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X-Wing Technique: 2x2 Rectangle Elimination Explained

Master the famous X-Wing technique in Sudoku with clear 9x9 diagrams. Learn how a 2x2 candidate rectangle across two rows or columns eliminates candidates.

When basic single-unit techniques (Naked Singles, Hidden Singles, Locked Candidates, and Pairs) can no longer advance the grid, the X-Wing technique is your primary gateway into advanced Sudoku solving. By spotting a 2×2 rectangle formed by a single candidate digit across two parallel rows (or columns), you can eliminate that digit from the rest of the intersecting columns (or rows).

1. Conditions for a Row-Based X-Wing

Focus on a single digit (e.g., 7).
Find two separate rows where digit 7 can only go into exactly two cells each.
Those four candidate cells align in the exact same two columns, forming the four corners of a rectangle.

2. 9×9 Visual Diagram of an X-Wing

In the diagram below, Row 2 and Row 7 each have only two possible spots for digit 7: Column 2 and Column 8 (green cells).

.	7✕	.	.	.	.	.	7✕	.
―	7	―	―	―	―	―	7	―
.	7✕	.	.	.	.	.	7✕	.
.	.	.	.	.	.	.	.	.
.	7✕	.	.	.	.	.	.	.
.	.	.	.	.	.	.	7✕	.
―	7	―	―	―	―	―	7	―
.	7✕	.	.	.	.	.	7✕	.
.	.	.	.	.	.	.	.	.

Either the 7s go into (R2C2 & R7C8) or into the opposite diagonal (R2C8 & R7C2). In both diagonals, Columns 2 and 8 will each receive a 7 from these four corners. Therefore, all other 7s in Columns 2 and 8 (`7✕`) are eliminated!

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