W-Wing

Two matching pairs linked by a strong link remove a digit.

Learn the W-Wing Sudoku technique: two bivalue cells {x,y} joined by a strong link on x let you remove y from cells that see both.

How to use it

1. Find two matching pairs. Find two cells with the same two candidates, x and y, that do not see each other.
2. Find the strong link. Find a row, column, or box where x appears in just two cells — one seeing the first pair, the other seeing the second.
3. Eliminate y. One of the two pairs must be y, so remove y from every cell that sees both of them.