Free Sudoku Online

What Sudoku Does

Sudoku is one of the most popular logic puzzles in the world, and finding a clean, ad-free version online is harder than it should be. Most Sudoku sites bury the grid under pop-ups, auto-playing videos, and mandatory account sign-ups before you can place a single digit. The EasyWebTools Sudoku strips all of that away and gives you the puzzle — nothing more, nothing less.

Choose from four grid sizes (4x4, 6x6, 9x9, and 16x16) and four difficulty levels (Easy, Medium, Hard, Expert) to match your skill and mood. The tool includes pencil notes for tracking candidate digits, a built-in timer to challenge yourself, full undo/redo history, and optional error checking so you can play with or without training wheels. When you finish a puzzle, generate a shareable completion card to show off your time and difficulty. Everything runs entirely in your browser — no data leaves your device, no account required, and your progress auto-saves to local storage so you can close the tab and pick up exactly where you left off.

How It Works

Each puzzle starts with a partially filled grid. Your job is to complete it using pure logic — no guessing required.

1. Pick your grid and difficulty. Select a grid size (4x4, 6x6, 9x9, or 16x16) and difficulty level (Easy, Medium, Hard, or Expert). Hit New Game to generate a fresh puzzle with a unique solution.

2. Select a cell. Click or tap any empty cell to highlight it. The row, column, and box containing that cell are subtly highlighted to help you see which digits are already placed.

3. Enter a digit. Type a number on your keyboard or tap the on-screen numpad. The digit fills the cell immediately. If you have Show Errors enabled, incorrect entries are highlighted in red right away.

4. Use pencil notes. Press N or toggle Notes mode to pencil candidate digits into a cell instead of committing a final answer. When you later place a confirmed digit, its matching notes are automatically cleared from the same row, column, and box.

5. Undo mistakes. Press Z (or Ctrl+Z) or tap the undo button to step backward through your moves. Redo is available with Y (or Ctrl+Y) to step forward again. Your full move history is preserved.

6. Pause your game. Press P or tap the pause button next to the timer. The grid is hidden while paused so nobody can peek, and the timer stops until you resume.

7. Check your work. Click the Check button at any time to highlight all incorrect cells at once, or leave Show Errors on for continuous feedback as you play.

8. Complete and share. When every cell is correctly filled, the timer stops and a completion screen appears. Download a share card as a PNG image or copy a text summary showing your grid size, difficulty, and solve time.

Why Use Our Sudoku

Sudoku belongs in your browser, not behind a paywall or buried under advertising. Here is what sets this version apart.

• Four grid sizes. Start with 4x4 to learn the rules, work through 6x6 and classic 9x9, then take on the 16x16 monster grid for a serious challenge. Most online Sudoku tools only offer 9x9.
• Smart pencil notes. Notes auto-clear when you place a confirmed digit in the same row, column, or box — saving you the tedious housekeeping that slows down paper puzzles.
• Full undo/redo history. Every move is tracked. Step backward and forward freely without worrying about losing progress. Your entire history persists across sessions via local storage.
• Optional error checking. Play purist-style with no hints, or enable real-time error highlighting to learn faster. Your choice, every game.
• Shareable completion cards. Finished a tough Expert puzzle in record time? Download a branded card or copy a text summary to flex in your group chat.

Use Cases

• Daily brain warm-up. Start your morning with an Easy or Medium 9x9 puzzle to wake up your logical thinking before diving into work or study. Five to ten minutes is all it takes.

• Learning logic fundamentals. Teachers and parents can introduce younger players to Sudoku on a 4x4 grid, then gradually increase the size as their pattern-recognition skills develop.

• Commute entertainment. Pull up a puzzle on your phone during a train ride or waiting room visit. Auto-save means you never lose progress if you need to switch apps or close the browser.

• Competitive solving. Challenge friends or family to the same difficulty and grid size, then compare completion times using the share card. The timer keeps everyone honest.

• Focus and mindfulness. Sudoku demands sustained attention without sensory overload. It is a screen-based activity that actually calms the mind — a useful break between high-stimulus tasks.

• Advanced puzzle practice. Hard and Expert difficulties on 9x9 and 16x16 grids require advanced techniques like naked pairs, hidden triples, and X-wing patterns. Pencil notes and error checking help you learn these strategies without frustration.

• Accessibility-friendly play. Full keyboard navigation, on-screen numpad, and clear visual contrast mean the game works well for players who prefer not to use a mouse or who need larger tap targets on mobile.

Tips and Best Practices

• Scan before you write. Before placing any digit, scan every row, column, and box to identify cells where only one number is possible. These “naked singles” are the safest starting moves.

• Use pencil notes liberally. On Hard and Expert puzzles, pencil notes are essential. Mark every candidate for each empty cell, then look for cells where only one candidate remains after elimination.

• Work one digit at a time. Pick a digit (say, 5) and find every row, column, and box where it already appears. The remaining positions for that digit often narrow down quickly.

• Start with the most constrained areas. Rows, columns, or boxes that are nearly full have fewer possibilities. Fill those first to create cascading solves across the rest of the grid.

• Turn off error checking for a real challenge. Show Errors is great for learning, but turning it off forces you to verify your logic independently — a more satisfying solve and better training for paper puzzles.

• Try smaller grids to learn techniques. The 6x6 grid is perfect for practicing intermediate strategies like pointing pairs and box-line reduction without the complexity of a full 9x9.

• Use undo to experiment. If you are stuck between two candidates, try one and see if it leads to a contradiction. If it does, undo back and place the other digit with confidence.

• Challenge yourself with the timer. Once you can consistently solve 9x9 Easy puzzles, start timing your Medium solves. Tracking your times over days reveals how quickly your skills are improving.