How to play sudoku
Fill in the grid so that every row, every column and every 3 x 3 box contains the numbers 1 to 9, each exactly once. Some numbers are given; the rest are yours to work out. There is no guessing and no maths – only logic.
- Tap a square, then tap a number below the grid – or type it.
- Not sure yet? Switch on Notes and pencil in the numbers that could go there.
- Made a mistake? Erase or Undo.
- Stuck? Hint fills in the square you selected, or a random one.
Four levels
- Easy: 40 numbers given. Most squares can be found by looking at one row, column or box.
- Medium: 33 numbers. You will start using notes.
- Hard: 28 numbers. Pairs of candidates and crossing lines.
- Expert: about 24 numbers – as few as the puzzle allows while keeping one solution.
Every puzzle is made fresh when you press New game, and every one has exactly one solution, so it can always be solved by logic alone.
Tips for solving
- Scan for singles: pick a number and look where it can still go in each box. Often only one square is left.
- Use notes from medium up: when a square has only one candidate left, that is its number.
- Pairs: two squares in a row that can only be the same two numbers take those numbers away from the rest of the row.
- Fill the fullest first: a row or box with seven numbers is two easy squares away from done.
Show mistakes marks a wrong number in red at once. Turn it off for the real challenge – then you only find out at the end.
Keyboard
On a computer, the arrow keys move around the grid, the numbers 1 to 9 fill in, Backspace erases and N switches notes on and off.
Free, in your browser
No download, no app, no account. The game runs on this page, on a phone, a tablet or a computer, and the game in progress and your best results stay on your device.