Diagonal Sudoku (X-Sudoku)
Classic sudoku plus a constraint on both main diagonals.
What is diagonal sudoku (x-sudoku)?
Diagonal sudoku. sometimes called X-sudoku. adds two extra constraints to classic sudoku: both the top-left-to-bottom-right and top-right-to-bottom-left diagonals must each contain digits 1 through 9 exactly once. Those extra constraints make for tighter logic and fewer starting clues.
Rules
- Standard 9×9 sudoku rules apply.
- The main diagonal (top-left to bottom-right) contains each digit 1–9 exactly once.
- The anti-diagonal (top-right to bottom-left) contains each digit 1–9 exactly once.
Tips
- Track diagonals as you would a row or column. they're extra elimination groups.
- The centre cell (r5, c5) sits on both diagonals, so digits there cascade widely.
- When stuck, check whether either diagonal is missing only one or two digits.
Related variants
- Hyper Sudoku, Classic sudoku with four extra 3×3 regions to satisfy.
- Jigsaw Sudoku, Sudoku with non-rectangular regions. same digit constraint, weirder shapes.
- Consecutive Sudoku, Classic sudoku with markers showing which adjacent cells differ by exactly one.
- Classic sudoku for comparison
Diagonal Sudoku (X-Sudoku) FAQ
What is X-sudoku?
X-sudoku is another name for diagonal sudoku: a 9×9 sudoku with the added constraint that both main diagonals also contain digits 1–9 exactly once.
Is diagonal sudoku harder than classic?
Slightly harder for a given clue count, but easier to solve at a fixed difficulty rating. the extra constraints provide more elimination paths.
Do both diagonals always have the constraint?
In standard diagonal sudoku, yes. Some variants only constrain one diagonal. Sudokly uses both.
Can I solve diagonal sudoku with classic techniques?
Mostly. The extra diagonals mean hidden singles often appear there first. always scan them.
Are diagonal puzzles unique?
Yes. Uniqueness is verified during generation.