The Complete Rules of Sudoku

The single rule for filling the 9×9 grid, plus the basic terms.

Sudoku is a logic puzzle where you fill a 9×9 grid with the numbers 1 through 9. There's only one rule: no number can repeat within any row, any column, or any of the nine 3×3 boxes.

The numbers provided at the start are called 'givens,' and from these alone, every remaining cell can be determined logically, one by one. A well-made puzzle has exactly one solution, so no guessing is needed.

Rows, columns, and boxes are collectively called 'units.' Any number already present in a cell's unit is excluded from that cell's candidates. This simple rule is the source of every solving technique.