Rules
The diagonals are full Sudoku units.
Rows, columns, and 3×3 boxes still use 1–9 once. The two shaded diagonals do too. Their center square belongs to both diagonals.
Sudoku X · free online
Diagonal Sudoku
Two shaded diagonals add just enough pressure to change every solve. Use normal Sudoku rules, then make sure each corner-to-corner line also contains 1–9 once.
- Grid
- 9×9
- Extra units
- 2 diagonals
- Solutions
- Exactly 1
Strategy
Scan the X after every placement.
A number removed from a row may leave only one place on a diagonal. Treat each shaded line like an extra row and revisit it often.
Also called
Diagonal Sudoku and Sudoku X.
Both names describe the same common rule set. This board was checked against all standard and diagonal constraints and has one solution.