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How to solve Sudoku?

Do you want to try your hand at Sudoku, but don't know where to start yet? Sudoku puzzles seem difficult as they contain numbers, but they are not really based on mathematics. You can easily solve Sudoku even if you don't have math skills. In fact, if you replace numbers with letters, the result remains the same. The point is to determine the correct order of the symbols. Start by learning the basics of solving Sudoku, and then familiarize yourself with simple tricks and more advanced techniques for solving these puzzles.

The basics of solving sudoku

Become familiar with the structure of the puzzle. Classic online Sudoku is a square field with a grid of nine large squares. Each large square is divided into nine more small ones. Initially in the puzzle, some small squares are filled with numbers from one to nine. The more difficult the Sudoku, the fewer numbers there are at the very beginning.

Large Sudoku squares are usually indicated by thicker lines, while smaller ones are usually indicated by thinner ones. Also, sometimes the background of large squares is painted in a checkerboard pattern.

Understand how rows and columns are built. The basic rule of the puzzle is to place numbers from one to nine in each row and column. This means that no digit in a row or column should be repeated.

Pay attention to the numbers in each large square. Likewise, all numbers from one to nine must be present in each of the large nine squares. Again, this means that each digit must appear in the large square only once, since it consists of only nine small squares.

Therefore, if there is already a two in the large square, there is no way to put another two in it.

Use a pencil, not a pen, to solve the web Sudoku puzzle. If you are just learning how to solve Sudoku, you cannot avoid mistakes, but they will be difficult to correct if you fill in Sudoku with a pen. Use a pencil instead of a pen so mistakes can be erased with an eraser.

Simple tricks

Check for large squares with one missing number on the board. Check each large square and see if there is one that is missing only one number. If such a square exists, it will be easy to fill. Just determine which of the numbers from one to nine is missing.

For example, a square may contain numbers from one to three and from five to nine. In this case, there is no four, which is required to be inserted into an empty cell.

Check for rows and columns with only one number missing. Go through all the rows and columns of the puzzle to find out if there are cases where only one number is missing. If there is such a row or column, determine which number from the row from one to nine is missing, and enter it in an empty cell.

If the column of digits contains numbers from one to seven and a nine, then it becomes clear that an eight is missing, which must be entered.

Look carefully at the rows or columns to fill in the missing numbers in the large squares. Look at a row of three large squares. Check it for two repeating numbers in different large squares. Swipe your finger along the rows that contain these numbers. The third large square should also contain this number, but it cannot be located in the same two rows that you traced with your finger. It should be in the third row. Sometimes two out of three cells in this row of the square will already be filled with numbers and it will be easy for you to enter the number that you checked in its place.

If there is an eight in the two large squares of the row, it must be checked in the third square. Slide your finger along the rows with the two eights present, since there cannot be an eight in these rows in the third large square.

Additionally, view the puzzle field in a different direction. Once you understand the principle of viewing the rows or columns of the puzzle, add a viewing in the other direction to it. Use the above viewing principle with a little addition. Perhaps when you get to the third large square, there will be only one ready-made number and two empty cells in the row in question.
In this case, it will be necessary to check the columns of numbers above and below the blank cells. See if one of the columns contains the same number that you are going to put. If you find this number, you cannot put it in the column where it already exists, so you need to enter it in another blank cell.

Work directly with groups of numbers. In other words, if you notice many of the same numbers on a field, they can help you fill in the rest of the squares with the same numbers. For example, there may be many fives on the puzzle field. Use the above field scan technique to fill in the remaining fives as much as possible.

Advanced tricks

Analyze blocks of three large squares in a row or column. Another option is to analyze three large squares at once in a column or in a row. Pick one number and see if you can fit it into all three squares.

For example, let's say you decide to take a six. Look at which rows or columns it is already in, and use this information to analyze the three big squares that you are currently interested in. Based on the information received and what is in the squares themselves, try to fill them with sixes as much as possible.

Mark the intended position of the numbers with a pencil. As the puzzles get more complex, the above techniques may not always be straightforward to find a solution. In such situations, you will need to start filling in the puzzle field with hypothetical numbers. When confronted with uncertainty, use a pencil to write the intended number in the corner of the cell. While solving the puzzle in the cells, you may have up to three or four suggested numbers.

In the course of the placement of the estimated numbers, you may be faced with the fact that only one single digit can be inserted into some cell, which will need to be immediately finally entered into its place.

Recheck cells regularly. As you fill in the puzzle, do not forget to re-view its field and return to those cells that you left empty earlier. When the puzzle is filled with any numbers, other empty cells can also find their solution.
When re-checking the blank cells, use the same techniques again to fill them in with numbers.


Double-check each number that you are going to enter in the next cell. A single mistake can confuse and ruin everything.

Related Resources:

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