Sudoku Strategy: Hidden Singles
A Hidden Single is a number that must go in a cell — not because the cell has only one possibility, but because it's the only cell that can take that number in its row, column, or box.
How It Works
Let's say you're scanning a 3x3 box for where the number 2 could go. Even if multiple cells are empty, only one might logically allow a 2 without breaking the rules. That's a Hidden Single.
Example
In a row, you have 4 empty cells. After checking the other rows and boxes, you find only one of those can accept a 7. That's a Hidden Single — place the 7.
Tip
This is more about scanning rows/columns/boxes for missing numbers — not candidates per cell.
Practice Hidden Singles
Continue with Naked Pairs to boost your solving speed.