Overview

Hitori

1 player · 5-20 min per session

Shade (blacken) some cells so that no number repeats in any row or column, shaded cells don’t touch orthogonally, and all unshaded cells stay connected.

Players: 1P Session length: 5-20 min

PuzzleNumber

Goal & Core Rules

Shade (blacken) some cells so that no number repeats in any row or column, shaded cells don’t touch orthogonally, and all unshaded cells stay connected.

In each row and column, each number must appear at most once among unshaded cells.
Shaded (black) cells may not be adjacent orthogonally (up/down/left/right).
All unshaded cells must form a single orthogonally connected group.
You may shade any cell, as long as all rules remain satisfied.

Classic

Standard Hitori rules.

Easy

5x5 to 12x12 easy boards for learning the rules and basic patterns.

Tricky

The same board sizes with denser duplicate patterns and longer deduction chains.

Controls

Mouse

Left click: apply the current input mode
Right click: toggle a circle note on the cell
Use the top menu for hint, new game, and help

Keyboard

This implementation does not currently provide dedicated keyboard shortcuts.

Touch

Tap: apply the current input mode
Long-press: toggle a circle note
Use the bottom/right Black Cell and Circle buttons to switch modes
Use pinch zoom plus scrolling for larger 10x10 or 12x12 boards

Beginner Tips

Start with the most duplicated numbers in a row/column—they usually produce forced shades.
Watch the ‘no-adjacent-shades’ rule: it often forces neighboring cells to stay unshaded.
Continuously check connectivity so you don’t accidentally isolate a ‘white island’.

Advanced Tips

Use connectivity proactively: if shading a cell would split the remaining whites into islands, it’s impossible.
Look for patterns where two duplicates ‘pin’ a middle segment, forcing which one must be shaded.
Work back and forth between duplicates and connectivity constraints—each unlocks the other.

Origins & History

Hitori is an original puzzle type published by the Japanese puzzle company Nikoli. It first appeared in Puzzle Communication Nikoli issue #29 in March 1990.

Timeline

1990 First published by Nikoli in Puzzle Communication Nikoli #29 (March 1990).

Notable People

Nikoli Japanese puzzle publisher credited with originating Hitori as a puzzle type

Trivia

‘Hitori’ (ひとり) literally means ‘alone’ in Japanese—reflecting the puzzle’s solitary play.

Sources

Hitori — Wikipedia

FAQ

Do diagonally touching shaded cells break the rules?

No. Only orthogonal adjacency (up/down/left/right) is forbidden for shaded cells.

What’s the most common mistake?

Forgetting the connectivity rule and accidentally leaving unshaded cells split into separate islands.

How do I get unstuck without guessing?

Re-check duplicates in the most constrained row/column and test whether a candidate shade would violate connectivity.