ToolAdda
🧩 Puzzle Game 4 Levels 📝 Notes 📅 Daily

Play Sudoku Online

Four difficulty levels, notes, hints, undo/redo, and a daily challenge. Every puzzle is solver-verified with exactly one solution.

🎯 Random 📊 Medium ⏳ Loading puzzle…

Number pad

Entry tools

Game tools

Play Sudoku Online — Free Puzzle Game

Play free Sudoku online with unlimited puzzles, four difficulty levels, pencil notes, hints, and a daily challenge. Every board is solver-verified to have exactly one solution — no dead ends, no ambiguous guesses. Your progress, timer, and stats save locally in your browser with no sign-up required.

How to play

  1. Choose Random, Continue, or Daily Challenge.
  2. Select difficulty: Easy, Medium, Hard, or Expert.
  3. Click a cell and enter numbers 1–9 using the pad or keyboard.
  4. Use Notes for pencil marks and Hint when stuck.
  5. Complete the grid with no repeats in any row, column, or 3×3 box.

Why play here?

  • 100% free — no ads, no account, no download.
  • Four levels — Easy to Expert for all skill levels.
  • Smart tools — notes, hints, undo, redo, validate.
  • Daily puzzle — same challenge for everyone each day.
  • Private — everything runs locally in your browser.

Sudoku rules

  • Fill the 9×9 grid with digits 1 through 9.
  • Each row must contain all digits 1–9 exactly once.
  • Each column must contain all digits 1–9 exactly once.
  • Each 3×3 box must contain all digits 1–9 exactly once.

Difficulty guide

  • Easy — most starting clues, great for beginners.
  • Medium — balanced challenge for regular players.
  • Hard — fewer clues, needs careful deduction.
  • Expert — fewest clues, advanced logic required.

Tips to solve faster

  • Scan rows and columns for numbers that can only fit one cell.
  • Use Notes mode to track candidates in Hard puzzles.
  • Look for naked pairs and singles within 3×3 boxes.
  • Use Check Move before committing a risky guess.

Keyboard shortcuts

  • Arrow keys / WASD — move between cells.
  • 1–9 — enter a number in the selected cell.
  • Works on desktop and mobile with touch controls.

Frequently asked questions

What are the rules of Sudoku?

Fill the 9×9 grid so every row, column, and 3×3 box contains digits 1–9 exactly once with no repeats.

Is every puzzle guaranteed to have a solution?

Yes. Every puzzle is verified with a solver to have exactly one valid solution before you play.

What is the difference between Easy, Medium, Hard, and Expert?

Difficulty controls how many starting clues remain. Easy has the most given numbers; Expert has the fewest and requires advanced deduction.

How do notes (pencil marks) work?

Turn on Notes mode and tap a number to add small candidate marks in a cell. Turn Notes off to place final answers.

Can I continue a game later or play a daily challenge?

Yes. Continue Saved Game picks up where you left off. Daily Challenge gives everyone the same puzzle each day.

Is this Sudoku game free?

Yes. ToolAdda Sudoku is completely free with unlimited puzzles and no sign-up required.

Is my progress uploaded anywhere?

No. Your board, moves, notes, and statistics are stored only in your browser's local storage.