Play Sudoku free in your browser.
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Hard puzzles have fewer starting numbers and need techniques beyond single placements. Expect to spend time with your notes, looking for patterns that remove candidates.
Hard Sudoku techniques
- Look for naked pairs: two cells in a row, column, or box with the same two candidates. Those numbers can be removed from the rest of that unit.
- If a number in a box can only sit in one row or column, remove it from that row or column outside the box.
- Undo is free. Hints are recorded in your result, so save them for when you are truly stuck.
How to play & game info
Play Sudoku online
Nine numbers. One little escape. Find your pace with five difficulties, fresh seeded puzzles, and a friendly challenge to share.
Saves stay in this browser. Clearing site data removes them.
How to play Sudoku
- Fill each row, column, and 3 × 3 box with the numbers 1–9, using each number exactly once. Every puzzle has one solution.
- Choose Beginner, Easy, Medium, Hard, or Expert. Each fresh puzzle is generated in your browser, with difficulty based on the solving techniques it requires.
- Touch or click a cell, then use the number pad. Keyboard: arrows move, 1–9 enter a number, Delete or Backspace erases, and N toggles pencil notes.
- Notes track possibilities. Placing a number clears matching notes in its row, column, and box. Undo, or Ctrl/Cmd+Z on the board, restores your previous move.
- Conflicting numbers show an exclamation mark. A Hint reveals one correct number; the number of hints stays recorded even if you undo it.
- P pauses or resumes; Escape pauses. The timer stops and the board is hidden during a break. Progress saves in this browser, including notes and time, so you can resume later.
- Share a puzzle at any time, or choose Challenge a friend after finishing to include your time and hints. The link opens the same puzzle with your friend's own timer and your time to beat. Shared times work on an honour system.
Sudoku tips
- Start with rows, columns, or boxes that are almost complete. A number may have only one place to go.
- Select a filled cell to highlight its number across the board. The selected cell's row, column, and box are shaded.
- Use Notes to track candidates, then look for numbers that share the same two cells. Your notes and undo history save with your puzzle.
- Try Beginner or Easy before moving up. Hard and Expert require more involved reasoning, rather than simply more empty cells.
Questions about Sudoku
How do Sudoku challenge links work?
A compact puzzle code includes the generator version, difficulty, and seed. Your friend gets exactly the same starting grid. After you finish, the shared link also includes your elapsed time and hints, giving them a time to beat. No account is needed; shared results work on an honour system.
Will I see the same Sudoku again?
Fresh puzzles use a large random seed space, making accidental repeats very unlikely. Webcade also remembers the latest 128 starting grids in this browser and rejects exact repeats when creating a new puzzle. Opening a shared link intentionally replays that puzzle. Clearing browser data removes the recent history.
Does Sudoku save my puzzle?
Yes. Your current puzzle, numbers, pencil notes, undo history, hints, and timer save in this browser when storage is available. Resume explicitly when you return. Starting a new puzzle replaces that saved progress; saves do not sync between devices.
Can I play Sudoku offline?
Yes, after Webcade has finished downloading for offline play. Puzzles are generated on your device. Already-downloaded challenge links work offline too; sending the link to someone still requires your usual messaging connection.
Can I play Sudoku offline?
Yes, after loading Webcade online and waiting for “Ready for offline play”. The arcade must finish downloading its assets before offline play is available.
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