Sudoku #6794

01 March 2024

How to play sudoku?


  1. Choose the sudoku difficulty level you like from the drop-down menu at the top. You have 7 levels to choose from very easy to very hard, including magic sudoku.
  2. Fill in the boxes. You can do this by clicking on the box directly or by selecting the box you want and clicking on the numeric keypad on the right.
  3. When you finish filling in all of them, if you have done it right, a message will be displayed congratulating you. If you have doubts about whether you have filled in the sudoku correctly while you are doing it, you can use the self-check function that will warn you of the possible mistakes you make.

If at any time you want to check your numbers you can do so by clicking on the check button. You can also display the sudoku solution or start over. Good luck!

What is Sudoku?


The Sudoku, also known as südoku, su-doku or su doku, is the fashionable Japanese logic puzzle. The history of sudoku is quite recent, although in the 19th century some French newspapers already proposed similar number puzzles, it was not until the 1970s that the sudoku we know today was developed in Japan. Since 2005 (when started) this logical game started to become popular internationally. The word sudoku in Japanese means (sü=number, doku=solo).

Sudoku rules and difficulty

The rules are simple, it consists of a grid of 9x9 cells, divided into 9 quadrants of 3x3, which must be filled so that all rows, columns and quadrants (sets of 3x3 cells) have the numbers from 1 to 9 without any repetition. Obviously, the starting point is a board with some known positions. In general, the less initial numbers a sudoku has, the more complicated it is, but don't be fooled. The difficulty is not only determined by this variable. At we always try to make sure that the sudokus we generate are the most fun and with a perfectly adapted difficulty.

Obviously you start from a started board. In order to be correct, Sudokus must have an unique solution.


It is curious, but in 2012 it was mathematically demonstrated that for a sudoku to have a single solution it must have at least 17 initial positions. There are a multitude of scientific articles and publications that try to determine how many sudokus exist, how many options there are and how to solve them in the most efficient way.


Sudokus are combinatorial problems ideal for developing logical thinking. They help to keep the mind active and it is an excellent entertainment to maintain mental agility, especially with numbers. It also helps to keep your memory sharp as the more complicated sudokus require you to make guesses that force you to evaluate different options. Also if you are just starting to program Sudokus are a classic problem for programming students.

And Magic Sudoku?

The Magic Sudoku is a variant of the traditional sudoku. It is characterized by adding the following restrictions to the original sudoku:

This Sudoku is more complicated, but also much more challenging and fun, are you up for it?

Free Sudokus to play online, print and download.
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