The XY-Wing uses three bi-value cells - a pivot and two wings - to eliminate a candidate from any cell that sees both wings.
An XY-Wing requires three cells, each containing exactly two candidates (bi-value cells). The central cell, called the "pivot," has candidates X and Y. It connects to two "wing" cells: one with candidates X and Z (sharing X with the pivot), and another with candidates Y and Z (sharing Y with the pivot). Each wing must share a unit (row, column, or box) with the pivot, but the two wings do not need to share a unit with each other.
The elimination logic is elegant: if the pivot cell contains X, then the XZ wing cannot be X, so it must be Z. If the pivot cell contains Y, then the YZ wing cannot be Y, so it must be Z. In either case, at least one wing cell must contain Z. Therefore, any cell that can "see" both wing cells (shares a unit with both) cannot contain Z - it would create a contradiction no matter what the pivot holds.
This technique introduces chain-based reasoning, which is a stepping stone toward more complex strategies like Forcing Chains. Understanding XY-Wings deepens your ability to think about implications and logical dependencies in Sudoku. For related terminology, see our Sudoku glossary.
XY-Wings become relevant when pattern-based techniques like X-Wing and Swordfish are not producing results. They are particularly useful in hard and expert Sudoku puzzles where the grid has many bi-value cells after initial eliminations.
The XY-Wing is one of the most satisfying techniques to apply because the logic is clean and the eliminations can be dramatic. If you enjoy logical deduction, this technique and its extensions will appeal to you. For the full progression of techniques, visit our strategy guide or review how to play Sudoku.
The XY-Wing is classified as an advanced-level technique. It requires understanding bi-value cells, chain reasoning, and visibility between cells - skills that distinguish advanced solvers from intermediate ones.
Never needed - basic singles handle these puzzles
Not needed - intermediate techniques are sufficient
Occasionally needed when fish patterns are absent
Frequently useful - a key technique at expert level
An XY-Wing (also called Y-Wing) is an advanced technique involving three cells, each containing exactly two candidates. A central "pivot" cell with candidates XY connects to two "wing" cells: one with candidates XZ and another with candidates YZ. Any cell that can see both wing cells can have candidate Z eliminated.
The pivot cell must share a unit (row, column, or box) with each wing cell, but the two wing cells do not need to share a unit with each other. The pivot has candidates XY, one wing has XZ, and the other wing has YZ. The shared candidate Z between the two wings is the one that gets eliminated from cells that see both wings.
Consider the pivot cell with candidates XY. If the pivot is X, then the wing with XZ must be Z. If the pivot is Y, then the wing with YZ must be Z. Either way, at least one wing cell must contain Z. Therefore, any cell that sees both wing cells cannot contain Z.
Despite similar names, they are completely different techniques. X-Wing is a "fish" pattern based on row-column alignments of a single candidate. XY-Wing is a chain-based technique involving three bi-value cells with different candidate pairs. The elimination logic is fundamentally different.
Yes, XY-Wing and Y-Wing refer to the same technique. The names are used interchangeably in the Sudoku community. Some sources prefer "Y-Wing" because of the Y-shaped connection pattern between the three cells.
Find a 'pivot' cell with exactly two candidates. Here R5C5 has [1, 2].
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