Puzzle guide
How to play Sudoku
Fill the grid so every row, column, and 3×3 box contains the digits 1 through 9 exactly once.
Start with what is missing
Choose a row, column, or box with several filled cells. List the missing digits, then check which empty positions are blocked by the same digit elsewhere in their row or column.
Use notes for candidates
If a cell could contain more than one digit, add small candidate notes instead of guessing. As other cells are solved, remove candidates until only one remains.
Look for singles
A naked single is a cell with one possible digit. A hidden single is a digit that can appear in only one cell within a row, column, or box. These two ideas solve many beginner puzzles.