The Most Difficult Sudoku, Ranked

Voting rules: Choose the Sudoku you think is the most difficult!

Updated on Apr 28, 2024 06:26

Solving Sudoku presents a delightful challenge that tests our minds in new and complex ways. Among these numerical puzzles, the most difficult ones stand out because they push our logical thinking and patience to the limits. Understanding which Sudokus are the toughest can help enthusiasts find puzzles that provide not only an enjoyable pastime, but also a satisfying intellectual conquest. Voting on these challenging puzzles serves a dual purpose. First, it helps to identify and confirm which Sudokus are truly the hardest, creating a valuable resource for those in search of the ultimate test. Additionally, your participation shapes this continually updated list, making it a reliable guide for puzzle lovers around the world looking for a real challenge to their abilities.

What Is the Most Difficult Sudoku?

1

86
votes
AI Escargot

Arto Inkala

This Sudoku puzzle is considered the most difficult one ever created. It was created by Finnish mathematician Arto Inkala and has been rated as a level 11 on a scale of 1 to 10 in terms of difficulty. The puzzle has gone viral and has been attempted by thousands of Sudoku enthusiasts worldwide.
The AI Escargot is widely considered the most difficult Sudoku puzzle ever created. It gained this reputation due to its intricate and complex solution process.

Grid Size: 9x9

Number of Clues: 17

Difficulty Level: Extreme

Solution Complexity: High

Solution Techniques: Advanced and intricate
2

20
votes
The Monster

This Sudoku puzzle was created by Thomas Snyder and is also considered one of the most difficult puzzles ever created. It was rated as a level 10 on a scale of 1 to 10 in terms of difficulty. The puzzle has a unique shape and is made up of 1,000 squares.
The Monster is one of the most difficult Sudoku puzzles ever created. It is known for its incredibly challenging layout and intricate solving process, requiring advanced techniques and strategies. The puzzle has gained notoriety among Sudoku enthusiasts for its high level of complexity.

Difficulty Level: Extremely Hard

Grid Size: 9x9

Number of Clues: 17

Unique Solution: Yes

Symmetry: Diagonal Symmetry
The Monster in other rankings
- Position 10 of 10 in Most popular Eddsworld character
3

34
votes
The Hardest Sudoku Ever

Arto Inkala

This puzzle was created by Japanese puzzle maker Maki Kaji and was rated as a level 11 on a scale of 1 to 10 in terms of difficulty. The puzzle is unique in that it has multiple solutions, making it even harder to solve.
The Hardest Sudoku Ever is a puzzle that has gained notoriety for its exceptionally challenging nature. It is designed to push the limits of Sudoku solvers and is often considered one of the hardest puzzles to solve.

Brute Force Solvability: No

Sudoku Variant: Standard Sudoku

Unique Solution: Yes

Logical Solvability: Yes

Grid Size: 9x9
4

15
votes
Sudoku X

Howard Garns

This variation of Sudoku is considered one of the most difficult versions of the puzzle. It has the same rules as a regular Sudoku but also has two diagonal lines that must contain the digits 1 to 9 without any repetition.
Sudoku X is a variant of the classic Sudoku puzzle that incorporates an additional diagonal constraint. It is played on a 9x9 grid, divided into nine 3x3 boxes. The goal is to fill in each cell of the grid with a number from 1 to 9, making sure that every row, column, 3x3 box, and both main diagonals contain each number only once.

Grid size: 9x9

Boxes: 9

Number range: 1 to 9

Constraints: Rows, columns, 3x3 boxes, main diagonals

Additional constraint: Diagonals must also contain each number only once
5

10
votes

Killer Sudoku

This variation of Sudoku is also considered one of the most difficult versions of the puzzle. It has the same rules as a regular Sudoku but also includes groups of cells that must add up to a certain number.
6

11
votes
Jigsaw Sudoku

Wayne Gould

This variation of Sudoku is also considered one of the most difficult versions of the puzzle. It has the same rules as a regular Sudoku but also has irregularly shaped regions that must contain the digits 1 to 9 without any repetition.
Jigsaw Sudoku is a variation of traditional Sudoku that adds an additional layer of complexity by dividing the puzzle into irregularly shaped regions called jigsaw boxes. Each box must contain all the numbers from 1 to 9, and all the regular Sudoku rules still apply within each row, column, and box.

Box Shape: Irregular jigsaw-shaped boxes.

Board Size: 9x9 grid.

Number Range: Numbers 1 to 9.

Difficulty Levels: Various difficulty levels available.

Clues: Some cells are initially filled as clues.
7

6
votes
Windoku

This variation of Sudoku is also considered one of the most difficult versions of the puzzle. It has the same rules as a regular Sudoku but also has four overlapping grids that must contain the digits 1 to 9 without any repetition.
Windoku is a variant of Sudoku that adds a twist to the traditional 9x9 grid by incorporating diagonal regions. The puzzle is named after its creator, Oskar van Deventer. It is known for being one of the most challenging Sudoku variations available.

