Naked Singles: The Foundation of Sudoku Solving
Learn the most fundamental Sudoku technique - finding cells with only one possible candidate.
The Naked Single technique is the most fundamental solving method in Sudoku. It occurs when a cell has only one possible candidate value remaining.
How It Works
When you've eliminated all but one candidate from a cell, that remaining candidate must be the solution for that cell. This happens when:
- Eight different numbers already appear in the same row
- Eight different numbers already appear in the same column
- Eight different numbers already appear in the same 3x3 box
Why It's Called "Naked"
The term "naked" in Sudoku means the information is immediately visible - you don't need complex logic to find it. The single remaining candidate is "naked" or exposed.
The word "naked" in Sudoku techniques refers to candidates that are obviously visible, as opposed to "hidden" techniques where the information requires deeper analysis to uncover.
When to Use This Technique
Always scan for naked singles after placing any number. They often appear as a chain reaction - placing one number can create new naked singles elsewhere on the grid.
Always scan for naked singles after placing any number - they often appear as a chain reaction!
Common Mistakes
- Forgetting to check all three constraints: Always verify the row, column, AND box before placing a number
- Not updating candidates: After placing a naked single, update candidates in all affected cells
- Rushing: Take time to systematically check each cell
Practice Tips
Start by filling in all obvious naked singles
Scan the entire grid and place any cells that clearly have only one possible value.
After each placement, scan affected regions
Check the row, column, and box where you just placed a number for new naked singles.
Work methodically
Move systematically from top to bottom, left to right to ensure you don't miss any.
Track candidates
Keep track of possible candidates mentally or write them in pencil for complex puzzles.
Next Steps
Once you've mastered naked singles, you're ready to learn about Hidden Singles - another beginner-friendly technique that complements this one perfectly.