Nurikabe Puzzle Generator
Nurikabe sets two rules against each other. Each number must sit in an island of exactly that many squares, and no two islands may touch — that part is local, and you can reason about it a number at a time. Everything not in an island is wall, and the wall must be one connected piece with no two-by-two block anywhere — that part is global, and it constantly overrules what the numbers alone would allow.
What this generator does
Grows the wall one square at a time, refusing any square that would close a two-by-two block, then numbers whatever pockets of white are left and confirms the numbers admit exactly one answer.
How to use this tool
- Pick a grid size and generate a puzzle.
- Shade the squares that form the wall, leaving islands unshaded.
- Each number must end up in an island of exactly that many squares, and islands must never touch.
- Check the wall is one connected piece and contains no two-by-two block.
Understanding the controls
- Grid size
- From five squares a side to seven. Eight was built and measured as well, but the slowest grid took over a second to confirm, so it is not offered.
- Seed
- A word reproduces exactly the same grid, so the same puzzle can be set for several people without passing the picture around.
Common use cases
- A logic puzzle that rewards thinking about connectivity
- Puzzle content for a club sheet or newsletter
- Practice at reasoning where local and global rules conflict
- Demonstrating a puzzle that is proved to have one answer
- A change from number-placement puzzles
How this generator works
Solving works by shape rather than by square: for each number, every island of that size containing it is enumerated, and combinations are tried that leave the islands apart. The leftover squares are then tested for connectivity and for two-by-two blocks. Counting stops at two answers, and a grid is published only when the count is one.
Randomness and fairness
The wall is grown at random within the rules. A seed reproduces the same grid exactly, which makes that path deterministic, not cryptographic — anyone with the seed can rebuild the puzzle. Without a seed, the browser's secure generator is used.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Grids stop at seven squares a side, a ceiling set by how long confirming a single answer takes.
- Islands are capped at five squares, so very large islands never appear.
- Difficulty is not graded, and a small grid can still be awkward.
- No hints or partial checking — the answer is revealed whole.
- The grid is gone once you leave; the seed is the only way back to this particular one.
Privacy and your data
Every grid is generated and checked inside your browser. Nothing about a puzzle or its answer leaves the device.
Related generators
- Tapa Puzzle GeneratorPrints a Tapa grid where each clue counts the runs of shaded squares around it, with exactly one wall that fits.
- Light Up Puzzle GeneratorAkari grids where every square must be lit, no bulb may light another, and only one arrangement works.
- Hitori Puzzle GeneratorShade out the repeats without letting two shaded cells touch or the rest come apart, with a single answer proved by construction and by search.
- Slitherlink Puzzle GeneratorPrintable Slitherlink loop puzzles with every clue proved necessary and exactly one closed loop satisfying them.