Were you also scratching your head when you first started playing Sudoku? I, too, experienced the same thing because it is too tricky for me to finish. At first, it seems easy to fill in, but I find it confusing and complicated as I go along.

Learning one strategy at a time while playing Sudoku will help you hone your skills over time. For example, once you locate where a hidden single number should be placed, everything will flow naturally. A hidden single in Sudoku is the number candidate you need to put in an area to lock its placement in its inner box, column, and row.

Continue reading in the next section to find tricks to locate this hidden single in your Sudoku.

what is a hidden single in sudoku

What is a hidden single in Sudoku?

A hidden single in Sudoku is the sole number that could only be put in a specific area to complete the number combinations in its row, column, and inner box.

It is called “hidden single” because you’re the one who needs to put that single digit in its rightful place.

Most of the time, it is the most specific number to find in Sudoku. Usually, it serves as a clue for you to start completing the whole puzzle. However, when you start filling in the numbers already, you’ll experience some difficulties because some areas may have two or more possible numbers to put in.

In this case, it’s highly advisable to use erasable material like a pencil to mark it out or use another pen color to avoid confusion. You can check out my tips on how to get along with your Sudoku at this link: https://puzzlingcut.com/what-is-the-trick-to-solving-sudoku-puzzles/.

Now, before we dive into the tricks to step up your Sudoku skills, let’s have a quick run-through about its parts.

What are the parts of Sudoku?

Sudoku’s parts are plain and simple.

Most of the time, you’re not bound to “master” the terms because it’s unnecessary when solving the puzzle; however, if you want to step up your Sudoku skills, you must learn these words to understand the discussions at their advanced levels.

There are five parts of Sudoku that you should be aware of. The rows, columns, inner box (sometimes called block), givens or available numbers, and lastly, the blanks or spaces.

There are nine rows and nine columns in Sudoku. These rows are columns are divided into nine inner boxes or blocks of 3×3 grids.

The givens are the as available numbers generated by a computer. These are spread out in Sudoku grids at random.

And lastly, the blanks or spaces are the ones you need to logically analyze to know what appropriate number should be put in.

Now, to precisely locate a blank area in Sudoku, you need to identify its row, column, and inner box number. You can do this by numbering first its rows with 1 to 9 starting from the top, its columns with 1 to 9 starting from left to right, and its inner boxes with 1 to 9 starting from the topmost left one.

Then, identify the blank area with its row number first, followed by its column number. Most of the time, row and column number is enough to know where it is, but sometimes, you need to add their inner box number too so that you’ll know if that number candidate is also required for that particular group.

Here is an example for your reference.

parts of sudoku
**Note: Numbers in yellow color are the inner boxes or blocks

At what exact area can you find all the given numbers 7 in this example? Share your answers in the comment section below.


How to find hidden single in Sudoku?

Now that you know how to locate numbers in Sudoku let’s dig into how to find some hidden singles.

Finding the hidden single in Sudoku is easy but unnoticeable. Most of the time, looking for the hidden single is done by beginners in the easy level of Sudoku.

The technique is usually done using the cross-hatching method or the scanning method.

In my experience, I use the cross-hatching method because it’s much more manageable.

Beginners commonly use the cross-matching technique without even knowing what it’s all about, but it’s alright. What matters most is the completion of the puzzle.

So, the cross-matching method in Sudoku means that a player should cross out (imaginary crossing out the area) the rows or columns where a given number is already in place; then, whatever blank space is available to put that same number, that’s where it should be.

Here’s an example of a simple cross-matching method for your guide.

cross matching method
Cross-matching method for number 3. All red lines indicate that those areas should not have any 3’s in them.

On the other hand, the scanning method is a technique where you can disregard the specific numbers present but instead use a logical or imaginary assignment of only two identities present in your Sudoku puzzle, namely, the area with a number and without a number.

In the scanning method, you need to use your creativity and spatial reasoning to identify the area where you need to put the number candidate.

Now, to do this, scan the whole grid first and identify the placement of a number that caught your attention according to its inner box group and rows. Columns may not be considered in this part to make it more simple.

In this way, all you need to imagine is that you have nine inner boxes with nine major rows.

Therefore, having this image in your mind, we can say that there are only several number placements a single number can have.

guide for scanning method
Inner boxes are numbers in yellow color.

This will give you the idea that a certain number can or cannot be placed in a blank based on your logical reasoning.

Try completing this Sudoku puzzle using the two techniques discussed above.



Sudoku has many different strategies for finding hidden singles.

Cross-hatching and scanning method are proven techniques to find the hidden single.

The challenge is to look for the easiest one with which you’re personally comfortable and apply it to each puzzle.

I hope this article helped you understand how to solve sudoku puzzles!


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