How to Play Sudoku X

Sudoku X is sudoku with two more lines to satisfy: the long diagonals.

The rules

Fill the grid with the digits 1 to 9 so that each digit appears once in every row, every column and every 3×3 box.
Each of the two main diagonals, corner to corner, also holds 1 to 9 once.

That's all. The diagonals are shaded on the grid so you don't lose track of them.

Playing on kawu

Pick a cell, then a digit. Shift + digit, or the Notes toggle, writes a small candidate.
Repeats in a row, column, box or diagonal are marked; turn on Show errors to mark digits that disagree with the solution.
Three difficulties; easy and medium can be solved with singles alone.
The daily puzzle is the same for everyone.

Next, read the Sudoku X techniques. Also on kawu: Sudoku and Killer Sudoku.

Frequently asked questions

Which cells are on the diagonals?

The nine cells from the top-left corner to the bottom-right, and the nine from the top-right to the bottom-left. The centre cell is on both. They're shaded on kawu.

Does the diagonal rule make it harder?

It makes each puzzle need fewer starting digits, but it also gives you more deductions. Many solvers find Sudoku X easier once they remember to use the diagonals.

Last updated 2026-10-20