--- title: "W-Wing: Sudoku Technique #23 | Sudoku Flow" description: "W-Wing: Two matching bivalue cells share two candidates. A strong link on one of the two candidates, with each end seeing a different one of the cells, forces…" url: https://sudokuflow.com/lessons/wWing/ language: en --- [Sudoku technique lessons](https://sudokuflow.com/lessons/) / W-Wing Lesson 23 # W-Wing ## The rule Two matching bivalue cells share two candidates. A strong link on one of the two candidates, with each end seeing a different one of the cells, forces at least one matching cell to hold the other candidate, so any cell that sees both loses it. ## Step by step 1. The two cells marked hold only 3 and 7. In this row, 7 can go only in the two cells marked (a strong link), and each of them sees a different cell. Whichever of them holds 7, the cell it sees cannot, so that cell must be 3. This is a W-Wing! 2. At least one of the two matching bivalue cells must be 3, so we can remove the candidate 3 from any other cell that sees both matching cells. [Read the full lesson, with more examples →](https://sudoku.rubigogames.com/techniques/w-wing.html) In our app, when this technique is the next step, the hint names it and shows you why, step by step. No ads, free to download. [App Store iPhone, iPad, Mac](https://apps.apple.com/app/apple-store/id6502922368?pt=125379530&ct=sudokuflow_cta&mt=8) [Google Play Android](https://play.google.com/store/apps/details?id=com.rubigogames.sudoku&referrer=utm_source%3Dsudokuflow%26utm_medium%3Dcta%26utm_campaign%3Dlesson) ## Try it on more boards Each board is a real puzzle from our app, at a moment where W-Wing applies. Find the step yourself, or tap Hint and the app's own hint walks you through it. W-Wing practice board: ```text . 9 . | . 3 2* | . . . . . 5 | . 6* 7 | . 9 2 . 6 . | . . 9 | 8 . . ---------+----------+--------- 9 . . | 3 8 . | 2* 7 . 8 2 . | . . 1 | . . . . 7* . | 9 2* . | . 4 8* ---------+----------+--------- . . . | 6 . . | . 2* . . 1 . | . 9 8* | . 5 . 7 . . | 2 . 3 | 6 8* . ``` Digits marked * were filled in by a player; the others were printed with the puzzle. ![Sudoku app icon](https://sudokuflow.com/assets/app-icon.png) ## Want more boards like this? We also make a Sudoku app for iPhone, iPad, Mac and Android. There are no ads in it at all, it works offline, and when you ask for a hint it shows you the technique instead of just filling in a number. [App Store iPhone, iPad, Mac](https://apps.apple.com/app/apple-store/id6502922368?pt=125379530&ct=sudokuflow_web&mt=8) [Google Play Android](https://play.google.com/store/apps/details?id=com.rubigogames.sudoku&referrer=utm_source%3Dsudokuflow%26utm_medium%3Dweb%26utm_campaign%3Dsite) Sudoku Flow is made by Rubigo Games, the developer of the Sudoku app recommended on this site.