Sudoku — fill every row, column and box with 1 to 9

How to play Sudoku

A Sudoku grid is nine rows, nine columns and nine boxes of three by three. Fill every empty square with a number from 1 to 9 so that no number is repeated in any row, any column or any box. Every puzzle here has exactly one answer, and you never have to guess to find it.

1. Tap an empty square, then tap a number to put it in.
2. Tap the same number again to take it out, or use Erase.
3. Turn on Notes to pencil in the numbers a square might hold — useful once the easy squares are gone.
4. A number that cannot be right turns red, so you always know where you stand.
5. Finish the grid and the puzzle is solved. Your time is kept for each difficulty.

Tips for solving faster

• Start where it is crowded. Look for the row, column or box that already has the most numbers — it has the fewest possibilities left.
• Hunt one number at a time. Pick 7, say, and look at every box in turn to see where a 7 can still go.
• If a square has only one candidate, it is settled. If a number can go in only one square of a box, that is settled too.
• Use notes on hard and expert. Pairs of squares that share the same two candidates rule those numbers out of the rest of the row, column or box.
• Never guess. Every puzzle here is solvable by reasoning alone.

Questions about Sudoku

Is this Sudoku free?

Yes. It is free, there is no account and nothing to install. It is paid for by the ads on the home page and on the screen shown after a puzzle is solved.

Where do the puzzles come from?

Your phone makes them. Each puzzle is generated on your own device and checked to have exactly one solution, so you get a fresh one every time and never the same grid as anyone else.

What do the four difficulties mean?

They differ in how many numbers you start with: about 44 on Easy, 36 on Medium, 31 on Hard and 27 on Expert. The fewer you are given, the more careful the reasoning has to be.

Can I play Sudoku offline?

Yes. Once the page has loaded once, it works with no internet connection — puzzles are made on your device, not fetched from a server.

Is my puzzle saved if I close the page?

Yes. Your grid, your notes and your time are kept in your browser, so you can carry on where you left off. Your best time for each difficulty is saved the same way, on your device only.

What are the notes for?

Notes are the small pencil marks solvers use to record which numbers a square could still hold. Turn Notes on, then tap numbers to add or remove them. When you place a real number, the matching pencil marks around it are cleared for you.

Do I ever have to guess?

No. Every puzzle has one solution and can be reached by logic alone.