Hitori vs Sudoku: The Puzzle Where You Erase, Not Fill

Hitori and Sudoku look like siblings. Both are Japanese number puzzles, both come from the same legendary publisher, and both live or die on the rule that a number should not repeat in a row or column. Yet the first time a Sudoku fan tries Hitori, something feels upside down, and that feeling is the key to the whole puzzle. Where Sudoku asks you to fill cells in, Hitori asks you to shade cells out. One is a puzzle of addition; the other is a puzzle of elimination. This guide compares Hitori vs Sudoku, explains that backwards mechanic, and answers the question everyone asks: is Hitori harder? Curious to feel the difference? Play a Hitori puzzle and see.

The shared DNA

Hitori and Sudoku grew up in the same house. Both were popularised by the Japanese publisher Nikoli, both are solved by pure logic with a single guaranteed solution, and both are built on the same instinct: a number should appear only once in a line. If you enjoy that satisfying click of "this number can't go here, so it must go there," you will feel at home in both.

That shared no-duplicates idea is exactly why the puzzles get confused for each other. The difference is in how you enforce it.

The big difference: fill vs erase

Here is the heart of it. In Sudoku, you start with a grid that is mostly empty, and you write numbers in until every row, column, and 3×3 box contains 1 to 9 exactly once. You are adding information.

In Hitori, you start with a grid that is completely full of numbers, and you shade some of them out (black) so that no number appears more than once, unshaded, in any row or column. You are removing information. The numbers you keep are the survivors; the duplicates get blacked out.

That single reversal, fill versus erase, changes everything about how the puzzle feels. Sudoku is about finding the one number that belongs in a gap. Hitori is about deciding which of several copies has to go. It is the same goal, "no duplicates per line," reached from the opposite direction. We dig into that elimination idea more in our piece on what Hitori means ("leave me alone" is a fitting name for a puzzle about shading away the crowd).

Two rules Sudoku doesn't have

Hitori is not just "reverse Sudoku," though. Shading cells introduces two spatial rules that Sudoku never needs:

1. Black cells can't touch. No two shaded cells may be next to each other horizontally or vertically. You can't just black out every duplicate; you have to choose which duplicate to shade so the black cells stay apart.
2. White cells must stay connected. All the unshaded cells have to form one single connected group. Shade carelessly and you can cut the grid into isolated islands, which breaks the puzzle.

Sudoku has nothing like these. They turn Hitori into a partly spatial puzzle, where you are thinking about the shape your shading makes, not just the numbers. That is a genuinely different mental workout.

Side by side

	Sudoku	Hitori
Starting grid	Mostly empty	Completely full
What you do	Fill in numbers	Shade duplicates out
Core rule	Each digit once per row, column, box	No duplicate unshaded number per row or column
Extra rules	None	Black cells can't touch; white cells stay connected
Boxes (3×3)?	Yes	No
Grid size	Fixed 9×9	Varies (5×5 up to 15×15)
Feel	Placement / addition	Elimination / subtraction, plus spatial logic

Is Hitori harder than Sudoku?

This is the most common question, and the honest answer is: it is a different kind of hard. Hitori is not objectively harder or easier, but it challenges you in ways Sudoku does not.

• The mechanic is less intuitive at first. Most people have an instinct for filling gaps, but shading away duplicates takes a few puzzles to click. That early learning curve can make Hitori feel harder.
• The spatial rules add a second layer. Keeping black cells apart and white cells connected means you are solving a logic puzzle and a connectivity puzzle at once. Sudoku has no equivalent.
• The hardest Hitori needs "what-if" reasoning. On large grids, you often assume a cell is black, follow the consequences, and shade based on whether you hit a contradiction. (This is still pure logic, not guessing, as we explain in do you have to guess in Hitori.)

Many seasoned solvers find a hard Hitori every bit as demanding as a hard Sudoku, just demanding in a different direction. If Sudoku has started to feel automatic, that difference is exactly why Hitori is such a refreshing next step.

Which should you play?

Play both, honestly. They scratch overlapping but distinct itches. Stick with Sudoku when you want the familiar comfort of filling a grid. Reach for Hitori when you want the same number-logic satisfaction with a fresh, slightly mind-bending twist, plus a spatial element Sudoku lacks. The skills transfer enough that Sudoku fans pick Hitori up quickly, but the elimination mechanic keeps it from ever feeling like "just another Sudoku."

The best way to feel the fill-versus-erase difference is to try it. Play a Hitori puzzle now, or learn the rules first if the shading mechanic is new to you.

Frequently asked questions

What is the difference between Hitori and Sudoku?

In Sudoku you fill empty cells with digits so each appears once per row, column, and 3×3 box. In Hitori you start with a full grid and shade out duplicate numbers so none repeats, unshaded, in any row or column, while keeping black cells apart and white cells connected. Sudoku is about placing numbers; Hitori is about eliminating them.

Is Hitori harder than Sudoku?

Hitori is not objectively harder, but it is a different kind of challenge. Its shade-don't-fill mechanic is less intuitive at first, and it adds two spatial rules (black cells can't touch, white cells must stay connected) that Sudoku lacks. Hard Hitori also relies on what-if reasoning, so many solvers find it just as demanding as hard Sudoku.

Is Hitori a type of Sudoku?

No. Although both are Japanese number puzzles that forbid duplicates in a line, Hitori is not a Sudoku variant. It has no 3×3 boxes, you shade cells rather than fill them, and it adds adjacency and connectivity rules. They share a publisher and a no-duplicates idea, but they are separate puzzles.

Should I play Hitori if I like Sudoku?

Yes. Hitori is a natural next step for Sudoku fans because the underlying no-duplicates logic carries over, but the elimination mechanic and spatial rules make it feel fresh. If Sudoku has become routine, Hitori offers the same kind of satisfaction with a new twist.