What Is Sudoku? Rules, Variants & a Beginner’s Quickstart

1 Definition & Goal

Sudoku is a logic puzzle on a 9×9 grid with a single correct solution. Fill every row, column, and 3×3 box with digits 1–9 without repetition. Success comes from deduction and candidate elimination—not guessing.

2 Core rules in a nutshell

• Rows/Columns: Each digit 1–9 appears exactly once.
• Boxes: Each 3×3 box also contains 1–9 once.
• Given clues: Starting digits are fixed and anchor the logic.

These rules ensure logical fairness and an elegant solving experience.

3 Why people love it

Short sessions, constant progress, and a rewarding “aha” loop. Regular solving boosts focus, working memory, and pattern recognition.

4 Popular variants

• Classic 9×9: The standard and best starting point.
• Mini (4×4, 6×6): Quick practice and great for kids.
• Advanced: Killer, Thermo, Diagonal, Irregular—extra constraints for deeper logic.

Variants extend the logic layers without changing the spirit of Sudoku.

5 First steps without guessing

• Scan: Start with units that are almost complete.
• Candidates: Pencil-mark possibilities and update after every placement.
• Singles: If a cell has only one option, place it.
• Eliminate: Remove impossible candidates to trigger new deductions.

With practice, techniques like Naked/Hidden Singles, Naked Pairs, and X-Wing become intuitive.

6 Tips & common pitfalls

• Don’t guess—change perspective and re-scan.
• Keep notes tidy and up to date.
• If stuck, switch regions and look for fresh constraints.

Try daily puzzles on Ozerlyn Sudoku to improve both speed and accuracy.

7 Conclusion

What is Sudoku? A clean, fair test of logic where patience and structure win. Master the basics and you’ll unlock even the hardest grids—one deduction at a time.