Sudoku Guide
Sudoku Strategies and Tips
Good Sudoku solving is about reducing possibilities logically rather than guessing.
Naked singles
A naked single is an empty cell where only one number is possible after checking its row, column, and box.
Hidden singles
A hidden single occurs when a particular number can go in only one cell within a row, column, or 3×3 box, even if that cell has other candidates.
Use pencil marks
For harder puzzles, record possible numbers in empty cells. Whenever a number is confirmed, remove it from related candidates.
Don't guess
When stuck, revisit the grid and look for relationships between candidates. A logical next step is usually created by something you placed earlier.