How to Play

Learn sudoku step by step and become an expert

Table of Contents

  1. What is Sudoku?
  2. Sudoku Types
  3. Basic Rules
  4. How to Play
  5. Solving Techniques
  6. Tips and Strategies
  7. Keyboard Shortcuts

1. What is Sudoku?

Sudoku is a logic-based number puzzle from Japan. The goal is to fill the empty cells so that each row, each column, and each block contains all numbers from 1 to N exactly once.

💡 History

Sudoku was first published in 1979 in America under the name "Number Place". It became popular worldwide in 2004 when it spread from Japan to the UK.

Benefits of Sudoku

  • 🧠 Brain Exercise: Strengthens memory and concentration
  • 🎯 Logic Skill: Improves problem-solving ability
  • 🧘 Stress Relief: Calms the mind and helps focus
  • ⏰ Time Management: An efficient way to spend time

2. Sudoku Types

4x4 Sudoku (Mini)

1
2
3
4
2
1
4
3

Size: 4x4 (16 cells)

Block: 2x2

Numbers: 1-4

Level: Beginner

Ideal for children and beginners. Best choice to learn the basic logic.

6x6 Sudoku (Medium)

1
4
2
5
3
6
4
1
5
2
6
3

Size: 6x6 (36 cells)

Block: 2x3

Numbers: 1-6

Level: Medium

Perfect transition between 4x4 and 9x9. Suitable for those looking for light challenge.

Most Popular

9x9 Sudoku (Classic)

5
3
7
6
1
9
5
9
8
6
8
6
3
4
8
3
1
7
2
6
6
2
8
4
1
9
5
8
7
9

Size: 9x9 (81 cells)

Block: 3x3

Numbers: 1-9

Level: home.difficulty.standard

Classic sudoku experience. The most played version worldwide.

Difficulty Levels

Easy

38-45 clues given. Ideal for beginners.

Medium

30-37 clues given. Basic techniques are sufficient.

Hard

25-29 clues given. Requires advanced techniques.

Expert

17-24 clues given. The hardest level, requires mastery.

3. Basic Rules

📏

Row Rule

Each horizontal row must contain each number used exactly once.

3
1
4
2

Correct: Each number once

3
1
4
3

✗ Incorrect

📐

Column Rule

Each vertical column must contain each number used exactly once.

2
1
4
3

Correct: Each number once

2
1
4
1

✗ Incorrect

🔲

Block Rule

Each block (sub-grid) must contain each number used exactly once.

1
4
3
2

Correct: Each number once

1
4
3
1

✗ Incorrect

⚠️ Important Reminder

All three rules must be satisfied simultaneously. When entering a number, check the row, column, and block.

4. How to Play

1

Start Game

Play Go to the Play page. Select sudoku type (4x4, 6x6, 9x9) and difficulty level. Click "New Game" button.

🎮 The game board will open with some cells pre-filled.

2

Select Cell

Click on an empty cell to select it, or use arrow keys to navigate. Selected cell is highlighted in blue.

💡 Tip: Related cells in the same row, column, and block are also highlighted.
3

Enter Number

You can enter numbers in two ways:

  • On-screen keypad: Click the number buttons
  • Keyboard: Press number keys 1-9
4

Delete and Correct

If you entered a wrong number:

  • Select the cell and enter a new number
  • Delete with Backspace or Delete key
  • Click the delete button on screen
5

Use Hint

When stuck, click the Hint button. The system will show you the correct number for a cell.

⚠️ Each hint reduces your score. Use as few hints as possible!

6

Complete Game

When all cells are correctly filled, the game ends! Your time, mistakes, and hint usage are recorded. Take your place on the leaderboard!

🏆 The faster and with fewer errors you complete, the higher your score!

5. Solving Techniques

🔤 Technique 1: Elimination Method (Simplest)

Find which numbers cannot go in a cell - the remaining single option must be correct.

5
?
3
6
?
4
1
2
?

Example:

  • Row contains: 5, 3
  • Column contains: 6, 1
  • Block contains: 5, 3, 6, 4, 1, 2

Result: 4 Only

🔢 Technique 2: Find Missing Number

If only one cell is empty in a row, column, or block, find which number is missing.

1
3
4
?

Example: This row has 1, 3, 4. Missing: 2

🎯 Technique 3: Single Possibility

For a number, there may be only one valid position within a row/column/block.

?
2
?
1
?
3
?
?
?

Example: The middle column cannot have 1 (row 2 already has 1). Similarly 3 cannot go. Only 2 is possible but row 2 already has it.

Analyze other numbers this way.

📝 Technique 4: Note Taking (Marking)

In difficult sudokus, write possible numbers in each cell in small text. Then eliminate to narrow down.

1 3 7

This cell can only be 1, 3, or 7. Narrow this list with more information.

💡 Advanced Techniques

For harder sudokus, these techniques are also used:

  • X-Wing: When a number has only two possible positions in two rows
  • Swordfish: 3-row version of X-Wing
  • Hidden Pairs: Two numbers can only go in two cells together
  • Naked Triples: Three cells have the same three candidate numbers

These techniques can be learned as you master. Basic techniques are enough for beginners!

6. Tips and Strategies

🎯

Start Easy

If you are new, start with 4x4 sudoku. Once you understand the logic, increase the size.

🔍

Look for Most Clues

Find the row, column, or block with the most filled cells. More clues = easier solution.

✏️

Take Notes

In difficult games, write possible numbers in small. This helps you eliminate later.

⏸️

Take a Break

When stuck, take a short break. When you return, you will see with fresh eyes.

🚫

Don't Guess

Sudoku is a logic game, not chance. Verify each move with logic.

⏱️

Track Time

Solving quickly increases your score, but accuracy is more important. Don't rush.

🔄

Regular Scanning

Scan all rows, then all columns, then all blocks. Progress systematically.

🏆

Play Every Day

Regular practice improves your skills. Solve at least one sudoku every day.

7. Keyboard Shortcuts

Key Function
1 - 9 Enter number in selected cell
← → ↑ ↓ Navigate between cells
Backspace / Delete Delete selected cell
H Get hint
N Start new game
Tab Go to next empty cell

Start Playing Now!

Start a game right now to put what you learned into practice.

🎮 Start Playing 📥 Download