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Play Chess against the computer or your friends!
Challenge the computer or try online matchmaking!
Outsmart your opponent in the game of X's and O's.
Skip All Ads: Go Premium NowSudoku Instructions
To play our free online Sudoku game, tap and hold a number to lock it and you can use it for multiple cells. Use the numbers 1-9 in each of the 9 rows, 9 columns, and 3x3 boxes of the Sudoku grid. Use the orange guide to see which numbers you've already used in each row, column, and box. You can change the difficulty level in Sudoku from beginner to intermediate or advanced if you want to solve more difficult puzzles. Try timing yourself to see how fast you can beat a given puzzle.
Tips for Playing Sudoku
Try using the following techniques to solve Sudoku puzzles.
Focus on a specific part of the puzzle
When solving Sudoku puzzles, players often feel as if they need to solve the entire puzzle from the beginning. But that’s not the case. Any one Sudoku puzzle contains multiple puzzles within it. Start by focusing on a column, row or box. Once you’ve solved that piece of the puzzle, move on to the next part.
Spot the missing numbers
Beneath each puzzle are buttons you use to enter the numbers 1 to 9. Each of these buttons has a small number in the top right corner -- that’s the number of times that the big number already appears on the board. Start with the big numbers that appear most often. For example, if the 7 button has a small 5 in the top right corner, that means there are already five 7s on the board. You can click a 7 on the board to highlight all five 7s in the puzzle. Use this to figure out which rows, columns, and boxes don’t yet have a 7. That makes it easier to place the remaining 7s.
Fill in the Candidates
A “candidate” is a number that could fit in a spot, even though other numbers might fit there too. When solving a puzzle, try filling in empty spots with all the candidates that might fit there. You can do this by clicking the button with the large black dot, and then adding candidates to the spot. The candidates will appear as little numbers. Many beginners don’t bother to use candidates, but that’s a mistake. Candidates are essential when solving difficult puzzles.
Look for Hidden Singles
This one’s pretty simple. Once you’ve filled in all the candidates, look for a candidate that appears only once in a particular row, column, or box. If you find one, that candidate must be in the correct spot, regardless of other candidates in that same spot. Find the Naked Pairs When a box has two spots in which you can enter only the same two candidate numbers (let’s say 6 and 8), that’s a good clue! When that happens, take a look at the other spots in that box. You can eliminate the 6 and 8 from the other spots. You’re still not sure which spot contains the 6 and which contains the 8, but you’ve narrowed it down a lot.
What Do Sudoku Games Teach You?
Sudoku puzzles stimulate your mind and help you practice logical reasoning. While playing this game, you increase your concentration, develop your memory and promote strategic thinking.
To play our free online Sudoku game, use your mouse and keyboard to fill in the blanks by clicking and placing numbers in the grid. Use the numbers 1-9 in each of the 9 rows, 9 columns, and 3x3 boxes of the Sudoku grid. Use the orange guide to see which numbers you've already used in each row, column, and box. You can change the difficulty level in Sudoku from beginner to intermediate or advanced if you want to solve more difficult puzzles. Try timing yourself to see how fast you can beat a given puzzle.
Online Sudoku Tips
Try using the following techniques to solve Sudoku puzzles.
Focus on a specific part of the puzzle
When solving Sudoku puzzles, players often feel as if they need to solve the entire puzzle from the beginning. But that’s not the case. Any one Sudoku puzzle contains multiple puzzles within it. Start by focusing on a column, row or box. Once you’ve solved that piece of the puzzle, move on to the next part.
Spot the missing numbers
Beneath each puzzle are buttons you use to enter the numbers 1 to 9. Each of these buttons has a small number in the top right corner -- that’s the number of times that the big number already appears on the board. Start with the big numbers that appear most often. For example, if the 7 button has a small 5 in the top right corner, that means there are already five 7s on the board. You can click a 7 on the board to highlight all five 7s in the puzzle. Use this to figure out which rows, columns, and boxes don’t yet have a 7. That makes it easier to place the remaining 7s.
