Sudoku Variants: 10 Types of Sudoku You Should Try
Classic 9×9 Sudoku is just the beginning. Discover the fascinating world of Sudoku variants — from Killer and Samurai to Thermometer and Sandwich — and find your next favorite puzzle challenge.
If you have been solving classic Sudoku for a while and feel like you have mastered the standard solving techniques, it might be time to explore the wider world of Sudoku variants. Over the past two decades, puzzle designers have created dozens of creative variations that add new rules, constraints, and dimensions to the classic 9×9 format.
Each variant preserves the fundamental satisfaction of Sudoku — using logic to place every digit — while introducing fresh challenges that keep your brain engaged. In this guide, we cover 10 of the most popular and rewarding Sudoku variants, from beginner-friendly options to mind-bending expert challenges.
1. Killer Sudoku
Combines Sudoku with Kakuro. Instead of given numbers, the grid has dotted cages with sum totals. You must place digits so each cage adds up to its target while following standard Sudoku rules. No digit can repeat within a cage.
Best for: Players who love arithmetic and want an extra layer of challenge.
2. Samurai Sudoku
Five overlapping 9×9 grids arranged in an X pattern. The overlapping regions must satisfy the rules of both grids simultaneously. With 369 cells to fill (compared to 81 in standard Sudoku), Samurai puzzles are a true test of endurance and spatial reasoning.
Best for: Experienced solvers looking for longer, more complex puzzles.
3. Thermometer Sudoku
Standard Sudoku rules apply, plus thermometer shapes are drawn in the grid. Digits along each thermometer must increase from the bulb to the tip. This constraint adds a directional ordering element that requires careful planning.
Best for: Players who enjoy inequality and ordering constraints.
4. Sandwich Sudoku
Clues outside the grid indicate the sum of digits between the 1 and 9 in that row or column. You must figure out where the 1 and 9 go, then determine which digits are "sandwiched" between them. A deceptively tricky variant.
Best for: Solvers who enjoy deduction chains and mental arithmetic.
5. Diagonal Sudoku (Sudoku X)
Standard Sudoku rules plus one extra constraint: both main diagonals must also contain the digits 1 through 9 without repetition. This simple addition significantly changes the solving dynamics and often makes puzzles easier by providing extra constraints.
Best for: Beginners looking for a gentle step up from classic Sudoku.
6. Hyper Sudoku (NRC Sudoku)
Adds four extra 3×3 boxes overlapping the standard grid (highlighted in a different color). Each extra box must also contain digits 1-9. The additional constraints actually make many puzzles easier to solve, making this a great variant for intermediate players.
Best for: Intermediate players wanting more constraint-based solving.
7. Jigsaw Sudoku (Irregular Sudoku)
Replaces the standard 3×3 boxes with irregularly shaped regions. Each row, column, and irregular region must contain digits 1-9. The non-rectangular shapes break familiar patterns and force you to think differently about eliminations.
Best for: Players who want to break out of standard solving habits.
8. Arrow Sudoku
Arrows are drawn in the grid. The digit in the circle at the base of each arrow must equal the sum of the digits along the arrow shaft. This creates powerful mathematical relationships that skilled solvers can exploit for elegant deductions.
Best for: Players who enjoy combining arithmetic with logical deduction.
9. Mini Sudoku (4×4 and 6×6)
Smaller grids that follow the same rules as standard Sudoku. 4×4 grids use digits 1-4 with 2×2 boxes, and 6×6 grids use digits 1-6 with 2×3 boxes. Perfect for beginners, children, and quick puzzle breaks.
Best for: Children, absolute beginners, and quick mental warm-ups.
10. Kropki Sudoku
The grid contains white and black dots between adjacent cells. A white dot means the two digits differ by 1; a black dot means one digit is double the other. The absence of a dot means neither relationship holds. No given digits — you start from the dots alone.
Best for: Advanced solvers who enjoy pure deduction without any given digits.
Start with the Fundamentals
Before diving into variants, make sure you have a solid foundation in classic Sudoku. The solving techniques you learn — from basic Naked Singles to advanced X-Wing patterns — transfer directly to most variants. Our how to play guide and tips page will get you up to speed quickly.
Once you can comfortably solve hard and expert classic puzzles, you are ready for the exciting world of variants. Start with Diagonal Sudoku or Hyper Sudoku for a gentle transition, then work your way up to Killer, Thermometer, and beyond.
Key Takeaways
- Sudoku variants add new rules to the classic 9×9 format for fresh challenges
- Killer Sudoku, Samurai, and Thermometer are among the most popular variants
- Diagonal Sudoku and Mini Sudoku are the best starting points for variant beginners
- Classic solving techniques transfer to most variants
- Switching between variants prevents mental autopilot and maximizes brain benefits
- Master classic Sudoku first before exploring variants
Frequently Asked Questions
What are the most popular Sudoku variants?
The most popular Sudoku variants are Killer Sudoku, Samurai Sudoku, Diagonal Sudoku (Sudoku X), Thermometer Sudoku, and Sandwich Sudoku. Killer Sudoku is arguably the most widely played variant after classic Sudoku, as it combines number placement with arithmetic in a satisfying way. YouTube channels like Cracking the Cryptic have also popularized Thermometer, Arrow, and Sandwich variants.
Which Sudoku variant is the hardest?
Kropki Sudoku and Samurai Sudoku are generally considered the most challenging variants. Kropki puzzles provide no given digits at all — you must deduce everything from dot relationships. Samurai Sudoku is demanding due to its sheer size (five overlapping grids). However, difficulty varies by puzzle, and even "easy" variants can have expert-level individual puzzles.
Are Sudoku variants good for brain training?
Yes, variants can be even better than classic Sudoku for brain training. Each variant introduces new constraints that force you to develop different problem-solving strategies. This novelty is important for cognitive benefits — research shows that the brain benefits most when it encounters challenges that are both familiar enough to engage with and novel enough to require new thinking. Switching between variants prevents your brain from running on autopilot.
What is the best Sudoku variant for beginners?
Mini Sudoku (4×4 or 6×6 grids) is the best starting point for absolute beginners and children. For players who already know classic Sudoku, Diagonal Sudoku (Sudoku X) is the gentlest variant because it adds just one rule (diagonals must also contain 1-9) and the extra constraint actually makes puzzles easier to solve. Hyper Sudoku is another beginner-friendly variant.
Where can I play Sudoku variants online?
Many Sudoku apps and websites offer variants alongside classic puzzles. For now, our platform focuses on delivering the best classic Sudoku experience with AI-powered solving and step-by-step hints. Master the fundamentals with our easy to expert puzzles and solving techniques, then explore variants when you are ready for a new challenge.
Do Sudoku variants use the same solving techniques?
Many classic techniques like Naked Singles, Hidden Singles, and Naked Pairs apply to all variants. However, each variant also requires unique strategies specific to its extra constraints. For example, Killer Sudoku requires "cage sum" logic, Thermometer Sudoku requires "thermometer ordering" deductions, and Sandwich Sudoku requires "sandwich sum" reasoning. Learning classic techniques first gives you a strong foundation for any variant.