Naked Single
Rated 2.0 on the technique scale · A cell with one candidate left.
A naked single is the simplest deduction in sudoku: a cell that has exactly one digit which does not already appear in its row, column or box.
Beginners often scan by digit instead. Both work, but singles are the foundation — every other technique eventually hands you a single to place.
In Sudoku Atelier, a naked single is worth 2.0 points on the rating scale, which keeps easy puzzles easy even when they need a hundred of them.
Naked Single — Row 3, column 2 already sees all eight other digits in its row, column and box, so it can only be 9.
Practice it: naked single shows up most often in easy and medium puzzles. Browse those levels →
How the rating uses it
When a puzzle cannot be finished with easier techniques, the solver applies Naked Single and adds 2.0 to the puzzle's score. The hardest technique a puzzle needs decides its level, and puzzles with 26 clues or fewer move up one level.