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Sudoku is a grid of 81 squares split into nine boxes. Some squares already have a number. Your job is to fill in the rest so that every row, every column and every box holds the numbers 1 to 9 once each.
There is no maths involved. You never add anything up. It is a puzzle about where things can and cannot go, and every puzzle on this page can be solved by reasoning alone, without guessing. Pick a level and a new puzzle appears straight away.
How to play
Pick a square, then a number
Click or tap an empty square, then press a number on the pad or on your keyboard. The row, the column and the box of the square you picked are shaded, so you can see at a glance which numbers are already used.
Use notes when you are not sure
Turn on Notes to pencil in the numbers a square could still hold. On Easy you will rarely need them. From Hard upwards they are how you keep track of the board.
Wrong numbers show in red
A wrong number turns red and the squares it clashes with are marked. Three mistakes ends the game, so on harder levels it is worth checking before you commit.
Stuck? Take a hint
A hint fills in the square you have selected. With nothing selected, it fills the square with the fewest options left, which is usually the next one a good solver would find.
New to the game? The full guide to playing Sudoku starts from the very beginning.
Six levels, from Easy to Extreme
The difference between levels is how many numbers you start with. Fewer numbers means you have to work harder to find each next step.
Easy
Lots of numbers to start with. You can solve it by looking along rows, columns and boxes.
Medium
Fewer numbers. You will spend more time finding the one cell where a number has to go.
Hard
Notes start to pay off here. Look for pairs of cells that share the same two options.
Expert
Needs a plan. Pointing pairs and box and line checks do most of the work.
Master
Very few numbers. Expect to use notes on most of the board and to find an X-Wing now and then.
Extreme
The fewest numbers we can leave while keeping one answer. For people who like a long fight.
Keyboard shortcuts
On a computer you can play without touching the mouse.
| Move around | ← ↑ → ↓ |
|---|---|
| Enter a number | 1 to 9 |
| Clear a square | Backspace or Delete |
| Notes on or off | N |
| Undo | Z or Ctrl + Z |
| Hint | H |
| Pause | P |
Questions people ask
Is this Sudoku free?
Yes. Every puzzle is free to play in your browser. There is no account, no download and no limit on how many games you play.
Does every puzzle have only one answer?
Yes. Each puzzle is checked by a solver before you see it. If a puzzle could be finished in two different ways, it is thrown away and a new one is made.
How do notes work?
Turn on Notes and the numbers you type go into the cell as small reminders instead of answers. Tap the same number again to remove it. When you place a correct answer, that number is cleared from the notes in the same row, column and box.
What happens after three mistakes?
The game ends. You can try the same puzzle again from the start, or begin a new one. Undo does not bring back a lost game, so take your time on the hard levels.
Will I lose my game if I close the page?
No. Your progress is saved in your browser after every move. Open the page again on the same device and the puzzle is where you left it.
How is the score worked out?
Each correct number earns points, with a bonus for several correct numbers in a row. Harder levels are worth more. A mistake costs 20 points and a hint costs 15.
Keep going
How to play
The rules, the words people use, and your first moves.
Strategy
From hidden singles to X-Wings, one technique at a time.
History
An American puzzle with a Japanese name and a British boom.
Mini Sudoku
A 6 by 6 grid. Good for a coffee break or for learning.
Blog
Short reads about puzzles, solving and how this site works.