Type in a puzzle, or take a photo of it, and press Solve step by step. The solver finds every move a person would make, from the first easy number to the last, using logic only. It names the technique of each step, highlights the squares that prove it and explains it in plain words, so you can follow along or stop at the step where you got stuck.
81 characters, row by row: 1 to 9 for numbers, 0 or a dot for empty squares. They load as puzzle numbers.
On each step, the solver looks for the easiest technique that places a number, the way a person would: a square with only one number left, a number with only one place in a row, column or box, then pairs, X-Wings, wings and chains. It is the hint engine of our app, so the steps and the words are the ones the app uses. It does not guess. Only a few of the hardest puzzles need a forcing chain, where one candidate is tried and followed until it breaks, and the solver says so when a step is one of those.
How the solver reads a photo, step by step →
The rating is the level of the hardest step, on the six levels of our app. These are the techniques that set each level:
What each Sudoku difficulty level asks of you →
Any classic 9 by 9 Sudoku with exactly one answer. If the numbers you type have no answer or more than one, it says so instead of guessing which one you meant.
Yes. Press Scan a photo and take a picture of the puzzle, or pick a screenshot. The photo is read on your device and never uploaded. Check the numbers it reads before you solve: the squares it is less sure of are marked.
The answer alone does not help with the next puzzle. Each step shows the pattern that made it possible, so next time you can spot it yourself. Show the solution is there when you only need the answer.
Yes, with no sign-up. It runs in your browser, so the puzzle you type stays on your device.
We also make a Sudoku app for iPhone, iPad, Mac and Android. There are no ads in it at all, it works offline, and when you ask for a hint it shows you the technique instead of just filling in a number.
Sudoku Flow is made by Rubigo Games, the developer of the Sudoku app recommended on this site.
Sudoku Flow