Diagonal Sudoku
Both main diagonals must also contain 1–9
Diagonal Sudoku is fully playable. Choose a difficulty and start solving.
In Diagonal Sudoku, the standard 9×9 rules apply — but with one powerful extra constraint: both main diagonals (top-left to bottom-right, and top-right to bottom-left) must each contain every digit from 1 to 9 exactly once. This extra constraint typically makes the puzzle easier to solve since diagonals act as two extra units for elimination.
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 |