How to Play Sudoku

What is Sudoku?

Sudoku is a logic-based number puzzle played on a 9×9 grid. The grid is divided into nine 3×3 boxes. Your goal is to fill every empty cell with a number from 1 to 9 — following three simple rules.

The Three Rules

Step-by-Step: Solving Your First Puzzle

1. Scan for easy cells. Find rows, columns, or boxes that already have 7 or 8 numbers. The missing digit is the only option.
2. Use elimination. For each empty cell, eliminate numbers already present in the same row, column, and box. If only one number is left, place it.
3. Look for hidden singles. In a group (row, column, or box), find a number that can only fit in one cell. Place it there.
4. Use pencil marks (notes). In harder puzzles, write small candidate numbers in empty cells. Cross them off as you make placements.
5. Repeat. Each number you place reveals more information. Keep scanning until the board is complete.

Basic Strategies

Cross-Hatching

Pick a digit (say, 5). Draw imaginary lines through every row and column that already contains a 5. The cells where no lines cross — inside each 3×3 box — are your candidates. Often only one cell remains.

Naked Singles

An empty cell where elimination leaves only one possible candidate. This is the simplest and most common move in easy and medium puzzles.

Naked Pairs

Two cells in the same group that both contain only the same two candidates. These two numbers are "locked" in those two cells — you can safely remove them from all other cells in the group.

Tips for Beginners

• Start with the Easy difficulty to learn the basics.
• Never guess — every Sudoku puzzle has a unique logical solution.
• Use the notes feature in SUDOQIO to pencil in candidates (press N or tap the pencil icon).
• The app auto-clears notes when you place a correct digit — keeping your board clean.
• Practice the daily puzzle every day to build speed and pattern recognition.