Learn how Naked Pairs and Hidden Pairs work to eliminate candidate numbers and unblock challenging Sudoku puzzles.
A Naked Pair occurs when two cells within the same row, column, or 3x3 block contain the exact same two candidate numbers (for example, [1, 2]). Because those two numbers MUST occupy those two cells, neither number can appear anywhere else in that same unit. You can safely eliminate candidate numbers 1 and 2 from all other cells in that row, column, or block.
A Hidden Pair happens when two specific digits appear as candidates ONLY in the exact same two cells within a row, column, or block—even if those two cells contain other candidate numbers as well. Since those two digits must be placed in those two cells, all other candidate numbers in those two cells can be removed.
