Sudoku rules
Sudoku is a placement puzzle, not an arithmetic test. Use the digits 1 through 9 exactly once in each row, each column, and each outlined 3 × 3 box. Given numbers cannot be changed.
Start with constrained spaces
Look for a row, column, or box with many existing numbers. List what is missing, then check where each missing number can legally fit. A single legal position is a reliable next move.
Hints without an account
The included hint fills one empty square. Reset restores the original puzzle. Your entries stay in memory only until you leave or reload this page.