What extra rule does Sudoku X add?

Both main diagonals must contain 1 to 9

How many groups must a center cell satisfy?

Five: row, column, box and two diagonals

If 7 is placed in a diagonal cell, what else can you do?

Remove 7 from the rest of that diagonal

What is a hidden single on a diagonal?

A digit that fits only one cell of that diagonal

Sudoku X Quiz: Diagonal Rules and Solving Tips

This Sudoku X quiz adds two extra lines of logic to the classic number grid. Play an interactive set of 10 questions on the diagonal rule, the shared center cell, how many groups each cell belongs to, extra eliminations, hidden singles on diagonals and ways to spot the X advantage early.

Start Sudoku X Quiz

🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds

Question 1 / 10 Time: 150s

Rule
What extra rule does Sudoku X add?
Cells
How many cells lie on each main diagonal?
Shared
How many cells belong to both diagonals?
Groups
How many groups must a center cell satisfy?
Units
How many units of nine does a Sudoku X grid have?
Elim
If 7 is placed in a diagonal cell, what else can you do?
Hidden
What is a hidden single on a diagonal?
Corners
Which corner cells lie on a diagonal?
Start
Where is a smart place to start in Sudoku X?
Name
Why is it called Sudoku X?

Explanations: answer key for all 10 questions

Q1: What extra rule does Sudoku X add?
Answer: Both main diagonals must contain 1 to 9
It is also called diagonal Sudoku.
Q2: How many cells lie on each main diagonal?
Answer: 9
They run corner to corner.
Q3: How many cells belong to both diagonals?
Answer: One, the center cell
It sits at row 5, column 5.
Q4: How many groups must a center cell satisfy?
Answer: Five: row, column, box and two diagonals
It is the most constrained cell.
Q5: How many units of nine does a Sudoku X grid have?
Answer: 29
27 normal units plus 2 diagonals.
Q6: If 7 is placed in a diagonal cell, what else can you do?
Answer: Remove 7 from the rest of that diagonal
Diagonals act like rows.
Q7: What is a hidden single on a diagonal?
Answer: A digit that fits only one cell of that diagonal
It works like in rows.
Q8: Which corner cells lie on a diagonal?
Answer: All four corners
Each diagonal touches two corners.
Q9: Where is a smart place to start in Sudoku X?
Answer: Cells on the diagonals
They have the most constraints.
Q10: Why is it called Sudoku X?
Answer: The two diagonals form an X
The X is often shaded.

Sudoku X Quiz – Diagonal Rules and Solving Tips

Sudoku X follows the normal rules, so every row, column and 3 by 3 box contains the digits 1 to 9. It adds one more: both main diagonals must also contain each digit once.

The diagonals form an X across the grid, and the center cell belongs to both of them. That gives the grid 29 units of nine instead of 27, and cells on the diagonals are more tightly constrained.

When a digit is placed on a diagonal, it can be removed from the rest of that diagonal. Solvers often start with diagonal cells and look for hidden singles along each line, just as in rows and columns.

What This Quiz Teaches

Puzzle fans will enjoy these questions.

What the extra rule is
Which cells are shared
How many units exist
How to make eliminations
Where to start solving

Did You Know?

Diagonal cells are often shaded in puzzle books.
Sudoku X can need fewer starting clues.
Other variants add jigsaw-shaped regions.
Killer Sudoku adds sums inside cages.
Variant puzzles keep experienced solvers challenged.