Naked Pair
A Naked Pair is two cells in the same unit that have exactly the same two candidates. The two digits must share these cells between them, so they can be removed from the rest of the unit.
See the technique in practice
Work through the examples step by step. Each step explains what you see in the puzzle and why the conclusion is valid.
- We add candidate notes to every empty cell in the puzzle to see which digits are still possible. Now we take a closer look at column 2.
How to recognize the pattern
A Naked Pair consists of two cells in the same unit with exactly the same two candidates, no more and no fewer. With candidate notes enabled, look for two identical two-digit sets in the same row, column or box. The two digits must occupy those two cells, so no other cell in the unit can contain them.
The pair itself does not directly solve any cells. The value lies in the eliminations: when the two digits disappear from the rest of the unit, new Singles or new Pairs often appear in the cells that lost candidates.
Step-by-step procedure
- Write candidate notes for all empty cells in the unit you are examining.
- Look for two cells that have exactly the same two candidates.
- Remove the two digits from all other cells in the same unit.
- Check whether the pair also shares another unit, because a pair in the same box and same row gives eliminations in both places.
- Look for new Singles in the cells that just lost candidates.
Common mistakes
- Accepting a cell with three candidates. Both cells must have exactly the two digits, or the logic does not hold.
- Removing from the wrong cells. The eliminations apply only to the unit the pair shares, not all neighbors of the two cells.
- Forgetting that the pair can lie in two units at once. Two cells in the same box can also share a row or column, and then the eliminations apply in both units.
When do you need the technique?
At the Medium level, placing digits directly is no longer enough. The focus shifts to eliminating candidates: when you can prove that a digit cannot go in a cell, the rest of the puzzle becomes easier. Add candidate notes, as they are essential to every technique from this point on.