Choose a digit and find rows where it has exactly two candidate cells.
X-Wing
Your first advanced pattern — a rectangle that eliminates across the grid.
The X-Wing works on a single digit. Find two rows in which that digit has only two possible cells, and those cells line up in the same two columns. The four cells form a rectangle. The digit must occupy opposite corners, which means it can be eliminated from those two columns everywhere else.
Worked example
6
6
6
6
How to apply it
Look for two such rows whose candidate cells fall in the same pair of columns.
Those four cells are your X-Wing rectangle.
Eliminate the digit from every other cell in those two columns.
The same pattern works with rows and columns swapped.
When to use it
The X-Wing is the first technique that feels genuinely advanced, and the foundation for Swordfish and Jellyfish. Reach for it on expert and evil grids when locked candidates and pairs have run out.
Frequently asked questions
When should I look for an X-Wing?
Only after singles, pairs and locked candidates stall — usually on expert and evil puzzles. Scan one digit at a time for the rectangle pattern.