Expert Sudoku is built for solvers who already know the standard toolkit and want more. Swordfish, XY-Wings, unique rectangles and short chains are the everyday moves here; a puzzle can sit still for minutes until you spot the one link that breaks it open.
Every expert grid is rated 5.0–6.9 by Sudoku Explainer and has exactly one solution, so logic always wins over guesswork. Take your time, keep your notes accurate, and use undo freely. If you prefer variety, try the same level in expert Killer Sudoku.