Sudoku
Classic 9×9 Sudoku with four difficulty levels
Leaderboard
Free Sudoku online
PuzzleHub Sudoku generates valid puzzles with a unique solution. Pick Easy through Expert, use notes and hints, and track time and mistakes.
How to play Sudoku
Sudoku is a 9×9 logic puzzle. Fill the grid with digits 1–9 so that each digit appears once in every row, column and 3×3 block.
Step by step
- 1Select a cell and enter a digit from 1–9.
- 2Check the row, column and 3×3 block together: a value must be valid in all three areas.
- 3Use notes for candidates when a value cannot yet be determined directly.
- 4The hint searches for a strongly constrained cell and explains why the value fits.
- 5Time, mistakes and hints are included in your statistics.
Rules
- Each row contains digits 1–9 without duplicates.
- Each column contains digits 1–9 without duplicates.
- Each 3×3 block contains digits 1–9 without duplicates.
- A filled cell must satisfy all three constraints at the same time.
FAQ
How do I know which digit to place?
Start with rows, columns or blocks that have very few empty cells. List candidates for a cell and remove values already used in its row, column or block. If one candidate remains, the move is forced.
What are notes for?
Notes store several candidates without changing the main grid. When another cell is solved, you can remove candidates that are no longer possible.
What does the hint actually do?
The hint selects a cell with very few candidates or a single candidate and explains which constraints eliminate the other options.
Can I play with a keyboard?
Yes. Arrow keys move the selection, number keys enter values, and Backspace/Delete clears a cell.
Is unfinished progress saved?
Yes. The current game state and timer are stored locally in the browser so you can return later.
What happens after a mistake?
The puzzle remains playable. The mistake is counted in your statistics, and you can correct the cell and continue.
What happens when I finish the puzzle?
A result screen shows your time and statistics. You can start a new puzzle or choose another difficulty.