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Expert Sudoku level

The next stage after hard puzzles are expert Sudoku level differing from the previous type in that there are even more blank cells in the grid, and the number of digits filled in some of the cells is even less. To solve them, the player will need all the interface elements available: notes, canceling moves, erasing digits in the applicable cells, clues (you can find out more about interface free Sudoku), as well as using different types of strategies.

The objective of the game

The objective is to fill the blank cells of a 9х9 grid within a minimum time, using the given set of digits from 1 to 9, in such a way that each 1х9 row, 1х9 column and 3х3 region do not contain duplicate digits.


To solve the most hardest Sudoku puzzles (online on this website and without having to register), you will need to employ all the strategies you have previously learned. Start with the ones you first used on easier levels, and "run" through all the grid cells until you master the XY-Wing strategy technique. After doing that, you will definitely find the solution for at least one cell. Searching for a digit’s location opens up new opportunities every time, you should constantly repeat these devices. Try switching every time from easy to hardest and from expert to easy in order to continue finding the hidden digits and determining new candidates for the cells.

Making notes is the main requirement for solving expert Sudoku, but don’t forget to update and clear them every time you enter a digit in a cell, for the further course of solving to become easier time after time.

Most common mistakes

When solving hardest Sudoku, just like any other ones, every new player encounters mistakes which they must pay attention to:

  1. Attempting to take guesses. You should use logic to solve the puzzle, instead of taking guesses. It is very easy to enter a digit at a venture, even if the player cannot find a logical reason for that. But an incorrect assumption can make the free online expert Sudoku puzzle unsolvable. In most cases, such a mistake becomes obvious only at the very end of the game when the user finally finds an inadmissible or duplicate digit. All the time and effort will be spent in vain then.
  2. Failing to use the "notes" function when it is really necessary. Easy levels can be solved without using the notes function. All it takes to complete the layout is elementary logic and a sufficient degree of concentration. Meanwhile, more complex ones cannot be solved without this function. Some newbies wrongly believe that notes are an instrument for cheating when solving Sudoku puzzles. But that isn’t so. It’s not about cheating. It’s about providing your brain with an opportunity to analyze multiple variants and ways at a time and stimulating its cognitive development.
  3. Failing to update the notes. Many mistakes occur because you just forget to update them after finding the right location for the intended candidate in a particular cell.

The puzzle’s advantages

  1. It teaches you to think outside the box, using logic and logical chains of reasoning. When entering a digit in a particular blank cell, you analyze the ones that have already been filled in, and take account of the rules in accordance with which the rows, the columns, and the 3х3 regions must be filled in. Every decision is made with involvement of logic.
  2. It develops your rationalization skills. The player is posed with a task to solve the puzzle and rationally consider each move and decision. Will this work? Will that be appropriate? Why yes, or why not? If you "place" this digit here, what impact will it have on the other digits?
  3. It teaches you to look for and identify patterns (templates). Just like in most games of this kind, templates may play an important role. In some cases, you can see a regularity when looking at a puzzle. Such regularities allow for reducing the time before the successful completion of the puzzle.
  4. It improves your memory. The game requires you to constantly memorize the puzzle pieces. You bear in memory what you have and what you need to complete a row, a column, or a region.
  5. It develops your attention, concentration, and patience. Solving a puzzle may be a challenging task. To complete it, you will need to concentrate and to arm yourself with patience. This requires many brain parts to focus (concentrate) using logic and reasoning to determine the next move (the solving course). The main thing is patience. Learn from your mistakes, thus developing your brain. The trial-and-error method is an excellent way to become better, more persistent, and more experienced.
  6. It improves your reaction time. When you just begin to play, at the very beginning, your reaction time is very long because you have very little experience in puzzle solving. But as you solve puzzles more often and enhance your game skills you will feel that your reaction time improves from day to day. It will also impact your real life where your reaction time will be much better than before.