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Hidden Pairs technique in Sudoku
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Hidden Pairs

Find the Pairs Hiding Among Other Candidates

By Minimal Sudoku TeamLast updated:

Hidden Pairs occur when two candidates appear in only two cells within a unit — but those cells also contain other candidates that "hide" the pair. Once found, you can eliminate all other candidates from those two cells.

Quick Summary
  • What: Two candidates that appear in exactly two cells within a unit
  • Why "hidden": The cells have other candidates that obscure the pair
  • Result: Remove all other candidates from those two cells
  • Difficulty: Intermediate — harder to spot than Naked Pairs

The Concept

In every row, column, or box, each digit must appear exactly once. If two specific digits can only go in the same two cells within a unit, those cells must contain those digits — nothing else.

The pair is "hidden" because the cells usually have other candidates too. The key insight is looking at where specific digits can go, not what's in the cells.

The Golden Rule

👀 Hidden Pair Rule
When two candidates appear in exactly two cells within a unit (and no other cells), those two cells must contain those two candidates. Eliminate all other candidates from those cells.

How to Find Hidden Pairs

1

Pick a unit to analyze

Choose a row, column, or box with several empty cells and candidates to examine.
2

Count candidate positions

For each missing digit (1-9), count how many cells in the unit can contain it.
3

Find digits with only 2 positions

Look for digits that can only appear in exactly 2 cells within the unit.
4

Find matching pairs

If two digits both appear in the exact same two cells (and only those cells), you've found a Hidden Pair!
5

Eliminate other candidates

Remove all other candidates from those two cells — they must contain the Hidden Pair digits.

Practical Example

Hidden Pair on 4 and 9

Hidden Pair example with candidates 4 and 9

In row 5, let's check where digits 4 and 9 can go:

  • Digit 4: Can only go in R5C3 or R5C7
  • Digit 9: Can only go in R5C3 or R5C7

Both digits are limited to the exact same two cells! These cells might also contain other candidates (like 2, 5, 8), but that doesn't matter.

Eliminations
Remove all candidates except 4 and 9 from R5C3 and R5C7. These cells must contain the 4-9 pair.

After elimination, the cells become a Naked Pair (4,9) — which may enable further eliminations!

Hidden Pairs vs Naked Pairs

These techniques are two sides of the same coin:

👥 Naked Pair

Two cells have only the same two candidates.

Eliminate those candidates from other cells in the unit.

👀 Hidden Pair

Two candidates appear only in the same two cells.

Eliminate other candidates from those cells.

They're Equivalent!
When you find a Hidden Pair and eliminate other candidates, the cells become a Naked Pair. The two techniques are mirror images — one looks at cells, the other looks at digits.
Naked PairsIntermediate

Naked Pairs

Learn the complementary technique that works from the opposite direction.

Hidden Triples & Quads

Like Naked Sets, Hidden Sets extend to larger groups:

Hidden Pair

2 digits in exactly 2 cells

Hidden Triple

3 digits in exactly 3 cells

Hidden Quad

4 digits in exactly 4 cells

Hidden Triples & QuadsIntermediate

Hidden Triples & Quads

Extend the Hidden Pair concept to find even more complex patterns.

Detection Tips

Focus on Rare Candidates
Digits that appear in only 2-3 cells within a unit are prime candidates for Hidden Pairs. Start your search there.
Use Process of Elimination
List which cells can contain each missing digit. When two digits share the exact same 2-cell list, you've found a Hidden Pair.
Snyder Notation Helps
Snyder Notation marks candidates when they can only go in 2 cells — exactly what you need to spot Hidden Pairs! If two Snyder marks (different digits) appear in the same two cells, that's a Hidden Pair.
Don't Forget the Result
Hidden Pairs eliminate candidates from the pair cells, not from other cells. This is the opposite of Naked Pairs!

Related Techniques

Hidden Sets Family

🔍Hidden Triples & Quads👥Naked Pairs

Related Techniques

✏️Snyder Notation👉Pointing Pairs✈️X-Wing