Sudoku for beginners: one rule is enough
No arithmetic and no guessing. Once you understand rows, columns and boxes, you are ready.
What are you trying to do?
A standard Sudoku is a 9×9 grid divided into nine 3×3 boxes. Fill the empty cells so every row, column and box contains the digits 1 through 9 exactly once.
The printed digits are clues and cannot be changed. A well-formed puzzle has one unique solution.
Look before you place
Start with a row, column or box that already contains many digits. Find what is missing, then use the crossing constraints to rule out impossible cells.
- Track one digit at a time
- Begin in the most crowded areas
- Write candidates instead of guessing
A reliable first routine
Scan boxes, then rows, then columns. Each placement creates new restrictions, so repeat the cycle. The puzzle opens one certain step at a time.
Try a row with two empty cells
Suppose a row reads 5, 3, _, 6, 7, 8, 9, 1, _. The missing digits are 2 and 4. That tells us the possibilities, but not their order. If the third column already contains a 4 elsewhere, the third cell cannot be 4: it must be 2. The last cell is then 4, provided its column and box allow it.
This is a local example, not a complete puzzle. Always check all three regions before entering a digit. Being absent from a row alone does not make a number correct.
Use the controls to practice, then check your reasoning
Select an empty cell and use the number keys or the on-screen keypad. Notes stores candidate digits; it does not commit an answer. Undo reverses your last move. A hint explains an available step before you choose to apply it.
For a first session, choose Easy and ignore the timer. Before each entry, say why every other digit is excluded. If you cannot explain a move, leave a note and inspect another region. Game progress is saved in this browser; a different device will not share it.