Naked Single
BasicUsed at: Beginner
A cell with only one candidate remaining. The most basic technique.
Naked Single — Explained
A Naked Single occurs when a cell has only one possible digit remaining. This is the most fundamental Sudoku technique and the first one beginners should master.
When to Use
Early to middle game of beginner and easy puzzles. In hint-rich puzzles, this technique alone can take you all the way through.
Common Mistakes
Only checking the row and column while forgetting the box. Always verify all three directions.
Tips
Cross-hatch numbers 1 through 9 in order. New Naked Singles appear as other cells are filled.
Naked Single Steps
Pick an empty cell
Choose a cell that hasn't been filled yet.
Check the row
Look at numbers already in the same row and exclude them.
Check the column
Similarly exclude numbers from the same column.
Check the box
Exclude numbers from the same 3×3 box. If only one remains, that's the answer.