Sudoku Rules

What is the goal of Sudoku?

Complete a 9×9 grid that is divided into nine 3×3 boxes. Some digits are given at the start. Fill the remaining cells so the completed grid follows all three rules at the same time.

The three essential rules

• Every row must contain digits 1 through 9 without repetition.
• Every column must contain digits 1 through 9 without repetition.
• Every 3×3 box must contain digits 1 through 9 without repetition.

Are diagonal numbers restricted?

Not in standard Sudoku. A diagonal may repeat a number unless the puzzle is specifically labelled as a diagonal variant. SudokuGG Classic uses the standard row, column and box rules.

Is Sudoku a maths puzzle?

No calculation is required. Digits could be replaced by nine different symbols and the logic would remain the same. Solving depends on location, elimination and recognising where a missing digit can fit.

How do you check a move?

Before entering a number, inspect its entire row, column and 3×3 box. If that number already appears in any of those units, it cannot be placed in the cell. If several values remain possible, add candidate notes and continue solving elsewhere.

Can a Sudoku have more than one solution?

A properly constructed standard puzzle should have one intended solution. The playable SudokuGG generators check their puzzle solution before presenting the grid.