Summary: Hitori is a Japanese number-logic puzzle where you shade cells out until no number repeats in any row or column. This guide explains the goal, the three rules, and how to start solving.
Overview
Hitori is a logic puzzle played on a square grid of numbers. The name is Japanese for “alone” — which is exactly what every surviving number ends up being in its own row and column.
Every grid starts completely full. There are no empty squares to fill in, and one move is all you get: shade a cell out, or leave it alone.
Look at the two boards above. On the left, every cell holds a number and several numbers repeat in the same row or column. On the right, some cells have been shaded black, and the numbers still showing are all different within their row and within their column. That transformation is the whole puzzle.
What Is the Goal of Hitori?
Shade cells until every number still showing is unique in its row and in its column — with no two shaded cells touching edge to edge, and all the white cells still joined together in one region. The numbers are the clues; the shading is your answer.
The Three Rules
1. No number repeats among the white cells. In every row and every column, each number may appear at most once among the cells you leave white. A repeated number is only allowed if one of the pair has been shaded away.
2. Shaded cells never touch edge to edge. No two shaded cells may share a side. They may touch at the corners — diagonal contact is perfectly legal, and both solved grids on this page contain diagonal runs of black cells.
3. The white cells stay in one piece. Every white cell must connect to every other white cell by a path of white cells running up, down, left or right. You may never shade a cell in a way that seals off another white cell, or splits the white area into two islands.
That third rule is the one beginners forget, and it does real work: a shading can satisfy the first two rules perfectly and still be wrong because it strands a white cell. You will see exactly that happen in the walkthrough below.
Every Hitori puzzle Puzzle Maker Pro generates has exactly one solution, and every one can be reached by pure reasoning — you never have to guess and back up. Better still, the four core moves below are all you ever need — if you are stuck, one of them applies somewhere on the board. (The adjacent-pair spot that opens the walkthrough is a handy shortcut, not a fifth rule.)
How to Start Solving
Work on the small board below — 5 × 5, the gentlest size. The grid on the right is the finished answer, so cover it with your hand and only check at the end. Rows and columns are numbered along the edges.
Before you start, give yourself a way to record what you have worked out: pencil a small dot in each cell you have proved white, and fill in the ones you have proved shaded. The chain below depends on remembering what is already settled.
Warm up by spotting adjacent pairs. When two identical numbers sit side by side, exactly one of them is shaded — never both (they would touch) and never neither (they would repeat). Row 1 reads 3 2 1 4 4, so one of those two 4s is black. You do not know which yet, but you do know that between them they use up the row’s only white 4 — so any other 4 in row 1 could be shaded on sight. This row has just those two, so nothing to mark yet; on bigger boards this fires constantly.
Then find a sandwich — this is the move that gives you a certainty. When a number sits directly between two copies of the same number, the middle cell must stay white. Row 3 reads 1 3 4 2 4, and the 2 at column 4 sits between a 4 and a 4. Why must it be white? Because if you shaded it, rule 2 would force both its neighbours white — and two white 4s in the same row breaks rule 1. So the 2 stays white.
This is the most useful pattern in Hitori. Hunt for it both horizontally and vertically. There is a vertical one on this board too: in column 5, the 1 at row 2 is sandwiched between a 4 above and a 4 below, so it must stay white. That 1 has no twin anywhere in its row or column, so park it for now — it costs nothing to know.
Now let each white cell shade its twins. Once a cell is proved white, every other cell holding that same number in its row and column must be shaded. Your white 2 sits at row 3, column 4 — and column 4 holds another 2, at row 4. So row 4, column 4 is black.
Then let each shaded cell whiten its neighbours. Because shaded cells never touch, all four orthogonal neighbours of a black cell must be white. The cell you just shaded has four neighbours, and you already have one of them — the sandwich 2 above it. So it proves three new whites: the 2 at row 4 column 3, the 3 at row 4 column 5, and the 3 at row 5 column 4. Dot all three.
Then repeat. That white 3 at row 4, column 5 forces the other 3 in row 4 — the one at column 1 — to be shaded. Row 4, column 1 is black.
Your next move is already waiting. Whitening neighbours also handed you the 3 at row 5, column 4. Row 5 reads 5 1 3 3 2, so that white 3 kills the other 3 in its row: row 5, column 3 is black. Same move, no new thinking.
