What hard sudoku feels like.
Hard sudoku starts with 28 to 31 clues. Singles run out fast and you will need pointing pairs, box-line reduction and occasionally an X-wing. Expect to spend most of the puzzle in pencil-mark mode.
- Typical solve time
- 15 to 30 minutes
- Who it's for
- Experienced players ready for intermediate techniques.
- Techniques
- Pointing pairs, Box-line reduction, Naked and hidden triples, X-wing
Hard sudoku FAQ
What techniques do I need for hard sudoku?
Beyond singles and pairs, you will usually need pointing pairs (a candidate that is confined to one row or column within a box, eliminating it from the rest of that row or column outside the box) and box-line reduction.
How long does hard sudoku take?
Plan for 15 to 30 minutes. Speed depends mostly on how quickly you spot pointing pairs and triples.
Why am I stuck even with full pencil marks?
You probably need a chain technique. Look for pointing pairs first. They are the most common unblocking move. If those do not help, try X-wing on a recurring digit.
Can hard sudoku always be solved with logic?
Yes. Every Sudokly hard sudoku is solvable with techniques up through X-wing. You should never need to guess.
Is hard sudoku good practice for expert?
Yes. Spending a few weeks on hard puzzles builds the pattern recognition you will need for expert and evil. Do not rush. Pattern fluency beats raw speed.