Naked Pair

Basic

Two cells in a unit share exactly two candidates; those digits are eliminated from all other cells in the unit.

How It Works

When exactly two cells in a unit (row, column, or box) share exactly the same two candidates (e.g. {3,7} and {3,7}), those two digits must occupy those two cells. Therefore 3 and 7 can be eliminated from all other cells in that unit.

This relies on the "locking" principle: two values occupy two cells.

Example

46
79
247
147
17
24
49
37
147
47
247
457
3
467
479
47
478
48
57
24
78
147
467
37
24
Key cells of the techniqueCells where elimination is appliedCandidate to be placedEliminated candidate (crossed out)

Row 4: R4C2={3,7}, R4C8={3,7} → 3 and 7 can be eliminated from all other cells in row 4.

Practice with a Real Puzzle

This 9×9 puzzle is solver-verified to require this technique on its solution path.

Easy32 givensStrict