Sudoku

How it works

1
Import a photo of your grid (analyzed directly in your browser, nothing is sent) or generate a new one by choosing its difficulty (Easy, Medium, Hard).
2
Check the recognized digits, correct them if needed, then click "Validate the starting grid".
3
Use "Hint" for a step-by-step explained deduction, or "Solve the grid" to go faster.
4
"Check" at any time to spot a possible mistake, and use "Save game" / "Load a saved game" to resume later.

Import a photo of a grid Take a photo of a grid Load a saved game

Edit mode

The rules of the game

Sudoku is played on a 9x9 grid, divided into 9 blocks of 3x3. The goal: fill every cell with a digit from 1 to 9, without any digit repeating in the same row, the same column, or the same 3x3 block. The underlying idea traces back to the Latin squares studied by Swiss mathematician Leonhard Euler in the 18th century, but Sudoku in its current form appeared in the United States in the 1970s under the name "Number Place", before becoming hugely popular in Japan in the 1980s and then worldwide in the early 2000s.

Basic solving techniques

Hidden single: if a digit can only go in one cell of a row, column or block, it must go there, even if that cell still seems to have other possible candidates.
Direct elimination: for each empty cell, eliminate the digits already present in its row, column and block - what remains are the only possible candidates.
Pairs: if two cells in the same unit (row, column, block) share the exact same two possible candidates, those two digits can't be anywhere else in that unit - even without knowing which cell takes which digit.

Frequently asked questions

How does importing a grid from a photo work?

Take or import a photo of your grid: it's automatically straightened and each digit is recognized and placed in the grid. All that's left is to check and correct it if needed before solving or asking for hints.

What's the difference between "solve" and "hint"?

"Hint" shows you the next logical move to make, with an explanation of the technique used, so you can progress on your own. "Solve" completes the entire grid directly.