Hidden Pair

Interactive Tutorial

A Hidden Pair is the complement of a Naked Pair. When two digits can only appear in two cells within a unit, those cells must contain those digits. All other candidates can be eliminated from those two cells.

How It Works

The Mental Shift

Hidden pairs require digit-focused thinking — the opposite of naked pairs:

Approach Question Technique
Cell-focused "What candidates does this cell have?" Naked Pair
Digit-focused "Where can this digit go in this unit?" Hidden Pair

The Pattern

Look for two digits in a row, column, or box where:

The Logic

If only R1C8 and R1C9 can contain {6, 7} in Row 1, then:

The pair is "hidden" because the cells may contain many other candidates that obscure the pattern.

How to Spot Hidden Pairs

Step-by-Step Scanning

  1. Pick a unit — Choose a row, column, or box to scan
  2. For each digit, ask: "Where can this digit go?"
  3. Count positions — If a digit can only go in two cells, note them
  4. Find matching pairs — Two digits confined to the same two cells = Hidden Pair

Using Focus Mode

Focus Mode makes hidden pairs much easier to spot:

  1. Tap a digit to highlight all cells containing it
  2. Look for digits that appear in only two cells within a unit
  3. Check if another digit shares the same two cells

Example

Look at Row 1 and ask: where can each digit go?

Row 1 Analysis:

Both 6 and 7 are confined to the same two cells — this is a Hidden Pair!

Since R1C8 and R1C9 must contain 6 and 7, we can eliminate all other candidates from these cells.

Before: R1C8 has {2, 3, 4, 5, 6, 7, 9}, R1C9 has {3, 4, 5, 6, 7, 9}

After: R1C8 has {6, 7}, R1C9 has {6, 7} — now it's a Naked Pair!

puzzle: S9B4L49157P8982BUB4B20949040615074I1412100706088804018886031O090724011608223H1P087O988Y0396971N050J038Q08078Q024ABI0705B60206017Y1V8J0Z04AB03029U085PCH157NDV8I8AA6A6
mode: guided
technique: Hidden Pair
initial:
  layers:
    hints: true
steps:
  - text: >
      Where can 6 go in Row 1? Use Focus Mode to highlight all 6s.
    hint: subtle
    technique: HP
    state:
      focus:
        enabled: true
        digits: [6]

  - text: >
      Digit 6 only appears in R1C8 and R1C9. Now let's check digit 7.
    hint: subtle
    technique: HP
    state:
      selection:
        cells: [R1C8, R1C9]
      focus:
        enabled: true
        digits: [6]

  - text: >
      Digit 7 also only appears in R1C8 and R1C9 — the same two cells!
    hint: obvious
    technique: HP
    state:
      selection:
        cells: [R1C8, R1C9]
      focus:
        enabled: true
        digits: [6, 7]

  - text: >
      These cells must contain 6 and 7. Remove all other candidates: {2,3,4,5,9} from R1C8 and {3,4,5,9} from R1C9.
    hint: detailed
    technique: HP
    state:
      selection:
        cells: [R1C8, R1C9]
      focus:
        enabled: true
        digits: [6, 7]
settings:
  showCandidates: true
  showControls: true
  showDescription: true
  navigation: numbered

Hidden vs Naked

Both techniques achieve the same result — they lock two digits to two cells. The difference is perspective:

Aspect Naked Pair Hidden Pair
What you see Two cells with only two candidates Two candidates confined to two cells
Other candidates None in the pair cells Many others cluttering the cells
Elimination target Other cells in the unit The pair cells themselves
After elimination Other cells simplified Pair cells become a Naked Pair

Pro tip: After finding a Hidden Pair and eliminating, you've created a Naked Pair! This often triggers chain reactions.

Tips

  1. Use Focus Mode — Highlight one digit at a time to see where it can go
  2. Count systematically — For each digit, count its possible positions in the unit
  3. Look for "orphan" digits — Digits appearing in only two cells are your targets
  4. Check all units — Hidden pairs can appear in rows, columns, or boxes
  5. Expect clutter — Unlike naked pairs, the cells will have extra candidates hiding the pattern

Common Mistakes

More Puzzles

Related Techniques