Shade cells to eliminate duplicates. Keep unshaded cells connected. No two shaded cells can touch.
1. No number may appear more than once in any row or column (shade duplicates).
2. Shaded cells cannot be adjacent (horizontally or vertically).
3. All unshaded cells must form one connected group.
Click once to shade, twice to confirm unshaded (cyan border), third click to clear.
Hitori (Japanese for "alone" or "one") is a logic puzzle played on a grid of numbers. Your goal is to shade certain cells so that no number appears more than once in any row or column. The catch: shaded cells cannot be adjacent to each other, and all unshaded cells must remain connected in a single group. It is a pure deduction puzzle with no guessing required.
Each puzzle starts with a grid filled with numbers. Some numbers appear more than once in their row or column — these duplicates must be resolved by shading exactly the right cells. Start by identifying numbers that appear multiple times. Use the three rules (no duplicate unshaded numbers, no adjacent shading, full connectivity) to logically deduce which cells must be shaded and which must stay unshaded. The connectivity constraint is what makes Hitori uniquely challenging.
Shade cells so that no number appears more than once in any row or column. Shaded cells cannot be adjacent horizontally or vertically. All unshaded cells must remain connected in one contiguous group. Each puzzle has exactly one valid solution.
They require different skills. Hitori's connectivity constraint adds a spatial reasoning challenge that Sudoku lacks. Small Hitori grids (5x5) are approachable for beginners, but larger grids (8x8, 9x9) can be extremely challenging, rivalling the hardest Sudoku puzzles.
Use the "Check" button during gameplay. It runs a flood-fill from one unshaded cell and highlights any unshaded cells that are disconnected from the main group in red. All unshaded cells must form one contiguous group connected horizontally or vertically.
Last updated: April 2026
Hitori was first published by Nikoli, the same Japanese publisher that popularized Sudoku worldwide.