Hidden Pair
Two digits have only the same two homes in a unit. Every other note in those cells can go.
What it is
Start with two digits, not with two neat-looking cells. If both digits can appear only in the same two cells of one row, column or box, those two cells must hold them. Any other small digits written in those cells are only distractions and can be crossed out. You still do not know which of the two digits goes in which cell.
How to spot it
Stay in one row, column or box and follow one missing digit at a time. Notice the two cells where it can go. If a second digit points to exactly those same two cells, you have found a Hidden Pair. The cells can look messy because they often contain extra notes.
Worked example
One observation per step: find the two digits with just these two homes, then clear the extra notes.
Step 1 of 4: Look at one highlighted unit
Stay in this one row, column or box. Only the two highlighted note cells matter first.
Why it matters
A Hidden Pair clears crowded cells without guessing. Once the extra notes are gone, the pair is visible and may create the next useful move. It is a clean way to turn a busy unit into something you can read again.
Practise now
Solve a puzzle where this technique decides the game
Frequently asked questions
Why is it called hidden?
Because the two cells usually show several candidates, so nothing stands out visually. The pair only becomes apparent when you count where each digit can go.
What do I do after finding one?
Delete every other candidate from those two cells. The hidden pair then becomes a naked pair, which may allow further eliminations in the same unit.
How do I find hidden pairs faster?
Work digit by digit and note which cells could take each one. Digits with exactly two possible cells are worth comparing against each other.
Put it to use
Where you will meet it
Medium grids are where this move starts to matter: the obvious cells run out and the pattern takes over.
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