Hard Sudoku
A serious challenge for experienced solvers. Hard puzzles have fewer givens and require advanced techniques: naked/hidden pairs, pointing pairs, and occasionally X-wings or swordfish patterns.
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What techniques do hard Sudoku puzzles require?
Hard Sudoku typically needs naked and hidden subsets (pairs, triples), pointing candidates, and sometimes more advanced patterns like X-wings. The conflict highlight in this puzzle helps spot contradictions when testing candidate chains.
About Sudoku
Sudoku is the timeless number-placement puzzle. Fill the 9x9 grid so every row, column, and 3x3 box contains each digit from 1 to 9 exactly once. Easy, medium, and hard puzzles — generated fresh every time. Free to play online.