Sudoku is a logic-based number puzzle played on a 9x9 grid. The goal is to fill every row, column, and 3x3 box with the digits 1-9, each appearing exactly once.

Do you need to be good at maths to solve Sudoku?

No. Sudoku requires no arithmetic. It is purely a logic puzzle based on elimination and deduction.

What is the best strategy for beginners?

Start with scanning (cross-hatching) to find cells where only one number can go. Then learn Snyder Notation to track pencil marks efficiently.

What is the difference between Easy and Hard Sudoku?

Easy puzzles have more given numbers (around 36) and can be solved using basic scanning. Hard puzzles have fewer givens (around 25) and require advanced techniques like X-Wings or Swordfish.

Sudoku FAQ: Common Questions Answered

About Sudoku Index

What is Sudoku Index?

Sudoku Index is a comprehensive directory of the best Sudoku websites, mobile apps, books, and learning resources. We curate and review hundreds of Sudoku platforms to help enthusiasts of all skill levels find their perfect puzzle experience. Our mission is to be your one-stop destination for all things Sudoku.

How are sites reviewed and rated?

Our team thoroughly tests each site, app, and book before adding it to our directory. We evaluate based on:

User experience and interface quality
Puzzle variety and difficulty levels
Features and functionality
Community feedback and ratings
Value for money (for paid resources)

Users can also rate and review sites based on their experiences!

Is Sudoku Index free?

Yes! Sudoku Index is completely free to use. We help you discover Sudoku resources, many of which are free, though some premium options are also included. You can browse our entire directory, read reviews, and access our knowledge base at no cost.

How do I submit a site to Sudoku Index?

You can submit your Sudoku site, app, or resource using our "Add Listing" form on the homepage. Simply fill in the details about your platform, and our team will review it for inclusion in our directory. We aim to feature quality resources that add value to the Sudoku community.

Getting Started with Sudoku

I'm a complete beginner. Where should I start?

We recommend starting with our How to Play Sudoku guide to learn the basic rules. Then, check out our directory's "Play" category for beginner-friendly websites. Start with Easy difficulty puzzles to build confidence!

What are the basic rules of Sudoku?

Sudoku is played on a 9x9 grid divided into 9 3x3 boxes. The goal is to fill in the grid with numbers 1-9 such that:

Each row contains all numbers 1-9
Each column contains all numbers 1-9
Each 3x3 box contains all numbers 1-9

For a detailed explanation, visit our How to Play guide.

What's the difference between Easy, Medium, Hard, and Expert puzzles?

Difficulty levels refer to how many clues are given and how complex the solving logic required is:

Easy: 50+ clues, solvable with basic techniques
Medium: 40-50 clues, requires some intermediate strategies
Hard: 30-40 clues, requires advanced solving techniques
Expert: Less than 30 clues, requires mastery of all techniques

Solving Strategies

What are the most useful Sudoku solving techniques?

Key techniques include:

Naked Singles: A cell where only one number can fit
Hidden Singles: A number that can only fit in one cell in a row/column/box
Naked Pairs/Triples: Multiple cells with the same candidates
Pointing Pairs: Candidates that eliminate possibilities elsewhere
X-Wing & Swordfish: Advanced pattern recognition

Learn more in our Advanced Techniques guide.

Should I use a pencil marking system?

Yes! For harder puzzles, using pencil marks (writing candidate numbers in cells) is essential. This helps you track possibilities and spot patterns. Many online platforms automatically manage pencil marks for you.

What should I do if I get stuck?

If you're stuck:

Take a break and come back with fresh eyes
Review your pencil marks carefully
Try a different solving technique
Use the hint feature if available on the platform
Consider a Sudoku solver to check your work
Read our Tips and Tricks for more strategies

Finding Resources

What's the best free Sudoku website?

There's no single "best" site - it depends on your preferences! Check our Directory and filter by category or read user reviews to find the perfect site for you. Popular free options include WebSudoku, SudokuOnline, and Puzzle Picnic.

Are there good Sudoku apps?

Yes! Check our Apps section for top-rated Sudoku applications for mobile devices. We review apps across iOS and Android with features like offline play, hints, and leaderboards.

Should I buy a Sudoku book?

Physical Sudoku books are great for:

Screen-free puzzle solving
Travel and commuting
Practicing pencil-and-paper solving
Variety with curated puzzle collections

Browse our Top Books section for highly-rated options.

Contact & Support

How do I contact Sudoku Index?

You can reach us using our Contact Form. We read all inquiries and will get back to you as soon as possible with answers to your questions.

How do I subscribe to the newsletter?

You can subscribe to our newsletter on the homepage using the newsletter signup form. You'll receive updates about new site reviews, solving tips, and exclusive content.

How often is content updated?

We regularly add new site reviews, update existing content, and publish new blog posts. Subscribe to our newsletter to stay updated on the latest additions and improvements to Sudoku Index!