How to solve a sudoku
- Click a cell and type the clues from your puzzle. Arrow keys move around; 0 or Delete clears a cell. On a phone, tap a cell and use the number pad. Or paste the whole puzzle as 81 characters.
- Press Solve to fill in the rest. The answers appear in green, so you can tell them from your clues.
- Stuck on one step? Press Hint instead. It fills one cell and explains why that digit must go there.
Sudoku rules in one line
Fill the 9×9 grid so every row, every column and every 3×3 box has each digit from 1 to 9 exactly once. The digits already printed are the clues; a well-made puzzle has one answer you can reach by logic alone.
Solving it yourself with hints
The Hint button is for when you want to keep solving but are stuck. It fills one cell and names the rule:
- Naked single. Look at one empty cell. If its row, column and box together already contain eight different digits, the ninth must go there.
- Hidden single. Pick a digit and a row (or column, or box) that doesn’t have it yet. If every empty cell but one already sees that digit somewhere, it goes in the one that’s left.
Easy and medium puzzles can usually be finished with these two rules. Hard ones need techniques such as pairs, pointing and X-wings, which spot candidates to rule out. When no single is available, the hint says so and gives you the answer for the cell with the fewest options.
Keyboard
| Key | Does |
|---|---|
| Arrow keys | Move between cells |
| 1 to 9 | Fill the cell and move right |
| 0, Space, Delete | Clear the cell |
| Backspace | Clear and move left |
| Enter | Solve |
| Ctrl+V | Paste a whole puzzle |
| Ctrl+Z | Undo |