Frequently Asked Questions About Sudoku
Short answers about rules, difficulty, Killer Sudoku, progress, and accounts.
Is Sudoku a math game?
No. Sudoku uses the digits 1–9, but you do not need arithmetic. The game is based on logical deduction and elimination.
Does every Sudoku puzzle need a unique solution?
A standard Sudoku puzzle should have exactly one solution. Puzzles in the game are checked before entering the playable library.
Which difficulty should beginners start with?
Start on Easy to get comfortable scanning rows, columns, and 3×3 blocks. When you solve consistently with few hints, move up to Medium.
What are Notes used for in Sudoku?
Notes let you record candidate digits that could fit a cell. They become especially important when the puzzle no longer has an obvious move.
How is Killer Sudoku different from Classic Sudoku?
Killer Sudoku keeps the row, column, and 3×3 block rules while adding cages with target sums and no repeated digits within a cage.
Can I continue a game after reloading the page?
Yes. Your in-progress game is saved in the browser. If you sign in, completed games and achievements are also synced to your player profile.