Diagonal Sudoku
A Sudoku variation where both main diagonals must also contain 1-9
Diagonal Sudoku is a Sudoku variation that is very similar to Classic Sudoku. In addition to standard Sudoku rules, both main diagonals must also contain the digits 1-9 exactly once. Also known as X Sudoku, Extreme Sudoku, or Sudoku X, this variant adds an extra layer of constraint that makes solving more challenging and rewarding. This page contains links to all Diagonal Sudoku puzzles and its variations published on this website, including 6×6 versions and hybrid variants like Diagonal Arrow Sudoku and Frame Diagonal Sudoku.
Rules of Diagonal Sudoku
Place a digit from 1 to 9 into each of the empty cells so that each digit appears exactly once in each row, column, and 3×3 outlined box. Additionally, each of the two main diagonals must also contain the digits 1-9 exactly once.
Why Solve Diagonal Sudoku?
- Experience a classic Sudoku variant that adds diagonal constraints to standard Sudoku logic.
- Develop diagonal reasoning skills — learn to think across the entire grid along two key paths.
- Enjoy multiple difficulty levels — from beginner-friendly to very tough puzzles.
- Explore exciting variations like Diagonal Arrow, Frame Diagonal, and Diagonal Consecutive.
- Perfect for solvers of all skill levels — available in both 9×9 and 6×6 formats.
- A great entry point into Sudoku variants with diagonal constraints.
Key Techniques for Solving Diagonal Sudoku
- Apply standard Sudoku logic — start with rows, columns, and boxes just like Classic Sudoku.
- Track both main diagonals — each diagonal must contain 1-9 exactly once.
- Use diagonal eliminations — once a digit is placed on a diagonal, it cannot appear again on that diagonal.
- Look for diagonal pairs and triples — the same techniques that work in rows and columns also work on diagonals.
- Check your diagonal sets — verify that each diagonal contains all digits 1-9 once.
- Combine with variant rules — for hybrid variants, apply both Diagonal Sudoku and the additional constraints simultaneously.
❌ 9×9 Diagonal Sudoku Puzzles
❌ 6×6 Diagonal Sudoku Puzzles
❌ Diagonal Sudoku Variations
❌ Diagonal Arrow Sudoku
Arrow Sudoku Rules apply. Additionally, each marked diagonal must also contain digits 1-9 only once.
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Frequently Asked Questions
What is Diagonal Sudoku?
Diagonal Sudoku is a variation of Classic Sudoku where, in addition to standard rules, the two main diagonals must also contain the digits 1-9 exactly once. It is also known as X Sudoku, Extreme Sudoku, or Sudoku X. The diagonal constraint adds an extra layer of logic to the puzzle.
What sizes of Diagonal Sudoku are available?
This collection includes both 9×9 and 6×6 Diagonal Sudoku puzzles. The 6×6 puzzles are perfect for beginners and younger solvers, while the 9×9 puzzles offer more challenging puzzles for experienced solvers.
What are Diagonal Sudoku Variations?
This collection includes several exciting variations: Frame Diagonal Sudoku (combines Frame Sudoku with Diagonal Sudoku), Diagonal Arrow Sudoku (combines Arrow Sudoku with Diagonal Sudoku), Diagonal Consecutive Sudoku, Double Diagonal Sudoku, Argyle Sudoku, and Diagonal Thermo Sudoku. Each variant adds unique constraints to the diagonal rule.
Where can I find more Sudoku variants?
The Sudoku Variations Main Page is the central index for all Sudoku variant types available on Fun With Puzzles. It covers a wide range of constraint-based variants and is the best place to discover new Sudoku challenges.
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