Medium Diagonal Sudoku

Both main diagonals must also contain 1–9 without repetition. Four units instead of three — twice the constraint density.

Easy Medium Hard Expert

Diagonal Sudoku at medium difficulty. Treat both diagonals as full constraint groups — hidden singles and naked pairs within each diagonal unlock the board.

4
5
3
6
4
5
8
2
6
7
8
1
6
4
3
6
8
2
5
2
8
9
1
7
8
5
6
1
3
2
3
7
Mistakes
0/3
Score
-
Time
00:00
Try Hard →
Progress0%

What is Diagonal Sudoku?

Difficulty
★★☆☆☆
2/5
Constraint Type
Extra Regions
Typical Givens
22–28
Avg. Solve (Medium)
10 min

Solving Techniques for Medium Level

Technique Description Level
Diagonal as a Unit Treat each diagonal exactly like a row or column — every digit 1–9 appears exactly once. Standard scanning and counting apply. Beginner
Diagonal–Box Interaction When a digit on a diagonal is confined to one box segment, eliminate it from the rest of that box. Intermediate
Diagonal Naked Pairs If two cells on a diagonal share the same two candidates, eliminate those values from all other diagonal cells. Intermediate

Master these, then take on Hard Diagonal Sudoku to learn Advanced techniques.

Average Solve Time by Difficulty

Easy
4 min
Medium
10 min
Hard
20 min
Expert
40 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Diagonal Sudoku →

Frequently Asked Questions — Medium Diagonal Sudoku

What techniques do I need for medium Diagonal Sudoku?
Medium puzzles require treating the diagonals as fully equal constraints alongside rows, columns, and boxes. Apply hidden singles and naked pairs within each diagonal just as you would within a row. The intersection of a diagonal with a box is especially productive for eliminations.
How does the diagonal constrain 3×3 boxes in Diagonal Sudoku?
The main diagonal passes through exactly three of the nine boxes: top-left, center, and bottom-right. Within each of those boxes, three cells are on the diagonal and those three cells must hold three different digits, also constrained to be unique across the full diagonal. This creates powerful cross-box eliminations.
What is a 'diagonal hidden single'?
A diagonal hidden single is a digit that can only go in one cell of a diagonal due to eliminations from that digit's placement in various rows and columns. Spotting these requires scanning each diagonal for candidates the same way you scan rows and boxes.
How long does a medium Diagonal Sudoku take?
Most players finish in 10–20 minutes. The extra diagonal constraints mean the board resolves faster than a standard puzzle with the same given count, so medium Diagonal puzzles are a satisfying challenge without being overwhelming.
Can the diagonal constraint create a naked pair?
Yes. If two cells on a diagonal are the only cells in that diagonal where two specific digits can go, those digits form a naked pair. You can then eliminate both digits from any other cells in those two cells' rows, columns, and boxes.

More questions? See the full Diagonal Sudoku guide.