What is a hidden pair in sudoku?

A hidden pair is two digits that can only be placed in the same two cells of a row, column, or box, even though those two cells also list other candidates. Because those two digits have nowhere else to go in the unit, the two cells must hold them — so every other candidate can be erased from those two cells.

How is a hidden pair different from a naked pair?

A naked pair is two cells that contain only the same two candidates, so you erase those digits from the rest of the unit. A hidden pair is two digits confined to the same two cells (which also show other candidates), so you erase the other candidates from those two cells instead. Naked looks at the cells; hidden looks at the digits.

Why are hidden pairs hard to spot?

Because the pair is disguised. The two key cells look busy with several candidates, so nothing jumps out. You find hidden pairs by checking each unit for two digits that appear in only two cells — a digit-focused scan, not a cell-focused one.

Difficulty tier T2

Hidden Pairs in Sudoku: Find the Pair in the Clutter

The hidden pair is the naked pair's sneaky cousin. Same logic, but the pair is buried among other candidates, so you have to go looking for it by digit rather than by cell.

What a hidden pair is

Look at a unit — a row, column, or box. If two digits can each only be placed in the same two cells of that unit, those two cells form a hidden pair. It doesn't matter that the cells also list other candidates: since those two digits have nowhere else to go in the unit, the two cells are locked to holding them.

That lets you erase every other candidate from those two cells. Example: in a row, digits 4 and 9 can each only appear in cells A and B. Then A and B must be 4 and 9 in some order, so any other candidates in A and B are gone. Those eliminations usually expose a hidden single right after.

Hidden vs. naked — the mirror

Hidden pairs and naked pairs are two views of the same structure:

Pattern	You look at	What you erase
Naked pair	Two cells holding only two candidates	Those two digits, from the rest of the unit
Hidden pair	Two digits confined to the same two cells	Every other candidate, from those two cells

A naked pair announces itself — two clean cells. A hidden pair hides behind extra candidates, which is why it's the harder of the two to see.

Where it sits: hidden pairs are tier T2, alongside naked pairs and pointing pairs — the first level past pure singles. A puzzle that genuinely requires one is a step up from beginner. See techniques ranked by difficulty.

How to find them

Scan by digit, not by cell. For a unit, ask: which digits still have only two possible cells here? If two different digits share the same two cells, that's a hidden pair. This digit-first habit is the same one that finds hidden singles, so it folds naturally into a fast scanning routine.

Build the recognition with reps: practice free or take today's Daily Challenge.

Frequently asked questions

What is a hidden pair in sudoku?: A hidden pair is two digits that can only be placed in the same two cells of a row, column, or box, even though those two cells also list other candidates. Because those two digits have nowhere else to go in the unit, the two cells must hold them — so every other candidate can be erased from those two cells.
How is a hidden pair different from a naked pair?: A naked pair is two cells that contain only the same two candidates, so you erase those digits from the rest of the unit. A hidden pair is two digits confined to the same two cells (which also show other candidates), so you erase the other candidates from those two cells instead. Naked looks at the cells; hidden looks at the digits.
Why are hidden pairs hard to spot?: Because the pair is disguised. The two key cells look busy with several candidates, so nothing jumps out. You find hidden pairs by checking each unit for two digits that appear in only two cells — a digit-focused scan, not a cell-focused one.