Hidden Pair
Two digits that can only appear in the same two cells of a house, disguised by extra candidates. Those extras can be stripped away.
Row 6 has four empty cells left, each with a few candidates.
How to spot it
- 1Find two digits whose only homes in a house are the same two cells.
- 2Those cells must take those two digits between them.
- 3Delete all other candidates from that pair of cells.
When to use
When a house looks candidate-heavy but two digits are quietly restricted.
Common mistake
Overlooking them entirely — hidden pairs wear a disguise of surplus candidates.
Worked Example
Look at a row with four empty cells left. After listing candidates: one cell shows {1, 3, 8}, another shows {1, 2, 8}, and the last two both show {2, 3}. Scan the row for where 1 and 8 could go — only those first two cells allow either digit; nowhere else in the row can take a 1 or an 8.
That means those two cells must hold 1 and 8 between them, in some order, even though each currently shows an extra candidate (a 3 in one, a 2 in the other). Since 1 and 8 have to go in those two cells, nothing else can — so the extra candidates come off, leaving just {1, 8} in both. The pair was "hidden" because it was buried under other candidates until you checked where each digit could actually go.