Check connectivity before every shade. Blacking out row 4 column 1 whitened its neighbours too, including the 5 directly below it at row 5, column 1. Now look at that 5: it is in the bottom-left corner, so it has only two neighbours — row 4 column 1, already black, and row 5 column 2. If you ever shaded row 5 column 2, that corner 5 would be cut off from every other white cell. Note what shading it would not do: it would create no repeated number and it would touch no black cell, so rules 1 and 2 are both perfectly happy. It fails rule 3 and nothing else. So row 5, column 2 must stay white — a cell settled by the shape of the white region rather than by its number.
That is the whole method. You have now found 3 of the 6 black cells and proved six whites — row 3 column 4, row 2 column 5, row 4 columns 3 and 5, row 5 column 4, and row 5 column 2. Check them against the grid on the right, then keep cycling the same moves to finish it.
One more pattern for bigger boards. If the same number appears three times in a row or column, at most one can stay white, so at least two of them are black. When three copies sit consecutively, the middle one must be white — that is just a sandwich again. This little board has no triples; you will meet them on the larger grids.
Why Solvers Like It
Hitori uses no arithmetic and no vocabulary. You are reading position and repetition only, so anyone who can spot two matching numbers can start. And where Sudoku asks you to build up candidate lists, Hitori is the mirror image: it is subtractive. There are no candidate lists to maintain: a dot for white, a fill for black, and that is your whole notation. One move — cross it out or leave it alone. The connectivity rule is what keeps the big grids genuinely demanding.
Play It Online
Hitori plays directly in the browser on our site. Click a cell to shade it, click again to clear it — that is the entire control scheme, because shading is the only move the puzzle has. Black cells that end up touching each other highlight immediately; the other two rules are checked when you press the check button. The general player controls (checking your answer, the timer, working through a set) are covered once in How to Play Puzzles Online.
Playing the sample below is free. Publishing your own playable Hitori puzzles on your own site needs a Creative Interactive or Productivity Interactive edition — see the Hitori product page.
Outcome
Finished a grid with no answer key to hand? Run the three rules as a checklist: no number appears twice in any row or column among the white cells, no two black cells share a side, and you can trace a path of white cells from any white cell to any other. If all three hold, you are done — there is no second solution to worry about.
You now know the goal, the three rules that define a valid Hitori solution, and a deduction chain you can run on any board: spot adjacent pairs, find a sandwich to get a certainty, shade the twins of every white cell, whiten the neighbours of every black cell, and check connectivity before every shade. Want to make your own? See How to Create Hitori Puzzles in Puzzle Maker Pro.
FAQ
What is Hitori?
Hitori is a Japanese number-logic puzzle played on a square grid where every cell already holds a number. You shade cells out until no number repeats in any row or column among the cells left white, no two shaded cells touch edge to edge, and all the white cells remain connected.
How do you solve a Hitori puzzle?
Start by finding a number sandwiched between two copies of the same number — the middle cell must stay white. Then work outward: every white cell forces its same-numbered row and column mates to be shaded, every shaded cell forces its four neighbours white, and no shade may ever cut a white cell off from the rest.
Can two shaded cells touch diagonally?
Yes. Only edge-to-edge contact is forbidden. Diagonal contact is legal, and solved grids commonly contain diagonal runs of shaded cells.
Does every Hitori puzzle have only one solution?
Yes — a well-formed Hitori puzzle has exactly one solution. Every Hitori generated by Puzzle Maker Pro is accepted only when logic alone determines every cell, so a second solution is impossible and guessing is never required.
What happens to the number in a shaded cell?
Nothing — it simply stops counting. It is removed from its row and column for the purposes of the no-repeats rule. On the printed solution the shaded cells are filled solid and their numbers are hidden.
What numbers are used in a Hitori puzzle?
A Hitori grid uses the numbers 1 up to the grid’s side length, so a 5 × 5 grid uses 1 to 5 and an 8 × 8 grid uses 1 to 8. Repeats within that range are what create the puzzle.
Do you ever have to guess in Hitori?
No. A properly built Hitori is always solvable by pure deduction. Every difficulty setting is held to the same standard, so an Expert puzzle is exactly as logical as an Easy one — it is not a harder puzzle because it is less fair.