Sudoku

Did you know Sudoku can actually keep your brain younger? A 2019 study published in the International Journal of Geriatric Psychiatry found that adults who regularly play number puzzles possess the brain function of someone up to 10 years younger. Originally invented in 1979 by Howard Garns as 'Number Place', the puzzle exploded globally after Maki Kaji popularized it in Japan under the name Sudoku. The game presents a 9x9 grid divided into nine 3x3 boxes. You must fill every cell so that each row, column, and box contains the digits 1 through 9 exactly once. It requires zero math skills—only logic and deduction. Challenge your brain and play our browser-based version today.

1. Look at the partially filled 9x9 grid. The provided numbers serve as your starting clues.
2. Fill every empty cell with a single digit from 1 to 9.
3. Ensure each horizontal row contains the numbers 1 through 9 without repeating any digit.
4. Ensure each vertical column contains 1 through 9 without repeating.
5. Check that each of the nine 3x3 boxes contains 1 through 9 without repeating.
6. Use logic to eliminate possibilities. Never guess.

• Rows must contain digits 1 through 9 exactly once.
• Columns must contain digits 1 through 9 exactly once.
• 3x3 boxes must contain digits 1 through 9 exactly once.
• A properly constructed puzzle has exactly one unique solution.
• You cannot change the original clue numbers.
• You do not need to add or multiply the numbers.

• Find rows, columns, or boxes that already contain five or more numbers. These offer the easiest starting points.
• Use cross-hatching. Scan the grid for the number 1, then check where a 1 can fit in a specific 3x3 box based on intersecting rows and columns.
• Look for naked singles. When a cell's row, column, and box collectively contain eight different digits, the remaining digit must go in that cell.
• Track your candidates. Write small pencil marks in empty cells to track which numbers can logically fit there.
• Search for hidden singles. If a number can only fit in one specific cell within a row, place it there, even if that cell has other candidates.

• Killer Sudoku: Combines standard rules with arithmetic. Cells form cages that must add up to a specific total.
• Mini Sudoku (4x4 or 6x6): Smaller grids designed for absolute beginners to learn basic deduction techniques.
• Diagonal Sudoku: Adds a rule where the two main diagonals must also contain the numbers 1 through 9 without repeating.

• The game provides a clear, objective right answer.
• Solving a difficult grid offers a massive sense of accomplishment.
• It requires deep focus, blocking out external stress.
• You can pause and resume the same puzzle throughout the day.

Play Sudoku free in your browser. Select from Easy, Medium, Hard, and Expert difficulties. Our interface includes pencil marks, auto-checking, hints, and mistake highlighting to help you learn. Every puzzle guarantees a single, logical solution.

Sudoku trains your brain to recognize patterns and process information systematically. It offers an excellent daily mental workout. Pick your difficulty level and start solving today.

• Sudoku and Brain Health - International Journal of Geriatric Psychiatry
• Howard Garns and the History of Sudoku