Naked Pairs: The First Advanced Technique Worth Learning
Sudoku a Day Blog
If you have been solving easy puzzles comfortably and medium puzzles feel like a wall, naked pairs might be the technique that gets you through. It is the first "advanced" method most solvers learn, and it is simpler than it sounds.
What is a naked pair?
A naked pair occurs when two cells in the same row, column, or box contain exactly the same two candidates and nothing else. For example, two cells that both show only {3, 7} as possibilities.
When this happens, you know that 3 and 7 must go in those two cells (one in each). That means no other cell in that same row, column, or box can contain 3 or 7. You can safely eliminate those numbers from all other cells in the unit.
For a deeper visual walkthrough, see our full naked pairs guide.
Why naked pairs matter
Scanning and naked singles work by finding cells with one possible value. But on medium and harder puzzles, you often reach a point where every unsolved cell has two or more candidates. Progress stalls.
Naked pairs break that stall by eliminating candidates from other cells, which can reduce those cells to singles. One pair elimination can cascade into three or four new placements. That is why this technique feels so satisfying when it clicks.
How to spot them
1. Pencil mark everything. Naked pairs are invisible without candidate notes. Mark all unsolved cells in the region you are working on.
2. Look for twin cells. Scan each row, column, and box for two cells with identical two-candidate pairs. They will have exactly the same two numbers and nothing else.
3. Eliminate from neighbors. Once you find the pair, remove both numbers from all other cells in that same unit (row, column, or box).
4. Check for new singles. After elimination, some cells may now have only one candidate. Place those immediately.
A concrete example
Suppose row 5 has three unsolved cells with these candidates: - Cell A: {2, 8} - Cell B: {2, 5, 8} - Cell C: {2, 8}
Cells A and C form a naked pair: both contain only {2, 8}. That means 2 and 8 are locked into those two cells. Cell B cannot be 2 or 8, so it must be 5.
One pair, one immediate placement. That is the power of this technique.
Common mistakes with naked pairs
Confusing naked pairs with hidden pairs. A naked pair has exactly two candidates and nothing else. A hidden pair is when two numbers appear in only two cells within a unit, but those cells may have other candidates too. Both are useful, but they require different scanning approaches.
Forgetting to check all three unit types. A naked pair can appear in a row, a column, or a box. Check all three when you are searching.
Not updating marks after elimination. After removing candidates, re-scan the affected cells. Stale marks hide follow-up opportunities.
Beyond pairs
Once you are comfortable with naked pairs, the same logic extends to triples and quads. Three cells with the same three candidates form a naked triple. The elimination principle is identical, just applied to larger groups.
But start with pairs. They are the most common and the easiest to spot. Master them, and medium puzzles will feel significantly more approachable.
When to look for naked pairs
The best time to hunt for pairs is after your initial scanning pass, when obvious singles are exhausted and progress has slowed. If you have pencil marks written and no cell has a single candidate, that is your signal to start checking for pairs.
Focus on the most crowded rows or boxes first. Pairs tend to appear where candidates are densely packed, because dense regions have more constraint interactions.
Practice spotting pairs on today's medium daily puzzle or download a printable medium pack.
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