Naked Pairs
Short answer: a naked pair is two cells in the same unit that hold exactly the same two candidates and nothing else. Between them, those two cells must use up both shapes — so you can strike both shapes from every other cell in that row, column or box. It's the first real candidate-elimination move, the step up from singles.
What a naked pair looks like
Once singles dry up, pencil in the remaining candidates and look for two cells in one unit whose notes are an identical pair. Those two cells are locked together: whichever way round they go, they swallow both shapes — leaving no room for either shape anywhere else in the unit.
Nothing gets placed by this move — that's the shift from singles. A naked pair removes candidates, and those removals are what open up the next single somewhere else on the board.
How to use a naked pair
- Pencil in candidates. Naked pairs live in the pencil marks, so note the remaining shapes for the cells in a unit you want to work on.
- Find two cells with the same pair. Look for two cells in one row, column or box whose candidates are an identical two shapes — no more, no less.
- Lock the pair. Those two shapes are now reserved for those two cells: one takes the first shape, the other takes the second, in some order.
- Eliminate from the rest of the unit. Cross both shapes out of every other cell in that same unit. Each elimination may expose a new naked or hidden single.
A naked pair often comes before your next placement rather than being one itself. If the same idea appears with three cells and three shapes, you have a naked triple; the mirror image, where the shapes hide among other candidates, is a hidden pair.
Naked pair vs hidden pair
A naked pair is two cells whose only candidates are the pair — you spot it by the cells. A hidden pair is two shapes that can go in only two cells, even though those cells carry extra candidates too — you spot it by the shapes. Same logic, opposite viewpoint, just like naked and hidden singles.
Frequently asked questions
What is a naked pair in sudoku?
A naked pair is two cells in the same row, column or box that each have exactly the same two candidates and nothing else. Because those two cells must take those two shapes between them, the shapes can be eliminated from every other cell in that unit.
Does a naked pair place a shape?
Not directly. A naked pair removes candidates rather than filling a cell. Those removals often uncover a naked single or hidden single elsewhere, which is what you actually place.
Do the two cells need to be next to each other?
No. They only need to share a unit — the same row, the same column, or the same 3×3 box. As long as both cells hold exactly the same two candidates, the elimination works across the whole unit.
Do naked pairs work in normal number sudoku?
Yes, identically. Sudoku has no arithmetic, so the nine shapes behave exactly like the digits 1–9. A naked pair is the same deduction whether the symbols are numbers or the form9 shapes.