The intuition
If a row has two empty cells that both refuse every digit except, say, 4 and 8, then between them they must take exactly the values 4 and 8 — there's no other option. So 4 and 8 belong to those two cells alone; no other cell in the row is allowed to host them. Naked Pairs don't directly place digits, but they slash candidate lists and almost always trigger a wave of Hidden Singles on the next pass.
When you'll use it
Naked Pairs are the bridge from beginner to intermediate Sudoku. They appear regularly in Medium and Hard boards, and most stalled Medium puzzles break the moment you find one. Once you're fluent with the Hidden Single, this is the next technique to master.
How to spot a Naked Pair
- Pencil-mark candidates into the empty cells of one unit (row, column, or box).
- Scan for two cells whose candidate lists are both exactly the same pair — e.g. {3, 7} and {3, 7}.
- Those two digits must go into those two cells, in some order.
- Remove both digits from every other cell of that same unit.
Why the Naked Pair logic works
If only digits 3 and 7 can occupy two specific cells of a row, then 3 and 7 must collectively occupy those two cells (because each digit must appear once in the row, and there are only two places for them). Any third cell in the same row that previously listed 3 or 7 as a candidate can safely drop it — the row's quota of 3s and 7s is already booked.
A worked Naked Pair example
If R5C2 = {4, 8} and R5C7 = {4, 8}, then no other cell in row 5 can be 4 or 8. The pencil marks for 4 and 8 vanish from R5C3, R5C5, R5C8 — and a Hidden Single is usually waiting in line behind them.
Walkthrough
R5C2 and R5C7 both have exactly two candidates: {4, 8}. That's the trigger.
Because each cell can be only 4 or 8, and the row must contain one 4 and one 8, those two values are locked into those two cells. Some pair of (R5C2, R5C7) values must be (4, 8) or (8, 4).
Therefore no other cell in row 5 can hold 4 or 8. The pencil marks shown in R5C3 ({1, 2}) and R5C5 ({1, 2, 5}) and R5C8 ({2, 5}) — already free of 4 and 8 — confirm the elimination has been applied.
After the elimination, R5C5 has candidates {1, 2, 5} and R5C8 has {2, 5}. If one of the columns then forbids 1 or 5 in those cells (a typical chain reaction in Medium puzzles), a Naked Single appears immediately.
How to drill this technique
Generate a Medium puzzle, pencil-mark every empty cell with its candidates, and time yourself spotting the first Naked Pair. Repeat for ten puzzles. Most players go from two minutes to under twenty seconds in a week.
Common mistakes
- Spotting two cells with overlapping candidates and treating them as a pair. The candidate lists must match exactly — {3, 7} and {3, 5, 7} is not a Naked Pair.
- Eliminating outside the shared unit. A Naked Pair in a row eliminates only from that row, not from any column or box that happens to intersect.
- Skipping pencil-marking. Naked Pairs are almost impossible to spot without an accurate candidate grid.
FAQ
Is a Naked Pair the same as a Hidden Pair in Sudoku?
No. A Naked Pair is two cells whose candidate lists are both exactly the same two digits. A Hidden Pair is two digits that are only possible in the same two cells of a unit — even though those two cells may also carry many other candidates that the technique then eliminates. They're mirror images of each other.
Do Naked Pairs work in 3×3 boxes too?
Yes. The Naked Pair rule applies inside any unit — row, column, or 3×3 box. The elimination only affects the cells of that same unit.
Why didn't my Naked Pair solve anything?
Naked Pairs rarely place a digit directly. They eliminate candidates, which then exposes Hidden Singles or further Naked Pairs. After spotting one, re-scan the unit for Hidden Singles — that's almost always where the breakthrough is.
What about Naked Triples and Naked Quads — same idea?
Exactly the same idea, scaled up. A Naked Triple is three cells in one unit whose candidate lists together use only three digits — for example {2,5}, {2,7}, {5,7}. Those three digits are locked into those three cells. Naked Quads are the four-cell version and are rare outside Expert puzzles.
Is a Naked Pair stronger than a Hidden Single?
Neither is strictly 'stronger' — they answer different questions. A Hidden Single immediately places a digit; a Naked Pair only trims candidates. In practice you'll alternate between the two: a Naked Pair clears noise, the next Hidden Single becomes visible, and the puzzle moves forward.
What to learn next
Once Naked Pair feels natural, move on to Hidden Pair — it builds directly on the candidate-tracking habits you've just developed. Or revisit the full Sudoku techniques library to see the full progression from beginner to advanced.