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
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
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
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.
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.
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.