Intermediate Technique

Hidden Pairs

Discover pairs of numbers that can only appear in two specific cells, even when other candidates are present.

What Are Hidden Pairs?

Hidden Pairs occur when two numbers can only be placed in two specific cells within a row, column, or 3x3 box, but these cells may contain other candidate numbers as well. Unlike Obvious Pairs, the pair is "hidden" among other candidates.

Key Point

When you find a Hidden Pair, you can eliminate all other candidates from those two cells, leaving only the pair numbers. This simplifies the puzzle and may reveal new solving opportunities.

How to Identify Hidden Pairs

The Process

  1. 1 Examine candidate possibilities in a row, column, or box
  2. 2 Look for two numbers that can only appear in exactly two cells
  3. 3 Verify no other cells in the group can contain these numbers
  4. 4 Remove all other candidates from those two cells

Hidden vs Obvious

The difference between Hidden and Obvious Pairs is visibility:

  • Obvious Pairs: Two cells each contain exactly two candidates
  • Hidden Pairs: Two numbers are restricted to two cells, but other candidates may be present

Hidden Pairs are harder to spot because you need to track where numbers can go, not just what's in each cell.

Example Walkthrough

Finding the Hidden Pair

Let's examine this row where we have a Hidden Pair. Numbers 1 and 2 can only appear in cells 4 and 6, even though these cells have other candidates:

5
6 79
3
12 4 8
46 89
12 5 7
456 79
456 89
456 78

Yellow cells contain the hidden pair (1,2). Other cells cannot contain 1 or 2.

After Eliminating Other Candidates

Since 1 and 2 must go in cells 4 and 6, we can remove all other candidates from those cells:

5
6 79
3
12
46 89
12
456 79
456 89
456 78

Candidates 4, 5, 7, and 8 have been eliminated from the pair cells.

Result

The two cells now form a cleaner pair that can help solve other cells. Even though we don't know which cell gets 1 and which gets 2, the elimination of other candidates often reveals new singles or pairs elsewhere.

When to Use Hidden Pairs

Best Scenarios

  • ✓ After basic techniques have been exhausted
  • ✓ When groups have multiple empty cells with complex candidates
  • ✓ As preparation for more advanced techniques
  • ✓ When candidate lists need simplification

Common Mistakes

  • ✗ Incomplete checking - verify numbers can't go elsewhere
  • ✗ Over-elimination - only remove from the pair cells
  • ✗ Confusing with obvious pairs
  • ✗ Forgetting to check all three groups

Practice Tips

How to Find Hidden Pairs

  1. 1 Choose a row, column, or box with 4-6 empty cells
  2. 2 Write down candidates for each empty cell
  3. 3 For each missing number, mark which cells it could go in
  4. 4 Look for pairs of numbers restricted to the same two cells

Related Techniques

Previous: Obvious Pairs Next: Pointing Pairs

Ready to Practice Hidden Pairs?

Try finding hidden pairs in your next puzzle - look for numbers restricted to just two cells!

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