Hidden Pairs
Rated 3.4 on the technique scale · Two digits, two cells.
A hidden pair is the mirror image of a naked pair: two digits that only appear in the same two cells of a unit. Those two cells must hold those two digits, so every other candidate in them can be removed.
Hidden pairs are easy to miss because the cells often look busy with four or five candidates. They are worth 3.4 points.
Hidden triples push the idea to three digits in three cells and are worth 4.0 points.
Hidden Pair — 4 and 6 only fit in these two cells of the row 4, so those cells hold nothing else.
Practice it: hidden pairs shows up most often in medium and hard puzzles. Browse those levels →
How the rating uses it
When a puzzle cannot be finished with easier techniques, the solver applies Hidden Pairs and adds 3.4 to the puzzle's score. The hardest technique a puzzle needs decides its level, and puzzles with 26 clues or fewer move up one level.