Play hard Sudoku online
Sparse. Expect to rule things out before anything falls.
Already have a game running at this grade? The same link picks it back up where you left it.
What a hard grid is like
Hard grids keep as few as 27 clues, and the generator checks that cracking one genuinely needs pattern work: naked and hidden pairs, triples, and the occasional X-wing. Long stretches pass with nothing obvious on the board, and then a single elimination unlocks a whole corner. Three hints per game, because a hint is worth more here than it is on an Easy grid.
| Clues kept | 27–32 of 81 |
|---|---|
| Hardest technique needed | Pairs, triples and X-wing |
| Hints per game | 3 |
| Mistakes allowed | 3 |
| Solutions | Exactly one, always |
A grade is two constraints, checked together. Clue count alone is a poor signal — a 30-clue grid can be trivial — so the generator also solves every candidate puzzle with a technique ladder and re-digs anything that comes out easier or harder than this grade promises.
How to approach it
Fill the notes in properly before you look for anything. On a hard grid the first real move usually comes from an elimination, not an observation, and you cannot see an elimination you have not written down.
Then look for pairs and triples: two squares in a unit sharing exactly two candidates lock those digits away from every other square in that unit. When that dries up, look along rows and columns for an X-wing — the same digit confined to the same two columns in two different rows removes it from those columns everywhere else.
Try another grade
- Easy Sudoku — Plenty of clues, and every square findable on its own.
- Medium Sudoku — Fewer clues, and units you have to read as a whole.
- Expert Sudoku — Very sparse. Long chains, and notes close to essential.
- Daily Challenge — one puzzle a day, the same grid for everyone.
New to the game? How to play covers the first few moves, the rules explain why there is always exactly one answer, and the strategy guide works through every technique named above.