Techniques › Naked Pair
Naked Pair
Two cells in a house holding the same two candidates lock those digits away from the rest.
Two cells in the same house, each with exactly the same two candidates. You do not know which cell takes which digit — but between them they take both. No other cell in that house can be either digit.
A Naked Pair is the smallest example of a general idea that runs through the whole of sudoku: k cells holding exactly k digits between them own those digits outright. Triples and quads are the same argument with more cells.
A worked example
Taken from a real puzzle in our bank, at the point where this was the cheapest move available. Pattern candidates are marked in amber; anything the step eliminates is struck through in red.
| 5 | 1 | 4 | 2 | 38 | 38 | 6 | 9 | 7 |
| 8 | 3 | 7 | 5 | 69 | 69 | 2 | 4 | 1 |
| 9 | 6 | 2 | 1 | 7 | 4 | 5 | 3 | 8 |
| 1 | 9 | 6 | 4 | 5 | 38 | 38 | 7 | 2 |
| 3 | 7 | 5 | 689 | 2 | 689 | 89 | 1 | 4 |
| 2 | 4 | 8 | 39 | 1 | 7 | 39 | 6 | 5 |
| 6 | 2 | 9 | 7 | 4 | 5 | 1 | 8 | 3 |
| 4 | 5 | 3 | 89 | 89 | 1 | 7 | 2 | 6 |
| 7 | 8 | 1 | 36 | 36 | 2 | 4 | 5 | 9 |
- NudgeA few cells in column 6 share the same small set of candidates between them.
- WhereNaked Pair in column 6: r1c6, r4c6
- Do itRemove r5c6 ≠ 8
How to spot it
Look for two cells in a house with identical two-candidate lists. They do not have to be adjacent, only share a row, column or box.
Where you will meet it
Naked Pair sits at tier 1 of our ladder, which means it first becomes necessary at Easy. Puzzles below that band never require it, though it may still appear as a shortcut.
Read next
- Hidden Pair Two digits that can only go in the same two cells own them, whatever else those cells show.
- Naked Triple Three cells sharing three candidates between them lock those digits away.
- XY-Wing A pivot and two pincers. Whichever way the pivot falls, one pincer takes the digit.