How to Play Sudoku
The Goal
Fill the 9×9 grid with numbers 1-9 so that each row, column, and 3×3 box contains all digits from 1 to 9 without repetition.
Rules
- Each row must contain the numbers 1-9 exactly once
- Each column must contain the numbers 1-9 exactly once
- Each 3×3 box must contain the numbers 1-9 exactly once
- Some numbers are already filled in - these cannot be changed
Getting Started
- Look for rows, columns, or boxes that already have many numbers filled in
- Check what numbers are missing from that section
- Use logic to determine where the missing numbers must go
- Start with easier cells that have only one possible answer
Using Our Tools
Pencil Marks
Enable "Pencil" mode to write small candidate numbers in cells. This helps you keep track of possibilities as you work through the puzzle.
Hints
If you're stuck, click the "Hint" button to get a suggestion for your next move. The hint system uses human-solving strategies to guide you.
Undo/Redo
Made a mistake? Use the Undo button to go back. You can also Redo moves if needed.
Difficulty Presets
Pick the preset that matches your mood. Each option maps to a board size and ruleset.
- I'm New
- Mini board with beginner logic and no diagonals. (6×6 classic — engine difficulty: beginner)
- Finding My Way
- Standard board with gentle clues. (9×9 classic — engine difficulty: easy)
- Weekend Warrior
- Balanced difficulty for regular players. (9×9 classic — engine difficulty: medium)
- Try Me
- 9×9 puzzle with diagonal constraints. (9×9 with diagonal constraints — engine difficulty: medium)
- Professional
- Hard logic plus diagonal rules. (9×9 with diagonal constraints — engine difficulty: hard)
- Expert
- Maximum difficulty with diagonal play. (9×9 with diagonal constraints — engine difficulty: expert)
- God-Like
- Massive 12×12 grid with diagonal rules. (12×12 with diagonal constraints — engine difficulty: expert)
Diagonal puzzles require each main diagonal to also contain all numbers exactly once. The God-Like preset uses a 12×12 grid, so you'll be entering digits 1–12.
Tips for Success
- Start with the easiest cells first
- Use pencil marks to track possibilities
- Look for "naked singles" - cells with only one possible number
- Check each row, column, and box systematically
- Take breaks if you get frustrated - fresh eyes help!
- Practice regularly to improve your skills
Accessibility Features
Our Sudoku game is designed to be accessible for everyone:
- Adjustable text size (125%, 150%, 175%)
- High contrast mode for better visibility
- Dark mode option
- Full keyboard support for navigation
- Screen reader compatible
- Large touch targets for easy clicking