Diagonal Sudoku
Both main diagonals must also contain 1–9
Diagonal Sudoku is fully playable. Choose a difficulty and start solving.
Both corner-to-corner lines must hold nine different digits, giving the grid two bonus houses to scan. The 17 cells they cover are the most restricted on the board, so working the diagonals first usually cracks the opening. It feels gentler than the classic game at low levels, while expert grids hide their key move on the line you forgot to check.
For the complete rules, worked examples and solving techniques, read the full How to Play Diagonal Sudoku guide.
Like all Sudoku variants, Diagonal Sudoku builds on the classic 9×9 foundation. Every row, column, and 3×3 box must contain each digit from 1 to 9 exactly once. The variant constraint is added on top of these standard rules, never replacing them.
If you're new to Sudoku, start by learning the basic rules and techniques before attempting variants.
Techniques Useful for This Variant
| Technique | How it applies |
|---|---|
| Pencil Marks / Notes | Essential for tracking candidates alongside the variant constraint |
| Obvious Singles | Cells narrowed to one candidate by the combined constraints |
| Hidden Singles | Digits with only one valid cell in a unit after variant elimination |
| Pairs and Triples | Locked candidates exposed by the additional constraint |