Sudoku

Classic logic puzzle - Fill the grid with 1-9

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How to Play

Objective

Fill the 9x9 grid so that each row, column, and 3x3 box contains all digits from 1 to 9 without repetition.

Basic Controls

  • Click a cell to select it (bold numbers are given clues and cannot be changed)
  • Type a number 1-9 on your keyboard or use the number pad below the grid
  • Press Backspace/Delete to erase a cell
  • The timer starts automatically and tracks your solving time

Advanced Features

  • Notes Mode: Toggle to add pencil marks (small candidate numbers) in cells
  • Undo: Revert your last move if you make a mistake
  • Highlighting: Selected cell's row, column, and 3x3 box are highlighted
  • Error Detection: Conflicting numbers are shown in red
  • Personal Bests: Track your fastest solve time for each difficulty

Difficulty Levels

  • Easy: 40 starting clues - great for beginners and quick games
  • Medium: 30 starting clues - requires basic Sudoku techniques
  • Hard: 22 starting clues - demands advanced solving strategies

Solving Tips

  • Start by scanning rows, columns, and boxes for obvious placements
  • Use notes mode to track candidate digits in difficult cells
  • Look for "naked singles" (cells with only one possible value)
  • Eliminate candidates when you place a number in a row/column/box
  • Take your time - Sudoku rewards logical thinking over speed

About Sudoku

Sudoku is a logic-based number placement puzzle that became a global phenomenon in the 2000s. Despite its association with numbers, Sudoku is purely a logic puzzle - no math is required. The numbers could be replaced with letters or symbols without changing the puzzle.

Each puzzle has a unique solution that can be reached through logical deduction. The modern Sudoku format was popularized in Japan in the 1980s (the name means "single number" in Japanese), though similar puzzles existed earlier in French newspapers.

Our free online Sudoku offers three difficulty levels, each generated with a guaranteed unique solution. Features like pencil marks, undo, and error highlighting make it perfect for both beginners learning the ropes and experienced solvers chasing their best times.

Play Sudoku daily to improve your logical thinking, pattern recognition, and concentration. Track your progress with personal best times for each difficulty level!

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