How to Find & Solve the X-Wing Pattern in Sudoku
The X-Wing is the most famous fish technique in Sudoku. It exploits 2 parallel rows sharing candidates in 2 columns to make surgical candidate eliminations across entire vertical lines.
Hands-On X-Wing Elimination
Examine Rows 2 and 8. In both rows, candidate 7 appears in only two cells (Columns 2 and 8), forming a rectangle. Execute the elimination to prune candidate 7 from other cells in these columns (R5C2 and R5C8)!
The 3-Step X-Wing Formula
- Find Two Parallel Base Rows: Look for a specific digit (e.g. 7) that only appears twice in Row A, and twice in Row B.
- Check Column Alignment: Verify that the two cells in Row A align in the exact same columns as the two cells in Row B.
- Eliminate Along the Columns: Delete that candidate number from all other cells in those two columns.
Frequently Asked Questions
What is an X-Wing in Sudoku? ▼
An X-Wing is an advanced solving technique where a specific candidate digit appears exactly twice in two different rows, and those candidate cells align in the exact same two columns (forming the 4 corners of a rectangle). Because the digit must occupy opposite diagonal corners, it cannot appear in any other cell of those two columns.
Can an X-Wing be formed by columns instead of rows? ▼
Yes! A column-based X-Wing occurs when a digit appears in only two cells across two columns, sharing the same two rows. In that case, the digit is eliminated from all other cells in those two rows.
Why is it called an X-Wing? ▼
The name comes from the diagonal cross-pattern formed between the four corner cells: if corner A is true, corner D is true; if corner B is true, corner C is true. The lines connecting the valid combinations form an 'X', reminiscent of Star Wars X-Wing starfighters.
Put the X-Wing Pattern into Practice
X-Wing patterns appear frequently in advanced boards. Practice your fish deduction skills on our Expert Sudoku or Evil Sudoku boards, or advance to the 3-line extension: Swordfish.