Expert Clone Sudoku

Shaded regions are clones — identical in digit content and position. One placement updates all its clones simultaneously.

Easy Medium Hard Expert

Expert Clone Sudoku. The hardest puzzles on the site — every placement follows from precise cross-clone and standard reasoning. No guessing.

6
8
2
8
2
4
5
1
7
6
3
9
7
1
8
5
9
5
3
8
2
4
1
7
5
9
Clone A Clone B Both regions must have identical digits
Mistakes
0/3
Score
-
Time
00:00
All Clone Sudoku Puzzles →
Progress0%

What is Clone Sudoku?

Difficulty
★★★★☆
4/5
Constraint Type
Clone Regions
Typical Givens
24–32
Avg. Solve (Expert)
72 min

Solving Techniques for Expert Level

Technique Description Level
Clone Pair Deduction Any digit placed in one clone region immediately forces the same digit in the corresponding cell of the other clone region. Beginner
Constraint Propagation A clone placement propagates through standard row, column, and box constraints in both regions simultaneously. Intermediate
Clone-Box Interaction If both clone regions share boxes with heavily constrained cells, the clone constraint rapidly resolves entire boxes. Intermediate
Mirror Elimination When a digit is eliminated from a position in one clone region by standard logic, it can be eliminated from the same position in the other clone region. Advanced
Multi-Clone Logic With two clone regions, solving either provides equal information about both. Alternate deduction paths between clones for maximum efficiency. Advanced

Average Solve Time by Difficulty

Easy
10 min
Medium
22 min
Hard
42 min
Expert
72 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Clone Sudoku →

Frequently Asked Questions — Expert Clone Sudoku

Is expert Clone Sudoku the hardest level?
Expert Clone Sudoku is the most demanding level on Sudoku.by. With very few givens, every deduction flows through the interplay of clone mirroring, standard constraints, and often multi-step chains that span both clone regions and multiple rows or columns.
Can you solve expert Clone Sudoku by guessing?
No. Every expert puzzle has a unique logical solution. Guessing in Clone Sudoku is particularly dangerous because a wrong placement in one clone corrupts both regions simultaneously, creating contradictions that can take a very long time to unravel.
What strategies are unique to expert Clone Sudoku?
At expert level, look for 'clone forcing chains': a sequence where a digit assumption in Clone A forces a value in Clone B, which forces a value in a standard box, which creates a contradiction or confirmation. Also exploit cases where both clones share a common row or column, creating double-elimination opportunities.
How do I know when to use the clone constraint vs. standard techniques?
Always check the clone constraint first after every placement. Clone propagation is a free deduction — it requires no guessing and often produces immediate placements. Only fall back to advanced standard techniques (X-Wings, Swordfish) when clone propagation is exhausted.
How long does an expert Clone Sudoku take?
Expert puzzles take most players 45–75 minutes. If you're stuck, look for an asymmetry: a cell that is heavily restricted in Clone B by external constraints but not yet resolved in Clone A. That asymmetry is usually where the breakthrough lies.

More questions? See the full Clone Sudoku guide.