Difficulty
Beginner
This is where Naked Single normally sits in a human solving path.
Sudoku technique guide
Naked Single Sudoku Technique
A naked single is a cell with only one legal number left. This guide explains the idea in plain English, when to look for it, and the common mistake to avoid.
At a glance
Family
Basic Sudoku techniques
It belongs to the basic sudoku techniques group of Sudoku logic.
Main action
Usually remove candidates
Most technique moves reduce notes first. That often reveals a simpler placement afterwards.
What is Naked Single?
A naked single is a cell with only one legal number left.
The important thing is that this is logic, not guessing. You are using the current candidates to prove that a number must either go in one place, or cannot stay in another place.
In SudoSketch, this technique is designed to work with notes and Coach highlighting, so the key cells and removal cells can be shown clearly.
How Naked Single works
- Look at one empty cell.
- Check which numbers are blocked by its row, column and 3x3 box.
- If only one candidate remains, that number must go in the cell.
When to look for it
Look for Naked Single after easier moves have stopped working. First check for naked singles, hidden singles, locked candidates and simple pairs. If those do not move the puzzle forward, this technique may be worth checking.
For learning, do not try to scan for every advanced technique at once. Pick one method, understand the shape, and practise spotting that one pattern.
Common mistake
Do not place a number just because it looks likely. A naked single must have only one legal candidate left.
If you are unsure, rebuild the candidates first. Bad notes create bad logic, and Sudoku will absolutely punish you for it like a tiny spreadsheet goblin.
Naked Single FAQ
What is Naked Single in Sudoku?
A naked single is a cell with only one legal number left.
When should I look for Naked Single?
Look for Naked Single after simpler moves such as singles, locked candidates and obvious pairs have stopped helping.
Can SudoSketch Coach help with Naked Single?
Yes. SudoSketch Coach can highlight candidate patterns and explain the next logical step when a Naked Single move is available.