Grid Size: 9x9

Regions: Rows, columns, 3x3 boxes, and diagonal regions

Difficulty: Very difficult

Initial Clues: Usually around 20-25 clues

Rules: Fill the grid so that every row, column, 3x3 box, and main diagonal contains the digits 1 to 9
8

10
votes
Sudoku 16x16

This variation of Sudoku is also considered one of the most difficult versions of the puzzle. It has the same rules as a regular Sudoku but also has a larger grid with 16 rows and columns.
Sudoku 16x16 is a variant of the classic Sudoku puzzle that is played on a 16x16 grid instead of the traditional 9x9 grid. This larger grid size increases the complexity and challenge of the puzzle.

Grid Size: 16x16

Number of Cells: 256

Number of Clues: varies (typically fewer than 40)

Difficulty Level: extremely challenging

Row Constraints: unique numbers from 1 to 16
9

7
votes
Sudoku 25x25

This variation of Sudoku is also considered one of the most difficult versions of the puzzle. It has the same rules as a regular Sudoku but also has a larger grid with 25 rows and columns.
Sudoku 25x25 is a complex variation of the popular Sudoku puzzle, played on a grid of 25x25 cells instead of the traditional 9x9 grid. It presents a significant challenge due to the larger grid size and increased number of cells and possibilities.

Grid Size: 25x25

Total Cells: 625

Block Size: 5x5

Difficulty Level: High

Number of Clues: varies, but usually 32 or less
10

8
votes
Sudoku Variants

Nikoli Co., Ltd.

There are countless variations of Sudoku that can make the puzzle even more difficult, such as Diagonal Sudoku, Outside Sudoku, Irregular Sudoku, and more. Each variation adds a new layer of complexity to the puzzle, making it more challenging for even the most experienced Sudoku solvers.
Sudoku Variants is a collection of Sudoku puzzles with different variations from the classic Sudoku game. These variants introduce new rules or patterns that make the puzzles more challenging and engaging. Each variant offers a unique twist on the original Sudoku concept.

Varieties: Multiple variants available

Difficulty Levels: Varies from easy to extremely difficult

Grid Size: Usually 9x9, but can vary

Additional Rules: Additional constraints or patterns to solve

Symmetry: May or may not have symmetric patterns

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Discussion

Ranking factors for difficult Sudoku

Number of given clues

Generally, Sudoku puzzles with fewer given clues are considered more difficult because they provide less information to start solving the grid.
Distribution of the given clues

If the given clues are evenly distributed across the Sudoku grid, it can be easier to find the logical steps to fill in the remaining numbers. In contrast, if the clues are clustered in one area, the solving process can be more challenging.
Unique solutions

A valid Sudoku puzzle should have only one unique solution. If a puzzle has multiple solutions, it may be considered difficult, as the solver may need to rely on trial and error to find the correct solution.
Complexity of solving techniques

Solving a Sudoku puzzle often requires the use of logical techniques to deduce the placement of numbers. Some puzzles may require more advanced techniques, such as X-Wing, Swordfish, or even Guessing and Backtracking, which can increase the difficulty level.
Number of steps to solve the puzzle

A Sudoku puzzle that requires a larger number of logical deductions to be solved can be considered more difficult than a puzzle that can be solved with fewer steps.
Level of interdependence between cells

In some Sudoku puzzles, the placement of numbers in one region heavily depends on the placement of numbers in another region. These puzzles are often more difficult to solve, as they require the solver to consider a larger set of cells or perform more complex deductions simultaneously.

About this ranking

This is a community-based ranking of the most difficult Sudoku. We do our best to provide fair voting, but it is not intended to be exhaustive. So if you notice something or Sudoku is missing, feel free to help improve the ranking!

Statistics

3866 views
189 votes
10 ranked items

Voting Rules

A participant may cast an up or down vote for each Sudoku once every 24 hours. The rank of each Sudoku is then calculated from the weighted sum of all up and down votes.

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More information on most difficult sudoku

Sudoku, a popular number-based puzzle game, has been a favorite pastime for many people around the world. It is a game of logic and problem-solving where players must fill a 9x9 grid with the numbers 1 to 9, without repeating any number in a row, column, or 3x3 sub-grid. While Sudoku may seem like a simple game, the difficulty of each puzzle can vary greatly depending on the number of clues given and their placement on the grid. The most difficult Sudoku puzzles often require advanced problem-solving techniques and can take hours to complete. Many Sudoku enthusiasts have even created their own rankings and classifications for the difficulty of puzzles, with some claiming that the hardest Sudoku puzzles can only be solved by the most skilled players.