Difficulty
Medium
Sudoku technique guide
XY-Wing
Sometimes the obvious moves disappear, but the grid is still giving you a useful clue. XY-Wing is a calm way to follow it.
By the end, you will know what to notice, how the idea works and when it is worth using.
At a glance
Technique family
Wings
Purpose
Removes candidates
Typical puzzle stage
Middle
Frequency
Occasional
Prerequisites
Bivalue cells and candidate marks
Why this technique matters
XY-Wing teaches you to compare three linked cells instead of one unit at a time. It is a compact, useful pattern when the grid has many bivalue cells.
The idea in plain English
An XY-Wing has a pivot with candidates X and Y, plus two pincers it sees: one with X and Z, and one with Y and Z. Any cell that sees both pincers cannot contain Z.
How to recognise it
The key picture is two pincers sharing one candidate Z, while each shares a different pivot candidate.
Pause when you see this shape. You do not have to force it; just check whether the pattern is complete.
How the logic unfolds
Think of this as a short conversation with the grid. Take one check at a time, and let each answer tell you what to inspect next.
Start by. Find a bivalue pivot {X,Y}.
Then. Find one visible bivalue cell {X,Z} and another visible bivalue cell {Y,Z}.
Next. Confirm both pincers see the pivot.
Finally. Remove Z from cells that can see both pincers.
When it usually appears
Look for it after pairs and locked candidates, when several bivalue cells cluster around a pivot.
Common traps
These are easy places to get turned around. They are useful checks, not signs that you are doing badly.
- Eliminating Z from cells that see only one pincer. A target must see both.
- Mixing up the pivot candidates and the shared pincer candidate.
Frequently asked questions
Do the pincers have to see each other?
No. Both need to see the pivot; the target sees both pincers.
Does XY-Wing place a digit?
Usually it removes a candidate and may reveal a later placement.
Quick takeaway
- A XY-Wing belongs to the wings family.
- Its purpose is to remove candidates.
- Look for a complete pattern, not one that only nearly fits.
- It is most useful middle.
- Once you make the deduction, return to the simpler scans.