Sudoku X, also called diagonal sudoku, is played on the normal 9 by 9 grid. Every grid on this page is generated for you and proved to have one answer by the sudoku X solver, which also rates it by the hardest step it needs.
Rules of sudoku X
Place the digits 1 to 9 so that each row, each column, each 3 by 3 box and each of the two main diagonals contains every digit once. The diagonal squares are tinted so you can see them. The center square belongs to both diagonals, and each diagonal passes through three boxes, so a digit on a diagonal rules itself out of more squares than a digit elsewhere.
Levels
Easy grids keep 34 given digits and are rated Easy: singles alone finish them. Medium grids keep at least 26 digits and need a Medium step such as a pointing pair or a naked pair. Hard grids have as few clues as the generator could leave and are rated Hard, Expert or Master, which means X-wings, wings or chains, but never guessing. The diagonals make very sparse grids possible, so hard sudoku X often starts with fewer than 20 digits.
How to use the diagonals
- Scan each diagonal like a tenth row: which digits are missing, and where can each go?
- A digit placed on the center square counts for the middle row, the middle column, the center box and both diagonals at once.
- Where a diagonal crosses a box, the three shared squares behave like a pointing line: if a digit for that box can only sit on the diagonal, it leaves the rest of the diagonal.
- Do not forget the anti-diagonal, from the top right to the bottom left. It is the one players miss most.
Play features
Tap a square and a digit, or type on a keyboard. Pencil marks, undo and redo, Check, Show mistakes and Hint work as in our other sudoku games; the hint names the technique and the squares, including the diagonal it uses. Times and the daily streak are saved per level in your browser, and Challenge a friend shares the exact grid. Learn the shared techniques on the sudoku techniques page, or switch to classic sudoku online or jigsaw sudoku for a change.
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Questions
Is sudoku X the same as diagonal sudoku?
Yes. Both names mean a classic sudoku whose two long diagonals must also contain 1 to 9.
Does the center square count twice?
It belongs to both diagonals, its row, its column and the center box, so a digit there must fit all five.
Do the short diagonals count?
No. Only the two corner-to-corner diagonals of the whole grid are extra units.
How hard is the hard level?
Hard grids are rated Hard, Expert or Master by our solver, so they may need X-wings, wings or chains. None needs trial and error.