The Naked Single in Sudoku
The Naked Single is the simplest move in Sudoku and the one every solve ends on. When a cell has only one candidate left, that digit is forced — you can write it in straight away.
How to use Naked Singles, step by step
- Pencil in the candidates for each empty cell.
- Scan for any cell showing just one candidate.
- Write that digit in — it is the only one that fits.
- Remove that digit from the cell’s row, column and box.
- Repeat — each placement often creates the next Naked Single.
What is a Naked Single?
A Naked Single is a cell whose candidates have been whittled down to exactly one digit, so that digit must go there. It is “naked” because the single possibility is plain to see in the cell. Compare it with the hidden family, where you track where a digit can go rather than what a cell can be. The mirror move is the hidden single.
Naked Single vs Hidden Single
A Naked Single asks “what can this cell be?”; a Hidden Single asks “where can this digit go?”. Both place a digit with certainty, and most Easy and Medium grids are solved by these two alone. Beginners spot Naked Singles easily but miss Hidden Singles — learning both is the biggest early jump in speed.
Naked Single in Sudoku: FAQ
What is a Naked Single in Sudoku?
A Naked Single is a cell that has only one candidate digit remaining after eliminations, so that digit is forced into the cell. It is the most basic Sudoku technique.
How is a Naked Single different from a Hidden Single?
A Naked Single is a cell with a single possible digit. A Hidden Single is a digit that has only one possible cell in a row, column or box, even if that cell still shows other candidates.
Do you need pencil marks for Naked Singles?
On easy boards you can often see them by elimination, but pencil marks make Naked Singles obvious and are essential once the grid gets harder.