Sudoku Rules: How to Play Sudoku
What is Sudoku?
Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 subgrids (also called "boxes" or "regions") contain all of the digits from 1 to 9.
The puzzle setter provides a partially completed grid, which typically has a unique solution. A properly constructed Sudoku puzzle has only one solution.
Basic Rules of Sudoku
The 3 Fundamental Rules:
- Each row must contain the numbers 1 through 9 without repetition
- Each column must contain the numbers 1 through 9 without repetition
- Each 3x3 box must contain the numbers 1 through 9 without repetition
At the beginning of the game, some cells already contain numbers, known as "givens" or "clues". These are the numbers that cannot be changed. The objective is to fill in the empty cells with numbers 1 through 9 in a way that satisfies all the rules above.
Key Points:
- You cannot repeat numbers in any row, column, or 3x3 box
- You must use numbers 1-9 only
- Each puzzle has only one correct solution
- You must rely on logic, not guessing, to solve the puzzle
- The difficulty level depends on how many clues are provided and their placement
Example:
In this example, notice how each row, column, and 3x3 box contains the numbers 1-9 exactly once:
Full grid omitted for brevity, but each row, column, and box would contain 1-9.
Difficulty Levels
Sudoku puzzles come in various difficulty levels, typically categorized as:
Easy
These puzzles have many givens (typically 35-45). Basic logic is sufficient to solve them without advanced techniques.
Medium
Fewer givens (28-34) and requires some intermediate techniques like candidate elimination.
Hard
Limited givens (24-27) and requires advanced techniques like X-Wing or Swordfish.
Expert
Minimal givens (22-23) and may require complex logic chains and pattern recognition.
The difficulty is determined not just by the number of givens, but also by their specific arrangement and the techniques required to solve the puzzle.
How to Play on Daily-Sudoku.com
Playing Sudoku on our website is simple and user-friendly:
- Select a difficulty level - Choose from Easy, Medium, Hard, or Expert depending on your skill level.
- Click on an empty cell - This selects the cell where you want to place a number.
- Enter a number - Use the on-screen number pad or your keyboard to enter a value from 1 to 9.
- Use pencil mode for notes - Enable "Pencil Mode" to make small notes in cells when you're unsure about the final value.
- Check your solution - Use the "Check" button to verify if your current entries are correct.
- Get hints when stuck - If you're stuck, you can use the "Get Hint" feature for assistance.
Remember, the goal is to fill the entire grid while adhering to the rules. The timer will keep track of how long it takes you to complete the puzzle, allowing you to improve over time.
Ready to play? Try our free Sudoku puzzles now and challenge yourself with a new puzzle every day!
Sudoku History
Sudoku has an interesting history that spans several countries:
The modern Sudoku was designed anonymously by Howard Garns, a 74-year-old retired architect and freelance puzzle constructor from Indiana, and first published in 1979 by Dell Magazines as "Number Place" (the earliest known examples of modern Sudoku).
The puzzle was introduced to Japan by the puzzle company Nikoli in April 1984. They gave it the name "Sudoku", which is short for a longer Japanese expression meaning "the digits must remain single" (数字は独身に限る, Sūji wa dokushin ni kagiru).
The puzzle became international in 2004 when Wayne Gould, a retired judge from New Zealand who had been developing computer programs to generate Sudoku puzzles, convinced The Times in London to publish them. Within months, Sudoku had become a global phenomenon.