Hidden Pairs
When two digits can only go in the same two cells of a unit, those cells must hold that pair — clearing every other candidate from them.
When to use it
Use when two digits are restricted to the same two cells of a row, column or box, even if those cells also show other candidates.
Worked example
-
Two digits — here 4 and 7 — can only appear in these two cells of the row, hidden among other candidates.
-
Because the pair must fill those two cells, every other candidate is removed from them.
Common mistakes
- Confusing it with a naked pair: a naked pair shows only two candidates; a hidden pair hides behind extra ones.
- Checking only that the two digits sit in those cells, not that they are confined to them.
Frequently asked questions
What is a hidden pair in Sudoku?
Two digits that can only be placed in the same two cells of a unit. Those cells must take the pair, so their other candidates can be removed.