Sudoku365
Naked Singles Strategy
Naked Singles is the most fundamental Sudoku solving technique. It's the first strategy beginners learn and remains useful even in expert puzzles for finding obvious placements.
What is a Naked Single?
A Naked Single occurs when a cell can only contain one possible number based on the existing numbers in its row, column, and 3x3 box.
How to Identify Naked Singles
For each empty cell, check which numbers from 1-9 are already present in:
- The same row
- The same column
- The same 3x3 box
If only one number is missing from all three units, that's the number that must go in the cell.
Step-by-Step Example
Consider an empty cell in Row 1, Column 1:
- Row 1 contains: 2, 3, 4, 5, 6, 7, 8, 9
- Column 1 contains: 2, 3, 4, 5, 6, 7, 8
- Top-left box contains: 2, 3, 4, 5, 6, 7
The only number from 1-9 that doesn't appear in any of these units is 1. Therefore, that cell must be 1.
Tips for Finding Naked Singles Faster
- Start with cells that have many neighbors: Cells in boxes with lots of given numbers are easier to solve
- Process systematically: Go row by row, or box by box, rather than jumping randomly
- Look for almost-complete units: Rows, columns, or boxes with only one or two empty cells often yield naked singles
- Use elimination: For each cell, mentally cross off numbers that appear in the same row, column, and box
When Naked Singles Aren't Enough
Easy puzzles can often be solved using only Naked Singles. However, medium and harder puzzles will reach a point where no naked singles remain. At that point, you'll need to learn additional techniques like Hidden Singles and Naked Pairs.
Practice This Technique
The best way to master Naked Singles is through practice:
- Play an Easy puzzle - can often be solved with Naked Singles alone
- Try a Medium puzzle - uses Naked Singles as a foundation