Two cells with the same two candidates lock those digits in place, clearing them from the rest of the unit.
Look for two cells in one unit whose candidate lists are identical and exactly two digits long. Those digits are then committed to those two cells, even though you cannot yet tell which goes where, so delete both from the rest of the row, column or box.
A Naked Pair occurs when two cells in the same unit (row, column, or box) each contain exactly the same two candidates, and no other candidates. We don't know which digit goes where yet, but we know for certain that these two digits will occupy these two cells. Therefore, both digits can be removed from all other cells in that unit.
The pair is called "naked" because the two candidates are fully visible. There's nothing else in the cells to obscure them. This is in contrast to a Hidden Pair, where the key digits are mixed in with other candidates.
Naked Pairs are one of the most satisfying techniques to spot. They appear regularly in Medium and Hard puzzles and often trigger a cascade of further eliminations.
The logic is elegant. If R4C2 has candidates {3, 7} and R4C8 also has candidates {3, 7}, then one of these cells must be 3 and the other must be 7. We can't tell which is which yet, but we know both digits are accounted for.
Since 3 and 7 are "claimed" by these two cells, no other cell in row 4 can contain 3 or 7. Remove 3 and 7 from the candidate lists of every other cell in row 4.
The same logic applies if the pair shares a column or a box instead of a row. And if two cells share both a row and a box (like R1C1 and R1C3, both in box 1), you can eliminate from both the row and the box.
Critical rule: both cells must have exactly these two candidates and nothing else. If one cell has {3, 5, 7} instead of {3, 7}, it's not a Naked Pair. The cell with three candidates could be 5, which would break the pair logic.
Example 1: Naked Pair in a Row
Look at row 1. After filling in pencil marks, two cells stand out: R1C3 has candidates {7, 9} and R1C6 also has candidates {7, 9}, and nothing else. This is a Naked Pair.
Since 7 and 9 must occupy R1C3 and R1C6 (in some order), neither digit can appear anywhere else in row 1. Scan the remaining empty cells.
Remove 7 and 9 from R1C7 and R1C9, and 9 from R1C8. After eliminating, R1C7 drops to a single candidate (6), a Naked Single. Place it and continue.
Example 2: Naked Pair in a Box
Now look at box 3 (top-right). R1C7 has candidates {4, 9} and R2C8 also has {4, 9}. These two cells form a Naked Pair within the box.
Since 4 and 9 are claimed by R1C7 and R2C8, remove both digits from all other empty cells in box 3: R1C9, R2C7, and R2C9.
After eliminating, R2C7 drops to a single candidate (6), a Naked Single. Notice how the pair cells don't need to share a row or column, they just need to share a unit.
Example 3: Naked Pair in a Column
In column 5, cells R5C5 and R7C5 both contain exactly {1, 8}. No other cell in column 5 has both of these candidates together. Since 1 and 8 must go in these two cells, eliminate 1 from R4C5 (which had {1, 3, 5}).
A Naked Pair's two cells contain those two candidates and nothing else, so the digits are fully visible. In a Hidden Pair the two digits appear in only two cells of the unit, but those cells carry extra candidates that obscure the pattern. Naked is about what the cells contain; hidden is about where the digits can go.
No. Both cells must show exactly those two candidates and nothing more. If one cell holds {3, 5, 7} while the other holds {3, 7}, the first cell could turn out to be 5, so the two digits are no longer guaranteed to occupy the two cells and the eliminations would be unsound.
No, and that is exactly what makes the technique work. Knowing the two digits fill the two cells in some order is enough: between them they use up both digits, so neither can appear anywhere else in the unit. Which cell takes which digit is settled later by other eliminations.
A Naked Pair works in any single unit, so a box is fine and the two cells need not be aligned. Pairs inside a box are the ones most often missed, precisely because they do not form a straight line. Wherever both cells share one unit, the eliminations apply across that unit.
Then eliminate from both units. Two cells such as R1C1 and R1C3 sit in row 1 and in box 1, so the pair's digits can be removed from the rest of the row and from the rest of the box. Check for that overlap every time, as it is easy to clear the row and forget the box.
Re-scan the units you changed. A Naked Pair's eliminations often leave another cell with a single candidate, or expose a further pair, so the technique tends to cascade. If nothing follows immediately, the shortened candidate lists still stand, and they give the next technique you try more to work with.
Explore all 28 solving techniques in our complete technique guide.