The X-Wing identifies a candidate pattern across two rows and two columns, enabling eliminations from intersecting cells.
An X-Wing occurs when a particular candidate appears in exactly two cells in each of two different rows, and those four cells are aligned in the same two columns. This creates a rectangular pattern where the candidate must occupy two of the four cells in a diagonal arrangement - forming an X shape.
Because the candidate must appear once in each of the two rows (in one of the two aligned columns), and once in each of the two columns, any other occurrences of that candidate in those two columns can be eliminated. For the complete strategy with worked examples, see our X-Wing strategy guide.
To find an X-Wing, scan each candidate digit across the grid. Look for rows where that candidate appears in exactly two cells. If you find two such rows where the candidate falls in the same two columns, you have found an X-Wing. The pattern also works in reverse: look for columns with exactly two cells containing the candidate, aligned in the same two rows.
The elimination logic of X-Wing is based on the fact that the candidate must appear exactly once in each of the two defining rows. Since it can only go in one of two columns in each row, and both rows use the same two columns, the candidate is "locked" into those four cells. It must occupy exactly two of them - one in each row, one in each column.
This means no other cell in those two columns can contain the candidate. All other instances of that candidate in the two columns are eliminated. This can trigger further deductions and often helps break through difficult sections of a puzzle where simpler techniques have stalled.
X-Wing belongs to a family of patterns called "fish" techniques. The same logic extends to larger groups: Swordfish uses three rows and three columns, and Jellyfish uses four rows and four columns. Each follows the same principle - when a candidate is confined to N columns across N rows, it can be eliminated from other cells in those columns.
While Swordfish and Jellyfish are harder to spot, understanding X-Wing makes learning them much easier since the underlying logic is identical. Mastering X-Wing is the gateway to the entire fish family of techniques.
Explore more Sudoku concepts in the complete glossary.
An X-Wing is an advanced elimination technique that occurs when a specific candidate appears in exactly two cells in each of two different rows, and those cells line up in the same two columns. The candidate can then be eliminated from all other cells in those two columns.
The name comes from the shape formed by connecting the four cells involved in the pattern. When you draw lines between the cells diagonally, they form an X shape. The name also references the X-Wing starfighter from Star Wars, which was popular in the Sudoku community when the technique was named.
X-Wing is considered an advanced technique, but the concept itself is straightforward once you understand candidate tracking. The challenge is spotting the pattern in a busy grid. Practice with puzzles that specifically require X-Wing to build your pattern recognition skills.
X-Wing, Swordfish, and Jellyfish are all members of the same family of techniques called 'fish' patterns. X-Wing uses 2 rows and 2 columns, Swordfish uses 3 rows and 3 columns, and Jellyfish uses 4 rows and 4 columns. The elimination principle is the same for all three.
We're tracking where the digit 5 can go. Each marked cell shows 5 as a possible candidate.
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