Kropki Sudoku
White dots = consecutive digits; black dots = one digit is double the other
Kropki Sudoku is fully playable. Choose a difficulty and start solving.
Black dots join cells where one digit doubles the other; white dots join consecutive digits; no dot rules out both. Dot chains such as 1-2-4-8 lock long runs of cells together. Reading the absence of dots is the skill that separates fast solvers from stuck ones.
For the complete rules, worked examples and solving techniques, read the full How to Play Kropki Sudoku guide.
Like all Sudoku variants, Kropki Sudoku builds on the classic 9×9 foundation. Every row, column, and 3×3 box must contain each digit from 1 to 9 exactly once. The variant constraint is added on top of these standard rules, never replacing them.
If you're new to Sudoku, start by learning the basic rules and techniques before attempting variants.
Techniques Useful for This Variant
| Technique | How it applies |
|---|---|
| Pencil Marks / Notes | Essential for tracking candidates alongside the variant constraint |
| Obvious Singles | Cells narrowed to one candidate by the combined constraints |
| Hidden Singles | Digits with only one valid cell in a unit after variant elimination |
| Pairs and Triples | Locked candidates exposed by the additional constraint |