Sudoku technique guide

XY-Wing Sudoku Technique

An XY-Wing uses a pivot and two wing cells to remove a shared candidate. This guide explains the idea in plain English, when to look for it, and the common mistake to avoid.

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At a glance

Difficulty

Hard

This is where XY-Wing normally sits in a human solving path.

Family

Wing techniques

It belongs to the wing techniques group of Sudoku logic.

Main action

Usually remove candidates

Most technique moves reduce notes first. That often reveals a simpler placement afterwards.

What is XY-Wing?

An XY-Wing uses a pivot and two wing cells to remove a shared candidate.

The important thing is that this is logic, not guessing. You are using the current candidates to prove that a number must either go in one place, or cannot stay in another place.

In SudoSketch, this technique is designed to work with notes and Coach highlighting, so the key cells and removal cells can be shown clearly.

How XY-Wing works

Find a two-candidate pivot cell.
Find two wing cells that see the pivot and share one candidate each with it.
The wings share a removal candidate. Any cell that sees both wings can lose that candidate.

When to look for it

Look for XY-Wing after easier moves have stopped working. First check for naked singles, hidden singles, locked candidates and simple pairs. If those do not move the puzzle forward, this technique may be worth checking.

For learning, do not try to scan for every advanced technique at once. Pick one method, understand the shape, and practise spotting that one pattern.

Common mistake

The pivot and wings must be two-candidate cells. Extra candidates break the pattern.

If you are unsure, rebuild the candidates first. Bad notes create bad logic, and Sudoku will absolutely punish you for it like a tiny spreadsheet goblin.

XY-Wing FAQ

What is XY-Wing in Sudoku?