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Kropki Sudoku
Play Kropki Sudoku: classic rules plus white dots (consecutive) and black dots (2:1 ratio) between neighbouring cells. Free, with difficulty levels.
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Kropki Sudoku decorates the edges between neighbouring cells with small dots. A white dot means the two cells are consecutive — they differ by exactly one. A black dot means one cell is exactly double the other.
There is a twist that makes Kropki so elegant: the absence of a dot is information too. If two neighbours have no dot between them, they are neither consecutive nor in a 2:1 ratio. Skilled solvers read the empty edges as carefully as the marked ones.
Because the dots pin down so much, Kropki boards often start with very few given digits — the relationships do the work. Pick a difficulty and Playoku deals a fresh, uniquely-solvable board.
Rules
- All classic Sudoku rules apply.
- A white dot between two cells means they are consecutive (differ by 1).
- A black dot means one cell is exactly twice the other.
- No dot between neighbours means they are neither consecutive nor in a 2:1 ratio.
Frequently asked questions
What do the dots mean in Kropki Sudoku?
A white dot marks consecutive neighbours (differ by 1); a black dot marks neighbours in a 2:1 ratio (one is double the other).
What does it mean when there is no dot?
A missing dot is a real clue: those two neighbouring cells are neither consecutive nor in a 2:1 ratio. This "negative constraint" is central to solving Kropki.
Explore more Sudoku
Try another variant, play the classic game, or sharpen up with the strategy guides.
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