Enter numbers 1–N in each cell of the N×N grid (or click Random to generate a sample). Then click Solve. The solver will shade the correct cells black.
The solver first applies constraint propagation — unique cells (where a value appears only once in its row or column) can never be shaded. Adjacent cells to already-shaded cells cannot be shaded. Then it uses backtracking to resolve any remaining ambiguity, always checking that unshaded cells stay connected.
Three rules: no shaded cell is adjacent to another shaded cell; no unshaded number appears twice in any row or column; all unshaded cells form one connected group.
Shade cells so no number repeats in a row or column, shaded cells never touch, and the rest stay connected.
The full guide, with a worked example and common mistakes: How to play Hitori.
It places a circle — a note that a cell must stay unshaded. Long-press does the same on a phone or tablet.
No — the unshaded cells must be connected. Shaded cells must not touch at all.
Enter the numbers in the Hitori Solver grid (or press Random) and click Solve to see the shading and the reasoning.