Sources and verification

The reference: the app

The rules described on this site are those of the Sudoku app, read from its code: number checking, end of the game, hints, entering a grid, settings. When the app's built-in help and its code differ, the site follows the code.

Sources consulted

• Sudoku (new tab) (Wikipedia, in French): the rules of the game, its vocabulary (cell, row, column, box, candidate) and its history.
• Mathématiques du sudoku (new tab) (Wikipedia, in French): the minimum number of given numbers in a grid with a unique solution.
• Mathematics of Sudoku (new tab) (Wikipedia): the computer proof of this minimum (McGuire, Tugemann and Civario, 2012).
• Sudoku solving algorithms (new tab) (Wikipedia): backtracking search, the method used by the app's solver, and constraint-based solving.

Links checked on October 30, 2026.

How the grids are verified

Before each publication, two independent programs redo all of the site's calculations:

• a tool connected to the app's engine, without modifying it, reads the 400 grids shipped with the app, counts their given numbers and asks the app's solver how many solutions each one has;
• it extracts the grids shown on the site, with their solution, and replays the construction of the screens used for the screenshots;
• a second program, written separately, reads the same grids from the app's code, checks each solution, recounts the solutions, finds each cell and each number of the techniques again, and blocks publication at the slightest discrepancy.

Found a mistake? Write to us via the contact page.