A naked single occurs when a cell has only one possible candidate.
Understanding the Concept
Also called "Sole Candidate" or "Forced Digit".
When all other digits 1-9 are eliminated from a cell, only one remains.
This happens when the cell's row, column, and box already contain 8 different digits.
The remaining digit must go in that cell.
Naked singles are easy to spot if you maintain candidate lists.
They're "naked" because the single candidate is obvious.
Examples
Naked Single at R4C4
R4C4 sees digits 1,2,3,4,6,7,8,9 in its row, column, and box. The only remaining possibility is 5 (shown in green).
5
3
7
6
1
9
5
9
8
6
8
6
3
4
8
123456789
3
1
7
2
6
6
2
8
4
1
9
5
8
7
9
Solution
Pro Tips
- •Keep candidates updated to spot naked singles
- •Check cells where many numbers see the cell
- •Naked singles often appear after placing other numbers
- •They're the logical result of elimination
