Hard Sudoku
Fewer given numbers, longer chains of deduction — 9×9 grids that make you work.
How to play
- Fill the grid so every row, column and 3×3 box contains 1 to 9, with no repeats.
- Tap Notes and pencil in candidates — at this level, keeping track of them is most of the work.
- Repeated numbers are highlighted gently and there is no game over, so you can follow a line and erase it if it dead-ends.
- The Hint explains the next simple step whenever one exists — the rest is yours to find.
What it trains
- Real deduction — the easy scans run out and you have to work with candidates
- Exactly one solution in every grid, with pencil marks built in for tracking them
- No ads, no account and no clock — leave a puzzle half-done and come back to it
Free hard sudoku online: each 9×9 grid starts with far fewer numbers than an easy one, so the obvious moves run out quickly and you have to track candidates to get anywhere. Every puzzle still has exactly one solution. Pencil marks are built in for precisely this, along with large-print mode and a teaching hint for the simpler steps. No ads, no account and no sign-up — and no timer and no game over, so a hard grid can sit half-finished until you come back to it. Step up to expert on the same page when hard stops biting. Plays on phone, tablet or computer.
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