Hard Sudoku
Hard puzzles usually need at least one advanced pattern — an X-Wing, a hidden triple, or a long chain of locked candidates. Fewer clues means more bookkeeping, so this is the level where a clean notes system matters most.
What to expect
- 240 puzzles in this level
- 26 clues on average
- Techniques: Naked Triple, Hidden Triple, X-Wing, Swordfish
- Average technique score: 122
Techniques in play
Frequently asked
What makes a sudoku "hard"?
In this rating, hard puzzles need Naked Triple, Hidden Triple, X-Wing and nothing harder. The label comes from the techniques a human solver is forced to use, not from the number of clues alone.
How long does a hard puzzle take?
Most players finish in 12–25 minutes. The timer pauses when you press Pause, and your progress is saved if you close the tab.
Do I need an account?
No. There is no sign-up, no email, and nothing leaves your browser. Progress is stored in localStorage on this device.
Are hints free?
Yes, all of them. A hint tells you which technique applies and why it works, then offers to place the digit — it does not just fill the cell.