Fill the grid with numbers 1-9. Each row, column, and 3×3 box must contain all digits without repetition.
Fill the grid so every row, column, and 3×3 box contains digits 1-9.
Sudoku is a logic-based number placement puzzle that originated in Japan. The goal is to fill a 9×9 grid with digits 1-9 so that each column, each row, and each of the nine 3×3 sub-grids (called "boxes" or "regions") contains all digits from 1 to 9. Sudoku puzzles start with some cells already filled in, and your task is to logically deduce the remaining numbers.
Sudoku became a global phenomenon in 2004 when it started appearing in newspapers worldwide. Today, millions of people play sudoku daily as a way to exercise their brains and enjoy a relaxing mental challenge.
Learning how to play sudoku is easy, but mastering it takes practice:
Want to improve your sudoku skills? Here are proven sudoku strategies from beginner to advanced:
A naked single occurs when a cell has only one possible number. Look at a cell and eliminate all numbers already present in its row, column, and box. If only one number remains, that's your answer. This is the most basic sudoku solving technique.
A hidden single is when a number can only go in one cell within a row, column, or box, even though that cell might have other candidates. For example, if the number 5 can only appear in one specific cell in a row, that cell must be 5.
Scan rows and columns to eliminate possibilities. For each number 1-9, look at which rows and columns already contain that number. This helps identify where that number must go in adjacent boxes.
When two cells in a row, column, or box contain only the same two candidates, those two numbers can be eliminated from all other cells in that unit. For example, if two cells can only be {2, 5}, then 2 and 5 cannot appear anywhere else in that row.
Similar to hidden singles, but with two numbers. If two numbers only appear in two cells within a unit, those two cells must contain those two numbers, even if other candidates are present.
The X-Wing is a powerful advanced technique. When a candidate number appears in exactly two cells in two different rows, and those cells are in the same two columns, you can eliminate that candidate from all other cells in those two columns.
An extension of X-Wing involving three rows and three columns. If a candidate appears in exactly three cells across three rows, and those cells align in three columns, you can eliminate that candidate from other cells in those columns.
Our sudoku puzzles come in three difficulty levels:
Regular sudoku practice offers numerous cognitive benefits:
Despite its Japanese name, sudoku's origins trace back to 18th-century Switzerland. Mathematician Leonhard Euler studied "Latin Squares" - grids where each symbol appears exactly once in each row and column.
The modern sudoku puzzle was created by American architect Howard Garns in 1979, published in Dell Magazines as "Number Place." In 1984, it was introduced to Japan by Maki Kaji, who gave it the name "Sudoku" (数独, meaning "single number"). The puzzle became a global phenomenon in 2004 when Wayne Gould convinced The Times of London to publish it.
Yes! Studies show that sudoku and similar puzzles help maintain cognitive function, improve memory, and may delay the onset of dementia. Regular puzzle-solving keeps your brain active and engaged.
Easy puzzles: 5-15 minutes
Medium puzzles: 15-30 minutes
Hard puzzles: 30-60 minutes or more
Times vary greatly based on experience and the specific puzzle.
Advanced techniques like X-Wing, Swordfish, and XY-Wing are among the hardest to master. However, the most challenging puzzles often require chaining multiple techniques together and maintaining careful pencil marks throughout.
A well-constructed sudoku puzzle has exactly one solution. Puzzles with multiple solutions are considered invalid. Our puzzles are guaranteed to have unique solutions.
No! Despite using numbers, sudoku is a logic puzzle, not a math puzzle. The numbers are just symbols - you could replace them with letters or colors and the puzzle would work the same way. No arithmetic is required.
There are 6,670,903,752,021,072,936,960 (about 6.67×10²¹) valid sudoku grids. However, many of these are essentially the same through rotations and symmetries. The number of essentially unique solutions is about 5.5 billion.
If you're stuck, try these steps:
1. Re-check your pencil marks for any updates you missed
2. Look for hidden singles you might have overlooked
3. Try a different scanning approach (rows vs. columns vs. boxes)
4. Consider if you need to apply a more advanced technique
5. Take a break and come back with fresh eyes