XY-Wing

Difficulty level: expert

An XY-Wing uses three cells that each hold exactly two candidates: a pivot with candidates XY, and two pincers sharing a unit with the pivot, holding XZ and YZ.

Whichever value the pivot takes, one of the pincers is forced to Z. Z is therefore certain to occupy one pincer or the other — so any cell that sees both pincers can never be Z.

XY-Wings reward disciplined pencil marks: the pattern only emerges when bivalue cells are accurately tracked. It is often the key that cracks otherwise stuck expert grids.

Worked example

Pivot (top-left, candidates 1-2) sees both pincers (1-3 and 2-3). Either way the pivot resolves, a pincer becomes 3 — cells seeing both pincers can never be 3.
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How to apply it

  1. Mark all bivalue cells (exactly two candidates).
  2. Find a pivot XY with two peers holding XZ and YZ.
  3. Identify cells that share a unit with both pincers.
  4. Erase Z from those cells.

Practice it

The fastest way to internalize the xy-wing is to use it. Play a free expert puzzle — the in-game hint system points out exactly this pattern when it appears, or browse the full technique library.