The X-Wing Technique Explained (with Examples)

The X-Wing is the technique that separates intermediate Sudoku solvers from advanced ones. Once you learn it, a whole category of hard puzzles becomes solvable — and the logic is elegant once you see why it works.

What Problem X-Wing Solves

Before X-Wing, you use naked singles, hidden singles, pointing pairs, and naked pairs. These find where a digit must go within a single row, column, or box.

X-Wing works differently. It looks across two rows and two columns at once to prove where a digit cannot go. That elimination then unlocks other techniques.

The X-Wing Pattern

Step 1: Pick a digit — let’s use 7. Go through every row and count how many cells can hold a 7.

Step 2: Find two rows where 7 can only go in exactly two cells, and those two cells are in the same two columns in both rows.

Those four cells form a rectangle:

         Col 3       Col 7
Row 2:   [7?]        [7?]
Row 6:   [7?]        [7?]

Step 3: Think about what must happen. Row 2 needs a 7 — it can only go in Col 3 or Col 7. Row 6 also needs a 7 — same two options.

Two outcomes are possible:

Row 2 gets 7 in Col 3, Row 6 gets 7 in Col 7.
Row 2 gets 7 in Col 7, Row 6 gets 7 in Col 3.

Either way, Col 3 gets exactly one 7 and Col 7 gets exactly one 7 — both from within those two rows.

Step 4 — Eliminate: Every other cell in Col 3 and Col 7 (outside Rows 2 and 6) cannot hold a 7. Remove 7 from their candidate lists.

Worked Example

We are tracking digit 7 in this grid. Most rows have 7 already placed (shown in gray). Only Rows 2 and 6 are still missing a 7.

In Row 2, checking every cell: 7 has been eliminated from columns 1, 2, 4, 5, 6, 8, and 9 by boxes and other constraints. Only Col 3 and Col 7 can hold a 7 in Row 2.

In Row 6, same check: only Col 3 and Col 7 remain. X-Wing confirmed.

Eliminate: Remove 7 from every other cell in Col 3 and Col 7 (all rows except 2 and 6).

Full 9×9 grid. Gray 7s show where 7 is already placed in other rows. In the two highlighted rows (2 and 6), digit 7 can only go in columns 3 and 7 (blue cells). Every other cell in those two columns can eliminate 7 (red ×).

After this elimination, naked singles or hidden singles may appear and unlock further progress.

How to Find X-Wings: Step-by-Step

Pick a digit. Start with digits that already appear 5–7 times — fewer remaining placements means fewer candidate cells.
Scan each row. For each row, count how many cells can hold the digit. Write down every row where the count is exactly 2.
Compare columns. For each pair of “2-candidate” rows, check if their candidate cells are in the same two columns. If they are, you have an X-Wing.
Eliminate. Remove the digit from every other cell in those two columns (all rows except the two X-Wing rows).
Try columns too. If row-based X-Wing does not help, scan columns for the same pattern: two columns where the digit appears in exactly the same two rows. Then eliminate from those two rows.

Common Mistakes

One row has more than two candidates.
The X-Wing requires exactly two candidate cells per row. If a row has three possible positions, there is no X-Wing in that row.

Columns do not match.
Both rows must use the same two columns. Row 2 has 7 in cols 3 and 7, but Row 6 has 7 in cols 3 and 8 — no X-Wing.

Eliminating from the wrong cells.
Eliminate from all other cells in the two columns. Do not eliminate from the X-Wing rows themselves.

When to Look for X-Wings

Try X-Wing after you have used:

Naked and hidden singles
Pointing pairs and box-line reduction
Naked pairs and triples

If the puzzle feels stuck and is rated “hard” or “expert,” check each digit for X-Wing. Start with digits that appear 6–8 times already.

Beyond X-Wing

Once X-Wing clicks, the related patterns are within reach:

Swordfish — three rows and three columns. Same logic, bigger rectangle.
Jellyfish — four rows and four columns. Rare but powerful.
Y-Wing — a chain of three cells that forces an elimination. More flexible, no rectangular requirement.

These are covered in the complete Sudoku solving guide.

Frequently Asked Questions

Q: Is the X-Wing named after the Star Wars fighter?
The four candidate cells form an “X” shape on the grid — the name stuck in the Sudoku community.

Q: Can X-Wing place a digit directly?
No. X-Wing is an elimination technique. It removes a candidate, which then lets placement techniques (naked or hidden singles) work.

Q: What if I have three rows with exactly two candidates?
Check if all three rows span the same three columns — that would be a Swordfish.

Q: Does X-Wing work column-first?
Yes. Find two columns where the digit appears in exactly two rows each, and those rows are the same. Eliminate from those two rows.

Q: How do I know if a puzzle needs X-Wing?
Hard-rated puzzles often need at least one X-Wing. If you have used all intermediate techniques and are still stuck, check for X-Wing on each digit.

What to Try Next

How to Solve Sudoku: Complete Guide — Full technique ladder including Swordfish, Y-Wing, and beyond.
Naked Singles and Hidden Singles: Sudoku’s Foundation — Strengthen the fundamentals X-Wing builds on.
Sudoku for Beginners: 5 Simple Rules — Start here if you are newer to the game.
How to Solve Logic Grid Puzzles — A different logic puzzle with similar elimination thinking.

Puzzmint is a calm, ad-free daily logic puzzle hub. Try today’s Sudoku →