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Sudoku Online

Sudoku Mood - explore the world of countless high-quality Sudoku puzzles online. It's free. It's simple to use. It's fun.

What is Sudoku

What is Sudoku

Sudoku is a numbers puzzle. It does not require any math, though. In fact, if we replace numbers with letters, shapes, or even colors - the puzzle won't change.

Sudoku rules

Sudoku rules

You are given a square 9x9 grid. Some cells are empty, some contain digits. Fill all empty cells with digits 1 to 9 so that each digit appears exactly once in each row, each column, and each 3x3 block.

Play your first Sudoku game

Play your first Sudoku game

If you wonder how to start, just choose Easy Sudoku and give it a try. You'll quickly get the idea. Enjoy your first web Sudoku!

Why Sudoku Mood

There are many web Sudoku sites that allow you to play Sudoku online for free. But once you try Sudoku Mood, you’ll love it the most.

High-quality puzzles
We've carefully crafted all our Sudoku puzzles to ensure that each of them is interesting to solve, no matter what level of difficulty you prefer.
We respect our users
We show you the bare minimum of ads and refrain from all kinds of obtrusive ads. No annoying video ads every time you start a game or need to use a hint.
User friendly
Sudoku Mood was designed with simplicity in mind. Our goal is to make sure that users will be able to fully enjoy our website right after they see it for the first time.
Intelligent hints
Our smart hint function is always able to provide you with a full explanation of how the next move can be logically achieved without any guessing.
Modern look
Sudoku Mood is a modern website with a clean and minimalistic design. You can enjoy it on all platforms, including iPhone, iPad and Android.
Cool features
We offer you a unique and well-balanced set of functions that improve your Sudoku solving experience and make it more fun.

Choose the right Sudoku difficulty

Choosing the right difficulty is the key to having fun. Here's how to do that:

Choose it if you never played Sudoku before or if you're short on time. It's perfect for a coffee break.
A step up in challenge, requires a bit more thinking. It's the most popular choice among our players.
Best for experienced Sudoku players. Be ready to scratch your head a couple of times to find a solution.
Choose it if you are looking for a really challenging Sudoku. Finding a solution without the use of pencil notes is almost impossible.
Reserved for Sudoku enthusiasts familiar with advanced solving techniques.

How to play Sudoku

Start with the obvious

Look for a 3x3 block, row, or column with only one empty cell left. Fill in the missing digit.

Start with the digit 1 and look for 3x3 blocks where there is only one cell in which this digit can be placed. Repeat the process for other digits.

Do the same with rows and columns - try looking for rows and columns where there is only one cell in which a particular digit can be placed.

Learn or practice

There are many different approaches to look for the next cell to solve. These approaches are usually called techniques. Over time, Sudoku fans gave names to each technique. For instance, the techniques described in the section above are called Last Digit and Hidden Single.

You can learn Sudoku solving techniques by reading how to use them. Or you can just practice solving Sudoku puzzles, and over time you’ll start using many techniques intuitively without even knowing their names. After all, Sudoku solving technique is nothing more than a formal definition of logical steps that allow you to make the next move.

Do what you like more - read about Sudoku solving techniques or just play Sudoku online and learn by practicing.

Keep it simple

Some Sudoku solving techniques are more difficult and time-consuming than others. Use the simplest techniques first. Proceed to more difficult techniques only if all simpler techniques haven’t helped you to find a cell to fill.

Return to the simplest techniques every time you find a cell to fill - a new filled cell might have made it possible to apply simple techniques again even if you used more difficult techniques to solve that cell.

Apply each Sudoku solving technique meticulously. If you overlook the possibility of filling a cell with a simple technique, you might spend a lot of time and unnecessary effort on the difficult techniques.

Be patient

Don’t be sporadic. Trying to spot the next cell to fill without carefully scanning the whole grid rarely works out.

Take your time and be patient. The more difficult Sudoku puzzle you choose to play, the more patience you’re gonna need.

If it doesn’t feel fun anymore, take a break and return to it later. Or the next day - your Sudoku game gets saved automatically.

