How to play Sudoku
- Pick a level, or Daily for today's puzzle. Click a square, then a number on the pad or your keyboard. Clues you were given are bold and can't change.
- Fill every row, column and 3 by 3 box with the digits 1 to 9, each once. Turn on Notes to pencil in the digits a square could be.
- Stuck? Hint fills in the next square that can be worked out and tells you why. Undo takes back moves one at a time.
Where to start
Look for the digit that appears most often on the board. Take each 3 by 3 box that’s missing it and check which squares the digit can still go in. When only one square in a box, row or column is left for a digit, it goes there. This is called a hidden single, and it solves most of an easy puzzle.
The second move is the naked single: a square whose row, column and box already hold eight different digits, so only one is left. Notes make these easy to see.
Using notes well
- Note only the squares you’re working on. Filling every square with notes at the start takes a long time and hides the patterns.
- Notes clear themselves. When you place a digit, it disappears from the notes in its row, column and box.
- Look for pairs. Two squares in a row that can only be 3 or 8 mean no other square in that row can be 3 or 8. That often opens up the rest.
If a puzzle has you completely stuck, the Sudoku solver solves any grid you type in, or gives you just the next step.