Sudoku FlowNaked Single vs Hidden Single
The difference between a naked single and a hidden single in Sudoku, how to spot each one, and which to look for first.
Updated 2026-10-04
Naked single
Look at one empty cell. Rule out every digit that already appears in its row, its column and its box. If exactly one digit is left, that digit goes in the cell.
Hidden single
Pick one digit and one row, column or box. If the digit can go in only one empty cell of that unit, it goes there, whatever else that cell could hold.
The difference at a glance
| Naked single | Hidden single | |
|---|---|---|
| What you look at | One cell | One digit in one row, column or box |
| What you check | All nine digits against the cell's row, column and box | Every empty cell of the unit, for one digit |
| Other candidates in the cell | None left | Can be several |
| Level in our app | Easy | Medium |
Which to look for first
Without notes, hidden singles are usually easier to see: sweeping one digit across the grid needs nothing written down. With full notes, naked singles stand out, because the cell shows a single candidate.
Learn each technique
Practice
Every Find the Mistake puzzle on this site has exactly one wrong digit, and you can play each board right on its page.
