X-Wing - The Entry-Level Fish Pattern

Q: What is X-Wing in sudoku?

X-Wing is a fish pattern where a digit appears in exactly two cells in each of two rows, aligned in the same two columns. That lets you remove the digit from the rest of those columns.

Q: How do I find an X-Wing?

Count candidate positions digit by digit. When one number appears exactly twice in two separate rows and those candidate positions line up in the same columns, you have an X-Wing.

Q: What is Swordfish vs X-Wing?

Swordfish is the three-row or three-column extension of the same fish logic. X-Wing uses two rows and two columns, while Swordfish scales the idea to three.

X-Wing is often the first advanced fish pattern players learn in sudoku. It appears when one digit occurs in exactly two candidate positions in one row and exactly two candidate positions in another row, and those positions line up in the same two columns. Because the digit must occupy one of those two cells in each row, you can eliminate it from every other cell in the matching columns.

This sounds abstract at first, but it becomes manageable once you count candidates digit by digit. X-Wing is a major step up from pairs and singles, and it appears regularly in Hard Sudoku and Expert Sudoku.

How X-Wing Works

Imagine candidate 6 appears only in c2 and c8 of row 3, and only in c2 and c8 of row 7. Those four cells make the corners of a rectangle. Since row 3 must place one 6 in c2 or c8 and row 7 must do the same, no other cell in column 2 or column 8 can contain 6.

The same reasoning works the other way round if you start from columns instead of rows.

Row-Based vs Column-Based X-Wings

Some X-Wings are easier to see by scanning rows, others by scanning columns. Strong solvers check both. A practical habit is to choose one digit and count how many candidates it has in every row. Rows with exactly two candidates are the best starting point.

Why X-Wing Matters

X-Wing teaches you to stop thinking cell by cell and start thinking in structures across the whole grid. That mindset prepares you for Y-Wing and Swordfish, where global candidate patterns matter even more.

Frequently Asked Questions

What is X-Wing in sudoku?

It is a fish pattern built from two rows and two columns for a single digit.

How do I find an X-Wing?

Count candidate positions for one digit and look for two rows or columns with matching pairs.

What is Swordfish vs X-Wing?

Swordfish is the larger three-row or three-column version of the same idea.

Next Steps

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Hub Sudoku Techniques Go back to the full technique map and choose another solving pattern to study.Prerequisite Pointing Pairs Sudoku Review the earlier pattern first if this technique still feels too abstract or unstable.Next Technique Y Once this pattern feels natural, continue to the next technique in the solving ladder.

Practice This Technique

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