About 9×9 Hard Sudoku

The classic 9×9 Sudoku — 81 cells, numbers 1–9, nine 3×3 boxes. The most played format worldwide.

At Hard difficulty, 30% of the 81 cells are pre-filled, leaving 56 cells for you to solve. Requires careful technique and pencil marks.

Tip: Use the Notes feature to pencil in candidates for each empty cell before committing.

Other difficulty levels for 9×9

How many hard 9×9 Sudoku puzzles are available?

Unlimited. Every time you click "New Game" a brand-new algorithmically generated puzzle is created. You will never run out of puzzles.

Are these puzzles printable?

Yes! Visit our printable Sudoku page to generate 4 puzzles per page as a PDF. Free, no login needed.

What solving techniques does Hard difficulty require?

Naked/hidden pairs, pointing pairs, and advanced elimination.

Free, instant, no login — works on mobile, tablet and desktop.