Hidden Single
BasicUsed at: Beginner
A digit that can only go in one specific cell within its row, column, or box.
Hidden Single — Explained
A Hidden Single occurs when a specific digit can only go in one cell within its row, column, or box. While Naked Singles look at cells, Hidden Singles look at digits.
When to Use
Mid-game when Naked Singles alone aren't enough. Consciously scanning each digit's possible positions is key.
Common Mistakes
Focusing too much on one digit and missing other techniques. Move on after scanning all digits once.
Tips
Pick one digit and scan the entire board. Use placed numbers to narrow down where that digit can go.
Hidden Single Steps
Choose a digit
Pick a digit from 1 to 9 to scan for.
Scan units
Check where that digit can go in each row, column, and box.
Find the single cell
If a digit can only go in one cell within a unit, that's the answer.
Repeat for all digits
Check 1 through 9 in order. New ones appear as cells are filled.