Sudoku Online - Classic Logic Puzzle Game

Play Sudoku Online for Free

Sudoku is one of the most popular logic puzzles in the world, and Foony's version takes it further with multiplayer, co-op, collectible boards, and four difficulty levels. Fill the 9x9 grid so that every row, column, and 3x3 box contains the digits 1 through 9. No math required, just logic and focus.

• Four Difficulty Levels: Easy, Medium, Hard, and Expert puzzles to match your skill level.
• Three Game Modes: Casual (unlimited mistakes), Normal (3 mistakes allowed), or Perfectionist (one mistake and you're done).
• Multiplayer and Co-op: Solve puzzles alongside friends or compete against up to 1,000 players at once.
• Collectible Boards and Pieces: Earn and equip custom board styles and number sets as you level up.
• Achievements and Rewards: Unlock achievements like Flawless Victory, Puzzle Master, and Zen Master to earn rare items.

How to Play Sudoku

Every Sudoku puzzle starts with a 9x9 grid partially filled with numbers. Your goal is to fill in the remaining empty cells so that every row, column, and 3x3 box contains the numbers 1 through 9 exactly once.

Click or tap an empty cell, then select the number you want to place. If you're not sure about a number, use the pencil tool to mark candidates in a cell. Later on we'll add support for Hints if you get really stuck. For now, if you're playing with unlimited mistakes, it might make sense to strategically guess to help you figure out other cells on harder difficulties (but it's not required).

Difficulty Levels

Foony's Sudoku offers four difficulty settings that control how many cells are pre-filled and how complex the logic required to solve the puzzle is.

• Easy: Great for beginners. Cells can be solved with basic elimination. This is my personal favorite because it's easy, but you'll get less exp and gold compared to higher difficulties.
• Medium: Requires a bit more thought. You'll need to scan rows, columns, and boxes carefully.
• Hard: Expect to use pencil marks. Multiple elimination techniques come into play.
• Expert: The real challenge. These puzzles demand advanced strategies like naked pairs, hidden singles, and X-wings.

Game Modes

Each game mode changes how many mistakes you're allowed before the puzzle ends.

• Casual: Unlimited mistakes. Good for learning and practicing without pressure (this is the default).
• Normal: You can make up to 3 mistakes before failing.
• Perfectionist: One single mistake ends the game. Only for players who are confident in every placement.

Higher-stakes modes reward more experience and more item drops, so there's a real incentive to push yourself.

Multiplayer Sudoku

Sudoku doesn't have to be a solo activity. On Foony, you can create a room and invite friends or open it up to the public. Everyone solves the same puzzle at the same time, racing to finish first.

In co-op mode, your team shares a single board and can see each other's cursors. Work together to fill in cells, divide sections among teammates, or let someone double-check your placements. Co-op is a great way to teach newer players or tackle Expert puzzles as a group.

You can also set a time limit (anywhere from 5 to 60 minutes) to keep things competitive, or leave it unlimited for a more relaxed session.

Collectible Boards and Number Styles

As you play and level up, you'll earn item drops that include custom boards and number pieces. Equip them to change the look of your puzzle grid.

Boards range from simple paper and wooden themes to rare drops like the Zen Garden Board and Ancient Scroll Board. Number styles include options like Blue Pencil, Fountain Pen, Ink Brush, and the level-50 reward Calligraphy Piece.

Some items are only available through gameplay drops at certain levels, while others can be purchased in the shop.

Sudoku Tips for Beginners

If you're new to Sudoku, these tips will help you get started.

Start with rows, columns, or boxes that are nearly full. If a row or box already has 7 or 8 numbers, figuring out the last two is straightforward. Look for the easiest wins first.

Use the pencil tool. When a cell could hold two or three possible numbers, write them down with the pencil button. As you fill in surrounding cells, you can eliminate candidates until only one remains. You probably won't need this on Easy puzzles, but it's very useful on Expert.

Scan one number at a time. Click on a number (say, 5) and check where it already appears in each row, column, and box. This often reveals cells where that number is the only option. This is my favorite strategy for solving Easy puzzles quickly.

Don't guess. Foony uses an algorithm that guarantees every Sudoku puzzle has exactly one solution, and it can always be reached through logic alone. If you find yourself guessing, take a step back and look for constraints you missed or learn advanced techniques like naked pairs, hidden singles, and X-wings.

Achievements

Earning achievements unlocks bonus rewards. Here are a few to aim for:

• First Puzzle: Solve your first Sudoku puzzle.
• Quick Solve: Finish an Easy puzzle in under 5 minutes with 3 or fewer mistakes.
• Flawless Victory: Complete any puzzle with zero mistakes.
• Hard as Nails: Solve a Hard puzzle with 3 or fewer mistakes.
• Puzzle Master: Solve an Expert puzzle with 3 or fewer mistakes.

Ready to test your logic skills? Jump into a free Sudoku puzzle and start playing.