Killer Sudoku Generator
A killer sudoku hands you no digits at all. The grid is divided into cages, each printed with the total of the digits inside it, and no digit may repeat within a cage. Everything else works as an ordinary sudoku, so the whole grid has to be reconstructed from arithmetic. That makes proving there is only one answer much harder than in a plain sudoku, where clues can simply be added until the grid is pinned down.
What this generator does
Builds a finished sudoku grid, divides it into cages that never repeat a digit, derives each cage's total, and confirms the totals admit exactly one grid before showing it.
How to use this tool
- Pick a grid size and generate a puzzle.
- Each dotted region is a cage; the small number is the total of its digits.
- No digit repeats within a cage, and the usual sudoku rules apply as well.
- Show the answer when you are done, or stuck.
Understanding the controls
- Grid size
- Four or six a side. A nine-by-nine grid with no given digits was built and measured, and confirming its answer takes longer than a page should wait.
- Seed
- A word reproduces exactly the same puzzle, so a grid can be shared or set for a group.
Common use cases
- A harder sudoku for somebody who finds the ordinary kind routine
- Arithmetic practice disguised as a puzzle
- A puzzle for a club sheet or newsletter
- A short six-by-six killer for a coffee break
- Demonstrating a puzzle proved to have exactly one answer
How this generator works
The published grid is solved again from its cages alone, counting answers rather than trusting the construction, and is only shown when the count is one. Where the totals alone leave more than one grid, a digit is given away and the count retried — then every given digit is taken back in turn, and kept only if removing it costs the puzzle its single answer. The search takes the square with the fewest possibilities at each step, since with arithmetic clues the pressure moves around the grid as it fills.
Randomness and fairness
The grid and the cage shapes come from the browser's secure generator. A seed reproduces the same puzzle exactly — that path is deterministic, not cryptographic, and exists so a puzzle can be shared.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Four and six squares a side. Nine is not offered, because confirming a single answer there needs the cage-combination reasoning a person uses rather than a square-by-square search.
- Cages hold between two and four squares, so the very large cages seen in some published puzzles do not appear.
- A digit or two may be given away where the totals alone are not enough; strictly, a killer sudoku gives none.
- Nothing here measures how hard the puzzle is; a unique answer is not an easy one.
- Cages and clues are not saved, so seed a puzzle you intend to print twice.
Privacy and your data
Puzzles are built and checked in your browser. Nothing is transmitted or stored.
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