🔥 Hard · 30 given numbers · ID hard-66
Hard Sudoku No. 66
A hard puzzle with exactly one solution. Techniques needed: naked single, hidden single, box/line reduction, x-wing, xy-wing.
The sheet below is exactly what prints on one A4 or Letter page. Choose “Save as PDF” in the print dialog if you prefer a file.
Keyboard: arrow keys to move, 1–9 to fill, Backspace to erase, N to switch notes.
Solution (hidden until you want it)
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About this puzzle
Hard puzzles require at least one advanced pattern: hidden pairs, naked or hidden triples, X-Wing or XY-Wing. Looking for a different challenge? Easy, Medium or Expert puzzles are on the printable Sudoku page.
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Try a hard riddle
Sudoku and riddles train the same muscle: spotting what must be true. Here are a few hard riddles with answers.