Difficulty · Evil
Evil Sudoku — Free Insanely Hard Puzzles
Evil is our hardest standard tier. Every puzzle strips down to the bare minimum starting clues and demands the full advanced toolkit — X-Wings, Swordfish, XY-Wings, and forcing chains.
17–22 starting clues — pared to the bone.
Guaranteed unique logical solution.
Verified time tracking on the Evil leaderboard.
Snyder notation makes chain-hunting practical.
The Evil toolkit
You'll cycle through pointing pairs, hidden pairs, X-Wing, Swordfish, and forcing chains on nearly every board. Study our advanced strategies guide before you start.
Beyond Evil
Once Evil feels routine, add the daily challenge and tournament modes for competitive verified times.
Frequently asked questions
What is Evil Sudoku?
Evil Sudoku is the highest standard difficulty tier. Puzzles start with 17–22 clues and require chains, X-Wings, and Swordfish to solve.
Is Evil Sudoku still solvable by logic?
Yes. Every SodokuDX Evil puzzle has exactly one solution reachable by pure logic. If you're guessing, there's a technique you haven't tried yet.
How long should Evil Sudoku take?
30–60 minutes is typical. Under 20 minutes is world-class.