Sudoku

How to play Sudoku in your browser

The 9x9 grid is split into nine 3x3 boxes, and some numbers are already filled in. Your job is to fill every empty cell with a number from 1 to 9 so that no number repeats in the same row, the same column or the same box. There is no math involved: Sudoku is solved with logic, not arithmetic.

Every new game generates a different puzzle, and every puzzle has exactly one solution. You play free in the browser on your phone, tablet or computer, with nothing to download.

Five levels, from Easy to Master

The levels change more than how many numbers you start with. They also change which techniques you will usually need.

• Easy. 36 to 40 numbers given. Singles are enough.
• Medium. 30 to 35 numbers. Pointing comes into play.
• Hard. 25 to 29 numbers. You will need pairs and triples.
• Expert. 22 to 24 numbers. An X-Wing may show up.
• Master. 17 to 21 numbers. You may need a Swordfish.

Hints that teach the technique

A hint never places the number for you. It highlights one cell and tells you which technique works there: Naked Single, Hidden Single, Pointing, Naked Pair or Triple, Hidden Pair or Triple, X-Wing or Swordfish. You make the move yourself. The "Solving techniques" screen gives a short explanation of each one: how to spot it and what to do.

How many hints you get per puzzle depends on the level: 3 on Easy up to 8 on Master for free, or 5 to 12 with Premium.

Notes, mistakes and undo

• Notes mode for pencilling in candidates. When you place a correct number, it is cleared automatically from the notes in its row, column and box.
• Instant mistake check: a wrong number is marked right away. The limit is 3 mistakes; after that you can keep going without a score or start a new game.
• Highlighting: the selected cell lights up its row, column, box and every matching number on the grid.
• Undo, eraser and pause. Undo takes back your moves, but not mistakes or hints. If you switch away from the game, it pauses on its own.
• Keyboard on a computer: numbers 1 to 9, arrow keys, Backspace or Delete to erase, N for notes and Ctrl+Z (Cmd+Z on Mac) to undo.
• Your game is saved in your browser, so you can come back later and pick up where you left off.

Score and stats

The clock starts with your first move. Your score depends on the level, your time, your mistakes and the hints you use, and clearing puzzles in a row without hitting the mistake limit adds a streak bonus. In "Your records" you can see how many puzzles you have completed, your current streak, and your best time and best score on each level.

FAQ

Is it free? Do I need to download anything?
It is free and there is nothing to download. It opens in the browser on your phone, tablet or computer, and you do not need an account to play.

Which level should I start with?
Easy. Singles are all you need there, and if you get stuck, a hint shows you where to look.

Does a hint solve the puzzle for me?
No. It shows you a cell and the name of the technique; you place the number yourself.

What happens after 3 mistakes?
That puzzle no longer counts for a score. You can finish it without a score or start a new one.

Can I close the tab and finish later?
Yes. Your current puzzle is saved in your browser, so you can continue on the same device.

Can I play against someone else?
No. This is single-player Sudoku; you can compare times and scores with anyone you like.