Goal
Fill the grid so every row, column, and bold 3×3 box contains the numbers 1–9 exactly once.
Board Layout
- The board is a 9×9 grid, divided into nine 3×3 boxes.
- Some numbers are pre-filled as givens. Those never change.
- You fill the remaining empty cells with numbers 1–9.
Legal Moves
- You can place any number 1–9 into an empty cell.
- That number must not already appear in the same row, column, or 3×3 box.
- Givens are fixed and cannot be changed.
Sudoku is a logic puzzle. You can always solve it by reasoning about what fits.
How You Win
The puzzle is solved when every row, column, and box is complete with no repeats.
FFG Difficulty Levels
- Easy
- Medium
- Hard
- Expert
- Legendary
Technique Terms
You might see these terms in help, analytics, or future hints:
- Naked Single
- Hidden Single
- Locked Candidate
- Naked Pair
- Hidden Pair
- Naked Triple
- X-Wing
- Guess / Backtracking
Want a shorter version? See How to Play.