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XY-Wing Sudoku: How This Intermediate Technique Eliminates Candidates

By Michel ·

You have worked through naked singles, hidden singles, pointing pairs, and basic pair techniques. The grid is still stuck. This is exactly when XY-Wing tends to appear. It is the first technique that feels genuinely clever — a three-cell chain that forces an elimination across the board through pure logic. The pattern is useful when its exact conditions occur; a difficulty label does not guarantee that a puzzle contains one.

What Is the XY-Wing Technique?

XY-Wing uses three cells: one pivot and two pincers. Here is the structure:

  • Pivot: a cell with exactly two candidates, which we call X and Y.
  • Pincer 1: a cell that sees the pivot and contains exactly the two candidates X and Z.
  • Pincer 2: a cell that sees the pivot and contains exactly the two candidates Y and Z.

The pivot must be either X or Y:

  • If the pivot is X → Pincer 1 must be Z (because X is taken by the pivot).
  • If the pivot is Y → Pincer 2 must be Z (because Y is taken by the pivot).

In either case, at least one pincer must be Z. Therefore, any cell that sees both pincers cannot be Z and can have Z eliminated from its candidates.

Two cells "see" each other if they share the same row, column, or 3×3 box. A cell visible to both pincers simultaneously is in the elimination zone.

How XY-Wing Works — The Pivot and Pincers

Concrete example: The pivot at R4C5 has candidates {3, 7}. Pincer 1 at R4C9 has {3, 5}. Pincer 2 at R1C5 has {7, 5}. Here X=3, Y=7, Z=5.

  • Both pincers can see the pivot (they share the same row or column as the pivot).
  • Any cell that can see both pincers — meaning it shares a row, column or box with each of R4C9 and R1C5 — can have 5 eliminated.

In this case R1C9 sees both pincers (it is in row 1 with Pincer 2, and in column 9 with Pincer 1). Remove 5 from R1C9. That one elimination may be enough to unlock the rest of the grid.

Step-by-Step: How to Find XY-Wings

  1. Find all bi-value cells — cells with exactly two candidates. List them. These are your potential pivots and pincers.
  2. Pick a pivot. Take any bi-value cell with candidates {X, Y}.
  3. Find Pincer 1: look for a bi-value cell that the pivot can see, containing X and some third digit Z.
  4. Find Pincer 2: look for a bi-value cell that the pivot can see, containing Y and the same Z.
  5. Identify the elimination zone: cells that can see both pincers simultaneously.
  6. Eliminate Z from any cell in the elimination zone that currently has Z as a candidate.

XY-Wing vs Y-Wing: Are They the Same?

Yes. Y-Wing is an older name for exactly the same technique. Modern Sudoku notation uses XY-Wing to be more precise about the candidate labels involved (X, Y, and Z). If you see both names in solving guides, they refer to the identical three-cell elimination pattern.

XY-Wing vs XYZ-Wing: The Key Difference

In an XY-Wing, the pivot has exactly two candidates. Each pincer must see the pivot; the elimination rule depends on seeing both pincers, not on a blanket restriction against shared boxes. In an XYZ-Wing, the pivot has three candidates — X, Y, and Z — and the elimination zone shrinks. With XYZ-Wing, only cells that can see all three cells (pivot, Pincer 1, and Pincer 2) have Z eliminated. Check the visibility condition separately for each proposed target.

When to Use XY-Wing

XY-Wing appears on hard and expert puzzles, typically after you have exhausted:

When none of those produce a move and you have multiple bi-value cells, scan for XY-Wing. It marks the transition from intermediate to genuinely advanced solving.

Want to practise the exact pattern? Work through the interactive XY-Wing example, then choose a difficulty in today's player. A daily puzzle is not guaranteed to contain an XY-Wing.

Frequently Asked Questions

What is the XY-Wing technique in Sudoku?

XY-Wing is a three-cell elimination technique. A pivot cell has two candidates (X and Y). Two pincers each share one candidate with the pivot (X+Z and Y+Z). Because the pivot must be X or Y, at least one pincer must be Z. Any cell that sees both pincers cannot be Z.

What is the difference between XY-Wing and Y-Wing?

They are the same technique. Y-Wing is the older name; XY-Wing is the modern label. Both describe the same pivot-and-pincers elimination pattern.

What is the difference between XY-Wing and XYZ-Wing?

In XY-Wing, the pivot has two candidates. In XYZ-Wing, the pivot has three candidates (X, Y, Z). The XYZ-Wing elimination zone is narrower — only cells that see all three cells have Z eliminated, not just cells that see both pincers.

When should I use XY-Wing?

Use XY-Wing on hard and expert puzzles after exhausting singles, locked candidates, and basic pairs and triples. It is one of the first non-linear techniques and indicates you are moving into advanced solving territory.