Hidden Pairs - A Cleaner View of Tougher Sudoku
Hidden pairs are the quieter cousin of naked pairs. Instead of seeing two neat cells that both show the same two candidates, you scan a row, column, or box and notice that two particular digits can only live in the same two cells. The cells may contain extra notes, but those extra candidates are noise and can be removed.
This technique matters because it simplifies the grid without placing a number immediately. That simplification can unlock fresh singles, stronger pair logic, or a Pointing Pair soon after.
How to Spot a Hidden Pair
Pick one unit and examine candidate frequency. If digit 3 appears in only two cells and digit 9 also appears in exactly those same two cells, then 3 and 9 form a hidden pair there. Even if both cells also contain 1 or 6 as notes, those extra digits can now be removed.
The logic is simple: 3 and 9 must occupy those two cells somehow, so nothing else can stay there.
Why Hidden Pairs Matter
Hidden pairs reduce clutter. When candidate lists shrink, other techniques become easier to see. In Hard Sudoku, this cleaning step is often what reveals the next real breakthrough.
Frequently Asked Questions
What is a hidden pair in sudoku?
Two digits are restricted to the same two cells inside one unit, allowing other candidates in those cells to be removed.
How is it different from a naked pair?
A naked pair is visible directly in the two cells. A hidden pair must be found by scanning the whole unit.
When do hidden pairs appear?
They usually appear in challenging and hard puzzles after some earlier eliminations.
Next Steps
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