Sudoku Instructions

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.




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.




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.

Sudoku Instructions

Use the numbers 1-9 in each row, column, and 3x3 square of the board. See how fast you can solve the puzzle. If it's too hard or easy, you can start a new puzzle with a different difficulty.

20,305 Votes

Sudoku Instructions

Use the numbers 1-9 in each row, column, and 3x3 square of the board. See how fast you can solve the puzzle. If it's too hard or easy, you can start a new puzzle with a different difficulty.

Coolmath Top Picks

Checkmate! Play the classic game of strategy. You can challenge the computer, a friend, or join a match against another online player.

Play Chess against the computer or your friends!

Swing through the jungle from tree to tree! Beat levels to unlock new monkey skins.

Monkey swing, monkey do!

Hop in your helicopter and join this strategic multiplayer game. Specialize your copter, build a base, and conquer the map!

Cash in your coins for all new skins!

Hop in your hot air balloon and prepare for adventure! Solve a whole new quest on every island.

Hop in your hot air balloon and prepare for adventure!

Test your aim in online multiplayer! Race your opponent to get to zero first. You'll have to calculate your own score.

Test your aim in online multiplayer!

Play the classic game, or mix it up with an all-new action mode: fireballs, blasters, gravity wells, and more!

Play the classic game or the all-new action mode!

Your pineapple is trapped at the top of a huge tower! Jump over pits of lava and dodge dangerous traps to rescue it.

Save your pineapple from evil Big Square!

Grow your civilization during the Bronze Age. Collect food, research technology, defend yourself from other civilizations, and build a world wonder!

Grow your civilization.

In this strange and unusual world, you cannot jump. Fortunately, you CAN summon mountains beneath your feet. And get filthy stinkin' rich.

You can't jump. But you can move mountains.

Let's get rolling! It may not look like much at first, but we have a feeling you'll be earning trillions of points in no time.

Let's get rolling!

Hit a screamer into the top corner or make an epic save in this penalty shootout. Take your skills online and become world champion!

Test your soccer skills in online multiplayer!

Fill the board with bricks! How many points can you score before you get stuck?

Fill the rows and columns with colorful bricks!

Step up and spin the wheel in this cool way to learn about probability! Guess higher or lower to win big points. Will you play it safe or risk it all?

Step up and spin the wheel!

Looks like a nice day to go fishing! Cast your line and reel in a legendary fish. Earn cash to buy new hooks and skills.

Cast your line and reel in a legendary fish!

The pig is on the loose! Help prevent him from escaping by placing stone walls to block his path.

The Pig is on the loose! Can you catch him?

Connect all pipes of the same color. The pipes can't cross, and you have to fill all of the space with pipes!

Connect pipes of the same color.