Sudoku Rules
Classic Sudoku uses a 9×9 grid. Fill every row, column, and 3×3 box with the digits 1 through 9 — no repeats in any row, column, or box.
Each row
Every horizontal row must contain the digits 1–9 exactly once.
Each column
Every vertical column must contain the digits 1–9 exactly once.
Each 3×3 box
Every 3×3 box must contain the digits 1–9 exactly once.
Guides & articles
How to Play SudokuA complete beginner guide to classic 9×9 Sudoku — rules, first steps, pencil marks, and how to finish your first puzzle.Sudoku Tips for BeginnersPractical habits that speed up beginners — scanning patterns, pencil marks, difficulty progression, and common mistakes to avoid.Naked Single Sudoku StrategyLearn the naked single technique — when a cell has only one possible candidate left and how to spot it quickly.