The X-Wing
Master the X-Wing: when a digit sits in exactly two cells of two rows that share the same two columns, eliminate it from the rest of those columns.
The X-Wing is the first "fish" pattern and a rite of passage for advanced solvers. Find a digit that appears in exactly two cells of two different rows, and where those cells line up in the same two columns.
Those four cells form a rectangle. Whichever way the digit falls, it occupies opposite corners — so it cannot appear anywhere else in those two columns, and you can eliminate it there. (The same works swapping rows and columns.)
X-Wings crack many expert boards that singles and pairs cannot. The example highlights the four-corner pattern and the candidates it removes.
Practise the X-Wing
The best way to learn a technique is to use it. Play a puzzle at the level where it first appears, or drop a tricky board into the solver to watch it in action.
Frequently asked questions
What is an X-Wing in Sudoku?
A pattern where a digit is restricted to two cells in each of two rows, and those cells share two columns. The digit can then be removed from the rest of those columns (or rows).
Is the X-Wing hard to learn?
It takes practice to spot, but the logic is simple: a rectangle of one digit forces it onto opposite corners, freeing the rest of the lines.
More guides on the Learn hub.