Sudoku X
Sudoku X adds one elegant twist to the classic puzzle: the two shaded diagonals that cross the grid must also contain every digit from 1 to 9. The extra rule gives you new ways to crack the grid.
How to play Sudoku X
- Fill the 9×9 grid so that every row, every column and every bold 3×3 box contains the digits 1 to 9 once each.
- The two long diagonals, shaded and marked with a thin line, must also contain each digit 1 to 9 exactly once.
- Starting digits cannot be changed. Every puzzle has exactly one solution, found by logic alone.
- Tap a square, then a number (or type it). Use Notes to pencil in candidates; placing a digit clears it from notes in the same row, column, box and diagonal.
Controls
- Arrow keys: move 1–9: enter a digit Shift + 1–9: toggle a note
- N: notes mode Backspace / 0: erase Z: undo H: hint
Tips
- Treat each diagonal like a fourth kind of unit: if eight of its squares are filled, the ninth is forced.
- The centre square sits on both diagonals, so it is one of the most constrained squares in the grid.
- Selecting a diagonal square highlights its whole diagonal, so you can see which digits it already has.
- Hard grids have fewer clues than you might expect, because the diagonals do some of the work.
FAQ
What is Sudoku X?
Sudoku X, also called Diagonal Sudoku, follows all the normal Sudoku rules and adds one more: both main diagonals must contain the digits 1 to 9 without repeating.
How do you solve a Sudoku X puzzle?
Use the usual scanning techniques, but check the diagonals as well as the row, column and box for each square. A digit on a diagonal rules that digit out of every other square on the same diagonal.
Is Sudoku X harder than normal Sudoku?
Not necessarily. The extra rule removes candidates, so a Sudoku X can start with fewer clues and still be solvable. Our Easy and Medium grids can be finished with simple singles.
Does each puzzle have a unique solution?
Yes. Every grid is created by our own generator and checked by a solver to make sure exactly one answer exists.