A state where only one candidate remains for a given cell. The most fundamental solving technique in Sudoku.

A Naked Single occurs when the constraints of the row, column, and block that a cell belongs to eliminate all but one possible digit. Puzzles at the Easy level can be solved entirely using this technique alone.

How to Find Them

List all digits present in the target cell's row, column, and block, then exclude them from 1-9. If only one candidate remains, that is a Naked Single. If two or more candidates remain, other techniques are needed.

Practical Tips

Naked Single is a "cell-focused" technique. Since you calculate candidates for each cell, it can be found mechanically using pencil marks. However, checking all 81 cells is time-consuming, so in practice you should prioritize intersections of rows, columns, and blocks that already have many digits filled in.