Sudoku Guide, Rules, and Tips
Sudoku is a logic puzzle on a 9×9 grid divided into nine 3×3 boxes. Fill in the empty cells so that every row, column, and box contains the digits 1 to 9 exactly once. No arithmetic is required; every well-made puzzle has a single solution that can be reached by pure deduction.
How to Play
- Each row must contain the digits 1–9 with no repeats.
- Each column must contain the digits 1–9 with no repeats.
- Each 3×3 box must contain the digits 1–9 with no repeats.
- The given clues cannot be changed. The puzzle is solved when every cell is filled correctly.
Strategy and Tips
- Start with naked singles: cells where only one digit is possible after checking the row, column, and box.
- Scan each box for hidden singles, where a digit can go in only one cell.
- Pencil in candidates on harder puzzles so you can spot pairs and eliminate options.
- Never guess. If you are stuck, look for a row, column, or box with the fewest empty cells.
Controls
Select a cell with the mouse or a tap, then enter a number with the keyboard or the on-screen number pad. Choose a difficulty from Beginner to Grandmaster; each level has a set number of clues and hints, and the Note Assistant tracks candidates for you.
Background
The modern puzzle was published in the United States in 1979 as Number Place. It became popular in Japan in the 1980s, where the publisher Nikoli gave it the name Sudoku, and it spread worldwide after British newspapers began printing it in 2004.
Frequently Asked Questions
Do I need to be good at math to play Sudoku?
No. Sudoku uses digits only as symbols. It is a logic puzzle, not an arithmetic one.
How many difficulty levels are there?
Levels range from Beginner to Master and Grandmaster, with fewer clues and hints as the difficulty rises.
What should I do when I get stuck?
Fill in candidate notes and look for pairs of cells that share the same two options. Our Sudoku solving techniques guide covers these methods.