser. Your sudoku never leaves your device.