Home › Hard Sudoku
Hard Sudoku
For solvers who want a real fight. Hard puzzles hold back their clues, so single-cell logic only gets you so far. You'll need pairs and chains to break these open.
Play Hard Sudoku free →What makes a Sudoku "hard"?
On Playoku, difficulty is graded by the hardest technique a puzzle actually requires, not by how few clues it has. A hard board will stall your naked and hidden singles and force you into naked pairs and pointing pairs to make progress.
- Freshly generated hard puzzles every game, each with one logical solution.
- Pencil notes are essential here: toggle notes mode and track every candidate.
- Undo, redo and hints when a line of reasoning runs dry.
- Auto-save keeps a tough board waiting for you, and it's all free.
Sharpen your technique
Our Sudoku tips & strategies guide covers exactly the moves hard puzzles demand: naked pairs, pointing pairs and the X-Wing. Want an even steeper climb? Try Expert Sudoku. Prefer to warm up first? Drop to Medium or Easy.
Frequently asked questions
What makes a Sudoku hard?
On Playoku a puzzle is graded by the hardest technique it actually requires, not by clue count. A hard board stalls simple singles and forces you into naked pairs and pointing pairs to break through.
Do hard Sudoku puzzles require guessing?
No. Every hard board has exactly one solution reachable by pure logic. If you are stuck, a valid deduction is always waiting — or drop the grid into the solver to see the next step.
What techniques do I need for hard Sudoku?
Beyond singles, you will lean on naked pairs, pointing pairs and sometimes the X-Wing. Keeping accurate pencil notes is what makes those patterns visible.