sudokly
Hard · Typical solve: 15 to 30 minutes

Hard Sudoku, Free Online

Real challenge. Pointing pairs and box-line reduction territory.

EasyMediumHardExpertEvil
Hard00:00✕ 0
About hard

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.