Sudoku solver, step by step
Enter your puzzle as far as you have got, and see the next step or every step to the end, each explained the way our game's hint explains it.
Or scan with your phone
Type the puzzle's numbers, or paste all 81 at once, with 0 or a dot for each empty cell. Backspace empties a cell.
How the solver works
At every step it takes the easiest technique that finds something, as a person would: first the singles, which place a number, then the techniques that remove notes, from pairs and pointing to the X-Wing and the wings.
It starts from the numbers you entered and notes every number still possible in each empty cell. The steps after the singles work on those notes, and the board shows them.
The steps and their sentences are the ones our game's hint gives, in the same order, so what you see here is what the game teaches.
Where no pattern is left, it uses the contradiction: it supposes a number, follows the singles it forces, and removes it if the board breaks. Where even that finds nothing, it says so and shows the answer.
The techniques it knows
Your puzzle stays with you
The solver runs in your browser: the puzzle you enter is not sent anywhere, and the page sets no cookie and stores nothing. To share a puzzle, solve it here and copy the address: the puzzle is in it after the # sign, a part of an address that browsers never send to a website.
Harder than Extreme
The puzzle called the world's hardest sudoku, and six of ours that need more than any level, to print with their answers.
Questions and answers
Can it solve any sudoku?
Any classic 9×9 sudoku with one solution. It explains every step it can with the techniques our game's hint knows; on the rare puzzles where they run out, such as the one called the world's hardest, it says so and shows the answer.
Can I enter a puzzle I have already started?
Yes. Enter your numbers along with the puzzle's own, and the next step starts from where you are. If one of yours is wrong, the solver may find no solution, or solve a different puzzle, so check them first.
Does it guess?
No. Every step follows from the board. The contradiction supposes a number only to rule it out, and where the techniques run out, the solver says that the answer it shows comes from a search.
Is it free?
Yes. There are no ads and nothing to sign up for, and the page works on any device.
The same hint in our game
Our sudoku game in Telegram explains a step on the board you are playing the same way, with new puzzles at six levels and a daily challenge.