Skip to content
Arctic Sudoku
← All techniques

Basic

Naked single

What it is

A cell has only one possible candidate left.

How to spot it

Look at an empty cell and list the digits already in its row, column and box. If eight different digits are taken, the ninth is the answer – with notes, it's a cell holding a single candidate.

Example

123123456789123456789
  • Basis
  • Removed / placed
r1c1 sees 1, 2, 3 and 4 in row 1, 5 and 6 in column 1, and 7 and 8 in its box. Only 9 is left, so r1c1 is 9.

Used from level: Easy