Hidden Pair
A Sudoku solving technique · level 3 · first needed around SE grade 3
By The Hardest Sudoku Team · Last updated
TL;DR
A Hidden Pair is two digits that can only go in the same two cells of a unit, letting you strip all other candidates from those two cells.
How does the Hidden Pair work?
If two digits are each confined to the same pair of cells within a unit, those two cells must hold exactly those two digits — so every other candidate in those cells is eliminated.
When does it apply?
When two digits in a unit share an identical, exclusive pair of possible cells.
A worked example
If in a box only two cells can contain 2 or 5, then those cells are reduced to {2,5} and any other candidates there are removed.
See where this fits on the difficulty scale on the SE grade page, or browse every technique in the glossary.