You've mastered naked pairs, hidden pairs, the X-Wing… but level 7 grids still block you? The Y-Wing is very likely the technique you're missing.
The Y-Wing (also called XY-Wing) belongs to the family of advanced techniques, alongside the W-Wing, XY-Chain and X-Cycles. Simple to understand once the mechanism clicks, it is absolutely essential to progress toward hard grids.
The Y-Wing principle (pivot + two wings), how to identify the cells involved, and the Domino33 method to find it efficiently in any grid. The full 20-minute video provides all the practical examples you need.
🎬 Full Domino33 video on Y-Wing
Before the written content, here is the full 20-minute video: theory illustrated with many examples in part 1, then the search method in part 2 — the most important part — and a concluding quiz:
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The article below follows the same structure as the video so you can learn in whichever format you prefer.
Part 1
What is a Y-Wing?
The three players: pivot and two wings
A Y-Wing always involves exactly 3 cells, split into two distinct roles:
- The pivot: a cell containing exactly 2 candidates, which we call A and B
- Wing 1: a cell that sees the pivot, with candidates A and C
- Wing 2: a cell that sees the pivot, with candidates B and C
Notice that both wings share the candidate C. That shared candidate is what can be eliminated.
The elimination logic
Reason as follows: whatever value the pivot takes, one of the two wings will always contain C. If the pivot takes value A, then wing 1 takes value C. If the pivot takes value B, then wing 2 takes value C. C will always be present in at least one of the two wings.
The consequence: any cell that sees both wings simultaneously cannot contain C and it can be eliminated from its candidates.
The X-Wing uses 4 aligned cells forming a rectangle. The Y-Wing uses only 3 cells that do not need to be aligned, making it more flexible and more frequent in hard grids.
Diagram
Here is a simplified diagram to visualise the mechanism. The pivot has candidates {4,7}, wing 1 has {4,9}, wing 2 has {7,9}. Candidate 9 can be eliminated from any cell that sees both wings:
| {7,9} Wing 2 | ✗ 9 | |||||||
| {4,7} Pivot | {4,9} Wing 1 | |||||||
The ✗ cell sees both wings: candidate 9 (C) can be eliminated.
The video develops this diagram across many examples from real grids, with different configurations of pivot and wings. Seeing multiple real cases is what builds the reflex.
Part 2
The search method — the key to success
Knowing the theory is not enough: you also need to find Y-Wings quickly in a grid. That is what this part covers, and it is the most important section of the video.
Step 1 — Find bivalue cells
A bivalue cell is a cell that contains only 2 candidates. These are the ideal candidates for the pivot role. Always start by identifying them in the grid — they are your entry point.
Step 2 — Analyse the neighbours of each bivalue cell
For each bivalue cell found (candidates A and B), look at all the cells it sees (same row, column or box). Among them, look for bivalue cells containing A + another candidate C, or B + another candidate C.
Step 3 — Verify the shared candidate C
If you find two neighbours of the pivot containing {A,C} and {B,C} respectively, with the same C in both: you have found a Y-Wing. All that remains is to identify the cells that see both wings simultaneously and eliminate C from them.
Many players scan the whole grid visually looking for a Y-Wing. This is inefficient. The right approach: start systematically from bivalue cells. This disciplined search method also applies to many other advanced techniques.
🎬 See the method in action
In the video, I walk through the method step by step on several real grids. The final quiz lets you check your understanding before applying it on your own.
Part 3
Application quiz
You have covered the theory and the method. Test your knowledge with this 4-question quiz. Good luck!
❓ Frequently asked questions
A Y-Wing involves exactly 3 cells: a pivot and two wings. This distinguishes it from the X-Wing, which uses 4 cells aligned in a rectangle.
The X-Wing uses 4 cells aligned on 2 rows and 2 columns. The Y-Wing uses 3 cells (pivot + 2 wings) that do not need to be aligned. Both are candidate elimination techniques, but the Y-Wing is more flexible and appears more often in level 7+ grids.
The Y-Wing typically appears in level 7 and above grids. It belongs to the advanced techniques family, alongside W-Wing, XY-Chain and X-Cycles. Mastering the Y-Wing is a necessary step to solve hard grids independently.
After the Y-Wing, the natural next steps are the W-Wing, then the XY-Chain (a generalisation of the Y-Wing over a chain of bivalue cells). These techniques, along with XYZ-Wing and Sashimi X-Wing, are all covered in the book Sudoku — 6 Advanced Techniques · 100 Exercises.
📋 Summary
The Y-Wing essentials
- Configuration: 1 pivot {A,B} + 1 wing {A,C} + 1 wing {B,C}
- Requirement: the pivot must see both wings; wings share a common candidate C
- Action: eliminate C from any cell that sees both wings simultaneously
- Starting point: find bivalue cells (2 candidates)
- Appears in: level 7+ grids (hard to expert)
- Next technique: W-Wing, XYZ-Wing, XY-Chain
As with any technique, regular practice is what builds the reflex. The Domino33 video walks through many real grid examples — the most effective way to make Y-Wing recognition automatic.
📘 Go further with Domino33
The Y-Wing is one of 6 advanced techniques covered in the book Sudoku — 6 Advanced Techniques. 100 progressive exercises to master X-Wing, Y-Wing, W-Wing, XYZ-Wing, Sashimi X-Wing and SwordFish.