Naked Single
A cell with one and only one possible digit. The easiest move in sudoku and the most common.
Beginner sudoku technique
What it is
A naked single is a cell whose row, column, and 3×3 box together have already used eight of the nine digits — leaving exactly one digit that can legally go there. Place it. Naked singles drive almost every easy-tier puzzle and continue to appear throughout medium and hard puzzles as the board fills in. Spotting them is the single most important skill to develop; every other technique exists to create more naked singles down the line.
Want the full theory?
The Naked Single guide on Sudoku247Wiki walks through the logic step by step, with worked examples, diagrams and FAQs.
Read the full Naked Single guide →Try it
The Sudoku247Online solver walks you through every move of any puzzle one logical step at a time, naming the technique that justifies each placement. Paste a puzzle to see this technique applied in real time.