X-Wing in Sudoku: How to Spot It
Learn the X-Wing Sudoku technique with a simple candidate pattern, clear elimination rule, and practice-focused explanation.
Guided example
See the X-Wing on this board
Read this as one teaching unit: first identify the active unit, then the marked pattern cells, then the candidates removed or maintained.
Quick answer
An X-Wing in Sudoku is a rectangle pattern for one candidate. If that candidate appears in the same two columns in two different rows, it must occupy opposite corners of the rectangle, so that candidate can be removed from other cells in those columns.
How to spot it
Follow the board in order
- 1 Choose one candidate number and ignore the other candidates for a moment.
- 2 Find two rows where that number appears in exactly the same two columns, or two columns where it appears in exactly the same two rows.
- 3 Confirm the four candidate positions form a rectangle.
- 4 Remove that candidate from other cells in the affected columns or rows.
What is an X-Wing?
An X-Wing is a rectangle formed by one candidate appearing in exactly two positions in each of two rows, and those positions line up in the same columns. The same logic also works with rows and columns reversed.
When to look for it
Look for X-Wings after simpler candidate eliminations are no longer moving the puzzle forward. Choose one number and scan rows or columns for matching two-position patterns.
Example walkthrough
This walkthrough uses a real hard app puzzle tagged X-Wing. Candidate 7 is confined to two columns across two rows: the four blue corner cells. That rectangle means the controlled columns must get their 7s from the rectangle, so the green cell r3c1 cannot keep candidate 7.
Why the elimination works
If row 4’s 7 and row 7’s 7 are locked into columns 4 and 6, then those columns will receive their 7s from the rectangle. No other cell in columns 4 or 6 can be 7.
X-Wing vs. Naked Pair
A Naked Pair works inside one row, column, or box using two cells with the same two candidates.
An X-Wing works across two rows and two columns using one candidate in four aligned positions.
Common mistake
Do not look for any rectangle of candidates. An X-Wing needs one candidate to appear in exactly the same two positions across two rows or across two columns.
FAQ
What is an X-Wing in Sudoku?
An X-Wing is a rectangle pattern where one candidate appears in two matching positions across two rows or two columns.
How do you spot an X-Wing?
Pick one candidate and find two rows with that candidate in the same two columns, or two columns with that candidate in the same two rows.
What can you eliminate with X-Wing?
You eliminate that candidate from the other cells in the affected columns or rows outside the rectangle.
Is X-Wing an advanced Sudoku technique?
Yes. X-Wing is usually considered advanced because it requires scanning candidate positions across multiple rows or columns.
In this lesson
- Board example: see the pattern first.
- Walkthrough: connect each highlight to the rule.
- FAQ: check edge cases after the move is clear.
Practice this technique in Sudoku Coach
Read the pattern, then practice it step by step with guided hints that explain why the move works.
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Hidden Pair in Sudoku: How to Spot It
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