Difficulty
Hard
This is where Naked Quad normally sits in a human solving path.
Sudoku technique guide
Naked Quad Sudoku Technique
A naked quad is four cells in one area that reserve four candidates between them. This guide explains the idea in plain English, when to look for it, and the common mistake to avoid.
At a glance
Family
Subset techniques
It belongs to the subset 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 Quad?
A naked quad is four cells in one area that reserve four candidates between them.
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 Quad works
- Find four cells in one area.
- Together they use only four candidates.
- Those four candidates are reserved, so remove them from other cells in that area.
When to look for it
Look for Naked Quad 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
The four cells must be in the same area and together use only four candidates.
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 Quad FAQ
What is Naked Quad in Sudoku?
A naked quad is four cells in one area that reserve four candidates between them.
When should I look for Naked Quad?
Look for Naked Quad after simpler moves such as singles, locked candidates and obvious pairs have stopped helping.
Can SudoSketch Coach help with Naked Quad?
Yes. SudoSketch Coach can highlight candidate patterns and explain the next logical step when a Naked Quad move is available.