Player Support

This article contains everything you need to know about Arkadium's Sudoku game. 

Use the list below to navigate specific topics about Sudoku. 

• How to play
• Menu
• Tips
• Scoring

How to play

Please watch the video below to learn more about Arkadium's Sudoku gameplay.

Difficulty level. Our free online version of web Sudoku follows in the number puzzle's classic tradition; no pen or pencil is needed! As you start the puzzle, you can choose your sudoku difficulty. 

We offer Sudoku for beginners, medium Sudoku, and Sudoku for experts:

Scanning method. The most basic technique for solving Sudoku puzzles is to use the scanning method. This involves picking a number and then looking at rows and columns across the grid containing that number. The goal is to look at all the boxes where the number can’t be placed, hopefully leaving the one box where it should be.

Scanning is especially effective when you’re looking at both rows and columns at the same time. In grids with many unfilled squares, this is often the only way to narrow down where to place a number.

This process of elimination is a fast, easy, and highly effective method to solve lower-level puzzles. Even when solving a hard puzzle, it’s a great opening move to fill in a good number of squares.

Menu

You can access the menu by clicking the icon on the top right of the screen.

In the menu, you'll have several different options to play as you like.

Use slash notes. When using notes, this option will automatically slash any numbers that you've already inserted in that specific line or space, in order to help you keep track of how many you have to go.

Auto cleanup. This option eliminates your pencil notes when necessary, without you having to manually do so.

Cleanup. Like the eraser option in the game, this option allows you to erase any notes or numbers that you've set.

Place notes. This option allows you to place notes in your board instead of the final number.

Show timer. This allows you to choose whether you'd like to see the timer or not. Please know that the timer will affect your final score regardless of whether you see it.

Show errors. This allows you to see which numbers you've placed are wrong by coloring them red.

Reveal. This lets you reveal a single cell of the puzzle, or the entire puzzle that hasn't been solved yet. You can choose this when selecting the option, as seen below. The percentage that is revealed with this option will not count towards your final score.

Print. Use this option to print your Sudoku puzzle so you can play it in real paper. Upon choosing it, you can choose whether you'd like to print the puzzle as a blank one, with your current entries, or the entire puzzle's solution, as seen below. There's no limit to how many times you can print your puzzles.

Save. You can save your current progress with this option, so that you can return to it later.

Help. If you're in need, you can use this option to check a careful explanation of the game, as well of all of the menu options available.

Reset. This option erases every number and note you've typed and allows you to start over from the beginning with a new timer.

Exit. This will exit the game, and refresh your webpage.

You also have three icons on the left which allow you to use options without having to click on the menu. The Arrow allows you to undo your last move. The Pencil allows you to take notes, and the Eraser allows you to erase any of your inserted numbers or notes.

Tips

Unless otherwise noted, these strategies apply to Sudoku, The Daily Sudoku, and The Daily Diagonal Sudoku.

1. Start Where the Grid Is Most Constrained

Begin with rows, columns, and 3×3 boxes that are already nearly complete. They require fewer eliminations and are more likely to reveal an immediate placement.

After placing a number, immediately rescan its row, column, and box. One solved cell can create several new opportunities elsewhere in the grid.

2. Hunt for Singles Before Anything Complicated

Look for Naked Singles—cells where only one number can fit—and Hidden Singles, where a particular number has only one possible position within a row, column, or box.

Another effective approach is to pick a number and scan the grid: eliminate positions blocked by existing copies until only one location remains. These simple techniques should be exhausted before moving to more advanced patterns.

3. Make Your Notes Work for You

When a cell can't be solved immediately, record every possible candidate. Keep those notes updated whenever you place a number by removing it from the relevant row, column, and box.

Accurate candidates make more advanced deductions much easier. Use Naked Pairs, Hidden Pairs, and Locked Candidates to eliminate possibilities without having to solve the affected cells immediately.

4. Escalate Your Techniques Gradually

If Singles, Pairs, and Locked Candidates aren't enough, look for more advanced patterns such as X-Wing and, on particularly difficult puzzles, Swordfish. Don't search for these patterns prematurely—they are considerably harder to spot and are often unnecessary.

If you reach a point where you feel forced to guess, step back and check your candidate notes and previous eliminations. Logical Sudoku solving should allow you to progress without relying on unsupported guesses.

5. Use diagonal intersections in Diagonal Sudoku

In The Daily Diagonal Sudoku, diagonal cells have additional restrictions that can produce solutions unavailable in standard Sudoku.

Scan each main diagonal as if it were another row or column. Look for:

• missing numbers on the diagonal;

• Naked or Hidden Singles;

• candidate pairs;

• interactions between a diagonal, box, row, and column.

When a diagonal passes through a 3×3 box, its restrictions may eliminate candidates from the other cells in that box.

6. Solve Efficiently, Not Recklessly

Use the game's tools to support your solving rather than replace it. Show Errors can identify incorrect entries, while Undo and Cleanup make it easier to recover from mistakes. Save Reveal for genuine dead ends if you're trying to preserve your score.

For regular Daily Sudoku, use easier puzzles to strengthen your fundamentals before tackling harder grids later in the week. Above all, prioritize accurate logical deductions over rushing—the timer affects scoring, but a fast mistake can create far more problems than it solves.

Scoring

General Formula: 

Final Score = Puzzle Score  * (Difficulty Bonus +  Time Bonus)

The Puzzle Score. It equals the % of the puzzle that was completed without help.