Naked Pairs
A Naked Pair is one of the first advanced strategies sudoku players learn after mastering singles. It occurs when two cells in the same row, column or 3×3 box contain exactly the same two candidate digits — and no other candidates. Because those two digits are locked to those two cells, they can be safely removed from every other cell in that house, clearing the way for further deductions.
What is a naked pair?
Imagine you are scanning a row on your sudoku board, and you find two cells that each contain only the candidates {3, 7}. No matter which cell gets the 3 and which gets the 7, both digits are accounted for within those two cells. Therefore, no other cell in that same row can legally contain a 3 or a 7. You can erase those digits from the notes of every other cell in the row. The same logic applies to columns and 3×3 boxes. This elimination often reduces several cells from three or four candidates down to one or two — immediately revealing naked singles or creating new naked pairs.
Eliminate candidates
The key to spotting naked pairs on a sudoku board is having complete and accurate notes. Scan each house — row, column and box — and look for any two cells that display exactly the same two-digit candidate pattern. Once found, cross out those two digits from all other cells in that house. Do not be tempted to guess which cell gets which digit; the elimination alone is powerful enough. After removing the pair's digits, re-scan the affected cells for naked singles. A single naked pair often unlocks a chain of placements that breaks open an entire section of the sudoku puzzle.
Look for related patterns
The naked pair principle generalizes to larger sets: when N cells in one house share exactly the same set of N candidates, those N candidates are locked to those N cells. This leads to naked triplets, naked quads and even larger patterns. While naked pairs are common at the medium and hard sudoku levels, triplets and quads become essential at the expert and master difficulties. The discipline of keeping clean notes and systematically scanning for paired candidates is a habit that serves sudoku players from their first easy puzzle all the way to expert speed-solving. Every time you spot a naked pair, you are applying the same logical family that includes hidden pairs, pointing and claiming — the core of advanced sudoku strategy.