XY-Wing Explained Simply: Three Two-Candidate Cells

An XY-Wing uses a pivot cell with candidates XY and two wings, XZ and YZ. The wings each see the pivot, while the wings also share a peer that can see both.

The conclusion is a candidate elimination, not a placement.

Find the pivot

Look for a two-candidate cell XY. It must see two other two-candidate cells, one containing XZ and the other YZ. Keep the labels abstract until the visibility is confirmed.

Confirm both wings

Each wing shares one candidate with the pivot and one candidate Z with the other wing. The pivot and each wing must be peers; the wings do not need to share a unit with each other.

Follow the implication

If the pivot is X, the YZ wing cannot use Y and must use Z. If the pivot is Y, the XZ wing cannot use X and must use Z. Either way, one wing is Z.

Find a common peer

Any cell that sees both wings cannot contain Z, because one of the wings must take it. Remove Z only from those common peers.

Check the exact shape

Three bivalue cells alone do not make an XY-Wing. Recheck the candidate labels and visibility before eliminating, then rescan for the simple result it creates.