Evil Sudoku Online

Evil sudoku is the hardest difficulty on Sudoku247. Each puzzle starts with the minimum 17 or 18 given numbers — the proven theoretical floor for a uniquely solvable 9×9 grid — and demands advanced techniques throughout. Expect to use X-wing, swordfish, naked triples, hidden pairs, and patient candidate chains; a guess-and-check approach won't get you far because every Evil puzzle is uniquely solvable, but the deductive path is buried deep. Sessions take real time. A confident expert-level solver who clears Expert in 8–10 minutes will routinely spend 30+ minutes on Evil. That's the point — these puzzles are for solvers who want a genuine cognitive workout, not a quick win. Every puzzle is freshly generated, so you'll never see the same board twice. Use Notes liberally, hit Show Candidates whenever you're stuck, and tier down to Master if Evil is wearing you out. If you finish one, you've earned the leaderboard XP bonus.