Sudoku Techniques: X-Wing

On the road to becoming a more proficient Sudoku player, learning several strategies and techniques to solve Sudoku puzzles more effectively is essential. Once you’ve learned the basics of the game through easy Sudoku games, such as the terminologies and the mechanics, you can now begin trying out several effective strategies and techniques in Sudoku.

X-Wing, also known as the rectangle trick, is one of the most commonly used tactics by Sudoku players in completing a grid. Continue reading to learn what it is, how to use it and other Sudoku tips!

What Is the X-Wing in Sudoku Puzzles?

X-Wing in Sudoku Puzzles
X-Wing in Sudoku Puzzles

The X-Wing is a technique used in solving medium Sudoku puzzles and still can be used for harder difficulties, which commonly have fewer givens and rely more on the player making use of candidates and notes (which is also a feature in Sudoku Conquest as you can enter multiple numbers into a cell).

It’s named as it is due to the X-like pattern it creates in the grid of the game.

The X-Wing is great at removing duplicate numbers and finding patterns in the logic of your Sudoku puzzle. However, it’s important to note that not every puzzle can effectively be solved with just one technique like the X-Wing, but partnered with other strategies, it becomes a very useful tool to remember.

To do the X-Wing, it’s ideal to fill or pencil-mark candidates into all cells first, as this will make the overall solving process easier and more efficient. Once that’s done, it’s time to choose common candidates and start eliminating them using the X-Wing.

For example, you have the number 5 recurring as a candidate in r4c4, r6c4, r4c7 and r6c7. Once you identify these four candidates, you can see that they form a rectangle of cells—hence why it’s called the rectangle rule. These four numbers act as the corner of the rectangle, and can also be connected with an X between them.

How Does It Work?

How does X-Wing work?
How does X-Wing work?

The X-Wing relies on logic between the four identified cells sharing the same candidate digits. In this case, the number 5 repeats in cells r4c4, r6c4, r4c7 and r6c7. The X in the technique’s name is also due to the relationship between these cells.

In this case, cell r4c4 is connected to r6c7 while r6c4 is with r4c7. If you choose number 5 in r4c4 and consider it to be correct, then the digit 5 in r4c7 is to be eliminated since one of the rules of Sudoku requires you to remove duplicates in the same row or column.

Since r4c4 is connected to r6c7, the correct number 5 for the entirety of row 6 and column 7 is r6c7. This can also be used inversely as well. If the 5 in r6c4—which is connected to r4c7—is considered correct, then the other end of the X is logically true as well.

Candidate Elimination After Using X-Wing

Candidate Elimination
Candidate Elimination

Once you choose the cells containing the right numbers for your Sudoku logic using X-Wing, you can then remove the other existing cells with the same digits in their candidates.

Now, back to our example with the cells r4c4, r6c4, r4c7 and r6c7. If the 5 in both r4c4 and r6c7 are considered correct, all the other candidates in the same row and column can now be removed.

With this technique, you have now effectively removed possible logic errors in those rows and columns, and puts you one step closer to completing your Sudoku puzzle!

Why Candidate Elimination Matters in Free Sudoku Puzzles

It is crucial to remember that the main objective of Sudoku is to solve a completed grid with an answer that has no repeating numbers between 1 to 9. X-Wing is a great trick to use to make the process of elimination faster (which is the most time-consuming and challenging part of the game) and fill in cells easier.

Incorporating X-Wing Into Your Style

There’s no set way on how you will fit X-Wing into your Sudoku style, but by learning it, you can define your own system and play as you see fit. Most of the time, X-Wing works well with Sudoku players who like using trial-and-error logic to solve their puzzles but is just as effective for people who like reading patterns as their main playing strategy. Keep in mind that there are other techniques to learn as well, such as the Y-Wing.

For now, up your game and try this technique out in an easy Sudoku puzzle created on our site,!