Sudoku Online — Free Classic Number Puzzle

Play Sudoku for free online. Choose from three difficulty levels — Easy, Medium, and Hard. Fill the classic 9×9 grid using logic: each row, column, and 3×3 block must contain the digits 1 through 9 with no repeats.

How to Play

• Select a difficulty level to start a new puzzle.
• Tap or click any empty cell, then enter a number (1–9) using the numpad or keyboard.
• Fill each row, column, and 3×3 block with digits 1–9 — no duplicates allowed.
• Enable Notes mode to mark candidate numbers in cells.
• Use Undo to revert your last move if you make a mistake.
• Three wrong moves end the game — use error highlighting to avoid mistakes!

Game Features

• 🧩 Classic 9×9 Sudoku grid
• 📝 Notes mode for candidate marking
• ⏱️ Timer with best-time tracking per difficulty
• ↩ Unlimited undo (up to 50 moves)
• ❌ Error highlighting (toggle on/off)
• 📱 Touch + keyboard support
• 🎨 Three difficulty levels

Tips & Tricks

• Always check rows, columns, and blocks for missing digits before filling a cell.
• Use notes mode to track possible values — update notes as you eliminate candidates.
• If only one number can go in a cell, that's your answer.
• Look for numbers that can only go in one place within a row, column, or block.