Hitori Puzzle Generator
Three rules that pull against each other: no number may repeat in a row or column once the shading is done, no two shaded cells may touch edge to edge, and everything left unshaded must stay in one connected piece. The third rule is the one people forget, and it is what makes a shading that fixes every duplicate still wrong. Every grid here is proved to have exactly one valid shading.
What this generator does
Chooses the shading first and then fills in numbers that make it necessary: unshaded cells take a Latin square so no repeats survive, and shaded cells copy a value from their own row or column so that leaving them unshaded would break a rule.
How to use this tool
- Choose the grid size.
- Shade cells until no number repeats in any row or column.
- Check that no two shaded cells touch and the unshaded cells are still joined up.
- Reveal the answer, or seed the grid to set the same puzzle again.
Understanding the controls
- Grid size
- Between 4 and 9. Nine takes around a tenth of a second including the uniqueness proof, which is what sets the ceiling.
- Seed
- Reproduces the same grid exactly, which is what a printed or shared puzzle needs.
- Show the answer
- Fills in the shaded cells, so the three rules can be checked against the finished grid.
Common use cases
- A logic puzzle with no arithmetic at all
- Practice at the connectivity rule, which is where most attempts fail
- Printable grids with a guaranteed single answer
- A short puzzle that takes minutes rather than an evening
- Testing a shading solver against verified grids
How this generator works
The shading is built as a maximal independent set: no two shaded cells touch, and no unshaded cell could be shaded as well. That maximality is what makes the puzzle unique — shading an extra cell can never create a duplicate, so without it any legal extra shading would be a second answer. An exhaustive search then confirms no other shading works at all.
Randomness and fairness
The shading pattern and the numbers are random; the single answer is proved by search. Seeded puzzles reproduce exactly and are therefore explicitly not cryptographically secure. Unseeded, the browser's cryptographically secure generator supplies the draws.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Grids are square and stop at nine, which is smaller than many published Hitori puzzles.
- Numbers run from one to the grid size, so the wider ranges some puzzles use do not appear.
- Difficulty is not graded — uniqueness is proved, but nothing measures how hard the deduction is.
- There is no interactive shading; the answer is revealed rather than entered.
- Puzzles are not stored between visits, so seed anything you intend to print.
Privacy and your data
Grids are generated and solved in your browser. No seed, puzzle or solution is transmitted or retained.
Related generators
- Shikaku Puzzle GeneratorCut the grid into rectangles, one number in each, that number being its area — with the single answer proved before you see it.
- KenKen GeneratorArithmetic-cage puzzles on a Latin square, every one solved exhaustively to prove it has exactly one answer.
- Nonogram GeneratorPrintable nonograms whose clues are proved to have exactly one solution, and to be solvable without guessing.
- Minesweeper GeneratorPrintable Minesweeper boards proved finishable from the numbers alone, so no square is ever a coin flip.