Fill in the Candidates
A “candidate” is a number that could fit in a spot, even though other numbers might fit there too. When solving a puzzle, try filling in empty spots with all the candidates that might fit there. You can do this by clicking the button with the large black dot, and then adding candidates to the spot. The candidates will appear as little numbers. Many beginners don’t bother to use candidates, but that’s a mistake. Candidates are essential when solving difficult puzzles.
Look for Hidden Singles
This one’s pretty simple. Once you’ve filled in all the candidates, look for a candidate that appears only once in a particular row, column, or box. If you find one, that candidate must be in the correct spot, regardless of other candidates in that same spot. Find the Naked Pairs When a box has two spots in which you can enter only the same two candidate numbers (let’s say 6 and 8), that’s a good clue! When that happens, take a look at the other spots in that box. You can eliminate the 6 and 8 from the other spots. You’re still not sure which spot contains the 6 and which contains the 8, but you’ve narrowed it down a lot.
What Do Sudoku Puzzle Games Teach You?
Sudoku puzzles stimulate your mind and help you practice logical reasoning. While playing this game, you increase your concentration, develop your memory and promote strategic thinking.
Can Sudoku Increase your IQ?
While there is still debate over how effective Sudoku is at increasing your IQ, it is generally agreed among scientists that games such as Sudoku increase several cognitive functions. According to psychologist Peter Gray, playing games can help increase problem-solving abilities and reasonable decision-making.
To learn more about this, you can read our Coolmath Games blog which aims to answer the long-debated question – are video games good for you?
What are the 3 main rules for Sudoku?
There are 3 main rules that you must follow in order to play Sudoku. While all of them are fairly similar, you must follow each rule to the tee in order to solve the puzzle.
- Every single column (vertical) must have every single number, from 1 to 9, with no repetitions.
- Every single row (horizontal) must have every single number, from 1 to 9, with no repetitions.
- All 9 large boxes in the puzzle must have every single number, from 1 to 9, with no repetitions.
While there are certainly other small rules to Sudoku, such as no guessing, these are the 3 main rules that you absolutely must follow. To learn more about the rules of Sudoku, go check out our Coolmath Games blog on how to play Sudoku.
What is the trick to playing Sudoku?
As we previously mentioned, the main ‘trick’ to Sudoku is to scan through the board and search for rows and columns that already have a lot of numbers in them. You can eliminate these numbers from the other unfilled boxes. This should hopefully help you out a lot.
However, harder puzzles may require more than just this. To learn some more in-depth Sudoku strategies, you can check out our blog all about Sudoku Strategy if you are ever feeling puzzled.
How old is Sudoku?
Most historians agree that Sudoku was created by Howard Garnes, a puzzle constructor from Indiana. It was created in 1979, originally published under the name Number Place.
However, the history goes much deeper than this. It took quite a while for online Sudoku to show up. To learn about all of the fascinating details of online Sudoku, check out our blog all about the history of Sudoku.
What are Games Like Sudoku?
- Chess: Play Chess against the computer or your friends!
- Checkers: Challenge the computer or try online matchmaking!
- Tic Tac Toe: Outsmart your opponent in the game of X's and O's.
- Strategic Tic-Tac-Toe: Are you a Tic Tac Toe pro? Try this version!
- Reversi: Cover the board with your color in this classic game.
- Back- gammon: Get all your pieces off the board.
- Peg Solitaire: Make the right jumps to get down to one.
- Dominoes: Be the first to play all your tiles!
- Dots and Boxes: The digital version of the pencil-and-paper classic.
How to play Sudoku on your phone
Did you know you can also play Sudoku on your phone? It’s a great way to play without worrying about losing your save data.
For iOS devices, simply tap the "Share" icon 
in Safari and select "Add to Home Screen". For Android devices, tap the “Menu” icon 
and select "Install App".
