X-Wing Sudoku Strategy

How the strategy works

If a candidate can appear in exactly the same two columns across two rows, those four corners form an X-Wing. That candidate can be removed from the rest of those columns.

The pattern can also work in reverse: two columns can lock a candidate into the same two rows.

Large print practice routine

Use this technique slowly on a readable board or a printed sheet. The goal is to remove uncertainty, not to solve faster.

After each candidate cleanup, return to scanning and singles before looking for another advanced pattern.

X-Wing should be a cleanup move, not the first thing a player searches for. It is most useful after the board has enough candidate notes to show repeated two-position patterns without covering the large numbers. If the candidate grid is sparse, return to singles first.

• Choose one candidate number.
• Scan rows for exactly two possible positions.
• Look for two rows that share the same two columns.
• Remove that candidate from other cells in those columns.

Example pattern

Example: candidate 6 can go only in columns 2 and 8 of row 3. In row 7, candidate 6 can also go only in columns 2 and 8. Those four cells form the rectangle.

Because rows 3 and 7 must use their two 6 placements in columns 2 and 8, any other 6 candidates in columns 2 and 8 can be removed.

Common mistakes to avoid

Do not use X-Wing when one of the rows has a third possible position for the same candidate. The pattern needs a clean two-position lock.

Do not remove every matching number from the board. Remove only that candidate from the affected columns or rows proven by the rectangle.