How to play Hitori

The rules

Cross out squares until three things are true. No number appears twice among the squares still showing in any row or column. No two crossed-out squares touch edge to edge. And everything still showing forms one connected group, so no part of the board is cut off from the rest. You write nothing — every number is already there and the whole game is deciding what to remove. That last rule is the one that makes it: the other two can be checked a square at a time, but staying joined up is a fact about the whole board, and the closing moves usually come from noticing that crossing one more out would strand a corner.

Play today's Hitori →

What is a Hitori?

Hitori is a logic puzzle in which you cross out numbers from a filled grid until no number repeats among the squares still showing in any row or column, no two crossed-out squares touch edge to edge, and every square still showing is connected to all the others.

How do you solve a Hitori?

  1. 01

    Find a number sandwiched between two of itself

    Look along each line for the same number either side of a different one. The two matching squares cannot both stay, so one is crossed out, and since crossed squares may not touch, the middle square can never be crossed. Mark it as staying.

  2. 02

    Use a pair of matching neighbours

    Two of the same number side by side cannot both be crossed, because crossed squares may not touch, and cannot both stay, because the line would repeat. Exactly one survives, so every other copy of that number in the line is crossed out.

  3. 03

    Let each decision spread

    Whenever you cross a square out, its four edge neighbours must stay. Whenever a square is confirmed as staying, every other copy of its number in its row and column must go. Alternate the two until the board stops changing.

  4. 04

    Leave the unrepeated numbers alone

    A number that appears once in its row and once in its column is never forced out, and no rule ever requires a square to be crossed. Every puzzle here has exactly one solution, so such a square stays, and marking it often closes a nearby decision.

  5. 05

    Watch the corners for cut-offs

    A corner square has only two neighbours; if both were crossed it would be stranded, so at least one stays, which often decides a pair. The same applies to any edge square with a crossed square on one side: the square on its other side must stay.

  6. 06

    Check that the board still hangs together

    The connection rule is about the whole board, so the site judges it only on the finished answer. Before crossing a late square, trace whether a chain of crossed squares touching at their corners would run from edge to edge and split the board. If it would, that square stays, and the last few squares usually fall to exactly this check.

Common Hitori mistakes

  • Crossing out two squares that share an edge. The board marks it, but the reasoning that led there is usually wrong further back.
  • Crossing out a number that appears only once in its line. Nothing ever forces that, and on a board with a single solution it is always wrong.
  • Forgetting connectivity until the end. Crossed squares touching at their corners can wall off the board without ever touching edge to edge, and by then several decisions have to be undone.
  • Treating a temporarily disconnected board as an error. Stranded regions are normal part-way through and the board only judges connection when you submit; use it to constrain what you cross next, not as an alarm.

Where does Hitori come from?

Hitori was created by the Japanese puzzle publisher Nikoli and first appeared in its magazine in the early 1990s. The name is short for a Japanese phrase meaning “leave me alone”, a nod to each number being left standing alone in its row and column once its duplicates are gone.

It spread abroad in the mid-2000s with the other Nikoli puzzles that followed Sudoku, and unlike most of them it never acquired a second name.

Can two crossed-out squares touch at a corner in Hitori?

Yes. The rule forbids crossed squares sharing an edge, and corners do not count; diagonal chains of crossed squares are the usual way a board gets split in two, so watch them rather than avoid them.

How long does an 8×8 Hitori take?

The sandwich and pair patterns settle most of an eight-by-eight in a few minutes, and the connection endgame adds a few more. There is one Hitori here a day, new at midnight UTC, free with no sign-up, and it plays on a phone by tapping squares.

Does Hitori ever need guessing?

Not on this site. Every daily board is checked to have exactly one solution before it is published, so when you are stuck there is a deduction available, most often from the connection rule.