How to Spot Naked Singles
The Naked Single is the most basic technique, but it is surprisingly easy to miss. Learn the right approach to scan efficiently and fill in cells faster.
Cross-Hatching Method
The most efficient way to find Naked Singles is called cross-hatching. Focus on one number at a time and eliminate positions where it cannot go.
Pick one number to search for (start from 1)
Mark rows and columns where that number already appears
Within each 3×3 block, find empty cells that are not marked
If only one empty cell remains, that is the answer
Common Oversights
❌ Forgetting to check the block
→ Always check all three directions: row → column → block
❌ Overwhelmed by too many numbers
→ Focus on one number at a time. Scan the whole board 9 times to cover all numbers.
❌ Not updating after placing a number
→ Every filled cell changes its row, column, and block. Update your mental model.
Practice Tips
Start with Beginner-level puzzles and practice cross-hatching from 1 to 9 in order. With practice, you can scan one number in about 30 seconds.
Practice at Beginner Level