Use pencil notes. Or not

Some Sudoku players prefer to use pencil notes, some don't. There is no right or wrong here. It's just two distinct approaches that make the solving experience totally different.

Solving without pencil notes makes the puzzle more difficult. However, this could be exactly what you want. Especially if you are solving Easy or Medium Sudoku. Or even Hard Sudoku.

When you solve with pencil notes you maintain a list of feasible candidates in each cell and eliminate those candidates one by one. Candidate digits that can't be placed in a cell because there's already such a digit in a row, column or block, are eliminated automatically.

You can use the "Fill Candidates" and "Clear Candidates" buttons in the "More" section. Or you may even turn on the function "Fill candidates automatically when a new game starts" - it will fill candidates in each cell every time a new Sudoku game is started. Again, it's a matter of preference - some players like to fill in candidates themselves, some - don't.

If you get stuck

There are a few things you can do:

  • Check out whether you know all the techniques required for this Sudoku level. You can find the list of techniques on each level page.
  • Take a break. Maybe you’re too tired.
  • Try to look for simple moves. You might have overlooked some simple to fill cells and then wasted time on more difficult logic.
  • Use the hint function. It will show and explain you the easiest move available, and next time you won’t miss it.

Get to know Sudoku Mood

Use the right techniques

Each level at Sudoku Mood requires a different set of techniques in your toolbox. For your convenience, all required techniques are listed on each level page. For instance, on the Hard Sudoku page you’ll find a list of techniques required to solve Hard Sudoku.

Understand the time-to-solve indicator

You’ll notice a horizontal bar with five sections next to the grid. It indicates how much time it takes to solve the current Sudoku puzzle compared to other Sudoku puzzles of the same level. You can use it to further tune the desired Sudoku difficulty.

Don't guess. Use hints

There's always a way to fill some cell on the grid without any guessing. If you can't find the next cell to fill, use a hint instead of guessing. Hints will teach you how to play better.

Delete mistakes

If you made a mistake, delete it using the "Erase" button or "Undo" button.

Use keyboard

You can use a keyboard to put a digit into a cell or to delete a digit from a cell.

Use highlight function

When you click on a grid cell with a digit, its row, column, and block get highlighted. All other cells containing this digit will be highlighted too. Highlight function dramatically reduces the complexity of many Sudoku solving techniques as it gets much easier to spot what you are looking for.

Save your Sudoku game and play it later

Your game gets saved automatically. You can take a break and continue playing where you left off. The saved game will load the next time you visit Sudoku Mood, even if you closed your browser or even if it's been a while since you played your Sudoku game.

Fun facts about Sudoku

Sudoku is not a Japanese puzzle, only its name is

The first Sudoku puzzle was published by Howard Garns in 1979 in an American puzzle magazine. Originally it was called the Number Place. The puzzle hasn’t become very popular though. In 1984 it was brought to Japan, where it gained its popularity and name - Sudoku. The term Sudoku, or Su-Doku, is derived from Japanese words meaning "the digits must be single". In 2004 Sudoku puzzle was published in the British newspaper The Times and since then it has become popular worldwide.

Sudoku phenomena

The first publication of Sudoku in a British newspaper caused a kind of chain reaction. First, many other newspapers in Britain started publishing Sudoku puzzles. Before long it spread abroad, and newspapers around the world added Sudoku to their entertainment sections or supplements.

People loved Sudoku puzzles so much that the entertainment industry couldn’t ignore it. TV shows and documentaries about Sudoku appeared and viewers loved them too. Sudoku fans even composed a song about Sudoku, which appeared on radio in several countries.

As some fans kept mastering their skills, Sudoku competitions appeared around the world. In 2006 the first World Sudoku Championship was held.

Benefits of playing Sudoku

Playing Sudoku online is fun, so it’s a perfect way to relax. It helps you to clear your thoughts and gives you a sense of achievement when you finish the Sudoku puzzle.

Sudoku develops logic. Kids playing Sudoku can improve their problem solving skills and logical thinking. And because it’s not boring they will love doing it.

According to scientific research, playing Sudoku game reduces the risk of Alzheimer’s. It stimulates the human brain and helps it function better as you age.