How to Play Sudoku
Classic Sudoku puzzles. Fill every row, column, and 3×3 box with digits 1–9. Free online, no download needed.
Try it now — Easy 9x9 →The Rules
- Fill every row with digits 1–9 exactly once
- Fill every column with digits 1–9 exactly once
- Fill every 3×3 box with digits 1–9 exactly once
- Pre-filled clue cells are fixed — never change them
Available in 3 sizes (4x4, 6x6, 9x9) and 4 difficulty levels (easy, normal, hard, expert).
See It in Action
Click an empty cell and enter a digit — each number once per row, column, and box
How to Play
- Scan rows, columns, and boxes for nearly-complete lines — the missing digit goes in the only empty cell
- Use "naked singles": a cell where only one digit is possible given its row, column, and box
- Use "hidden singles": a digit that can only fit one cell within a given row, column, or box
- Repeat until every cell is filled — every valid Sudoku has exactly one solution
Pro Tips
Start where you see the most given digits — those rows, columns, and boxes have the fewest possibilities
Write small candidate numbers in a cell's corner to track what's still possible
If a digit appears in two rows of a band, eliminate it from the third row within the same band's boxes
Frequently Asked Questions
What are the rules of Sudoku?
Fill a 9×9 grid so that every row, every column, and every 3×3 box contains each digit from 1 to 9 exactly once.
What is the easiest way to start a Sudoku?
Look for rows, columns, or boxes that already have the most numbers filled in — these have the fewest possibilities. The "naked single" technique (a cell with only one possible digit) is the most reliable starting point.
Choose Your Challenge
Start with easy to learn the rules, then progress to harder difficulties.