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Diagonal Sudoku (X-Sudoku)
Play diagonal Sudoku, also called X-Sudoku: classic rules plus both main diagonals must contain 1–9. Free, with a worked example.
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Diagonal Sudoku (often written X-Sudoku, for the X its two diagonals trace) keeps every classic rule and adds one more: each of the two long diagonals must also contain the digits 1 to 9 exactly once.
That single extra constraint changes how the board solves. Cells on a diagonal now belong to four units instead of three, so they are far more constrained. Diagonal-only eliminations end up being some of the most satisfying moves in the puzzle.
It's the best variant to start with: the rules are a one-line change, but the solving feels new.
Rules
- Every row contains 1–9 once.
- Every column contains 1–9 once.
- Every 3×3 box contains 1–9 once.
- Each of the two main diagonals contains 1–9 once.
Frequently asked questions
What is diagonal Sudoku?
Classic Sudoku with an added rule: both main diagonals must each contain the numbers 1 to 9 exactly once. It is also called X-Sudoku.
Is X-Sudoku harder than regular Sudoku?
The extra constraint makes diagonal cells more restricted, which can make some boards easier and others trickier — but it always adds a fresh layer of logic.
Explore more Sudoku
Try another variant, play the classic game, or sharpen up with the strategy guides.
Play classic Sudoku free →