Notes mark every number a cell could still be. When you place a number, it is cleared from the notes of every cell in its row, column and box.
Notes are small marks you add to an empty cell to record which numbers it could still be.
How to use them
- Turn on Notes (or press N), then choose a number to add it to the selected cell. Choose it again to remove it.
- Notes can only go in empty cells. Placing a real number in a cell clears that cell's own notes.
They clean themselves up
When you place a number, the game removes that number from the notes of every other cell in the same row, column and 3×3 box. You do not have to rub them out, and new single-candidate cells appear as you go.
When to use them
Easy puzzles often fall to scanning alone. On Medium and Hard, notes make it far easier to spot pairs and singles; the Sudoku solving techniques guide shows how. Notes are also part of undo.
New to the grid? Start with how to play Sudoku.