30 Sudoku Variants That Completely Reinvent the Classic Grid

Sudoku looks deceptively simple on the surface. Nine digits, 81 cells, three rules. Then someone draws a jagged line across the grid, writes a small number in the corner, or shades a ring of cells, and nothing behaves the way you expect anymore. That is how variant Sudoku was born, and once you see how many directions the puzzle has gone, the standard version starts to feel like an entry point rather than a destination.

How Variants Became Their Own Solving World

Sudoku arrived in newspapers and magazines in the early 2000s and spread fast. Puzzle designers, not satisfied with a single rule set, began experimenting almost immediately. The key insight was that any extra constraint interacting with the existing rules creates genuine new logic rather than just a harder version of the same deductions. A line that forces high numbers away from certain cells changes which moves are valid everywhere else on the grid, not just along the line itself.

Many of these variants now appear in international events hosted by the sport's global puzzle federation, where competitors face them under timed conditions. The same variants also fuel a large online community of setters and solvers who share puzzles and work through them on video, building a shared vocabulary of techniques that did not exist two decades ago.

What Every Solver Should Know Before Trying a Variant

Each entry below explains the defining rule in plain terms, but a few habits apply across almost all variants and save a great deal of frustration early on:

• Absence is information. Many variants define what a cell cannot hold just as much as what it can. Learning to treat missing options as positive clues is the biggest shift from standard solving.
• Start with the most constrained cells. Variants stack rules, so some cells carry restrictions from three or four different sources at once. Those cells are almost always the best places to begin.
• Read every rule before placing anything. Missing one rule and placing a wrong digit can push the grid into a state that is very hard to trace back without starting over entirely.
• Skills carry between variants. Thermometer logic reappears inside Between Lines puzzles. Renban and German Whispers share underlying structural thinking. Time spent on one variant quietly builds toward the next.

Variants That Reshape or Expand the Standard Grid

These six variants keep the digit rules largely intact but change the physical layout of the grid itself, which means familiar logic stops working in familiar places.

1. Diagonal (X) Sudoku. The two long diagonals of the grid become additional regions, each requiring the digits 1 through 9 exactly once. Many cells now belong to four constraints at once: a row, a column, a box, and a diagonal, which makes every placement carry far more weight than it would in a standard grid.
2. Irregular (Jigsaw) Sudoku. The standard 3x3 boxes are replaced by nine irregular, jigsaw-shaped regions of the same nine-cell size. The core rule is unchanged, but the visual anchor of neat squares disappears entirely, forcing solvers to trace odd, winding boundaries instead of the familiar grid structure.
3. Samurai Sudoku. Five overlapping 9x9 grids share corner sections to create one enormous interlocking puzzle. A breakthrough in one grid ripples through the shared corner cells and frequently cracks open a neighbouring grid without any additional effort from the solver.
4. Hyper Sudoku. Four extra 3x3 boxes sit inside the main grid, offset from the standard boxes so that each extra box overlaps two of the original nine. The overlap drastically shrinks how many digits can fit in those shared cells, creating surprisingly tight restrictions right in the middle of the puzzle.
5. Windoku. Four shaded 3x3 regions are placed symmetrically inside the grid in a windmill arrangement, each acting as an additional box constraint. The precise placement means every standard box overlaps with at least two of the shaded regions simultaneously, linking distant parts of the grid through shared cells.
6. Sohei Sudoku. Three 9x9 grids are arranged in a diagonal chain, with each adjacent pair sharing a corner section. The layout is related in spirit to Samurai Sudoku but the long diagonal arrangement creates a very different solving rhythm and a different set of pressure points where the grids connect.

Variants Built Around Arithmetic and Sums

These six variants require cells to add up, balance, or compare against each other in specific ways, layering arithmetic directly onto the standard placement rules.

7. Killer Sudoku. Dotted cages group cells together, and each cage carries a target sum that its digits must reach exactly. No digit can repeat within a cage, which turns every placement into both a logic problem and an arithmetic one running at the same time.
8. Little Killer Sudoku. Numbers appear in the margins alongside diagonal directions and give the combined total of all digits on that diagonal. Unlike standard Killer cages, these diagonals can contain repeated digits, meaning the arithmetic alone cannot nail down individual values without additional reasoning from the rows and columns.
9. Sandwich Sudoku. A number outside each row or column tells you the sum of all digits sitting between the 1 and the 9 in that line. The puzzle begins by hunting for where the 1 and the 9 must land, because nothing in the middle can be determined until those two anchors are placed.
10. Arrow Sudoku. Circles with arrows sit on the grid, and the digit in each circle must equal the sum of all digits along its arrow's path. A single arrow can weave across rows, columns, and boxes at once, creating arithmetic links between distant parts of the grid that would otherwise seem completely unrelated.
11. XV Sudoku. An X printed between two adjacent cells means they sum to 10, and a V means they sum to 5. Not every adjacent pair is marked, but each marked pair must satisfy its target exactly, while the unmarked pairs fall back to standard row-and-column logic with no extra restriction.
12. Greater Than Sudoku. Inequality signs between adjacent cells show which of the two must be the larger value. The purest versions of this variant provide no given digits at all, meaning every deduction comes purely from following the directional arrows without any numbered starting points on the grid.

Variants That Draw Lines Across the Grid

These six variants add drawn lines, bulbs, or endpoint markers that impose rules on sequences of connected cells. The line is almost always the most productive place to begin solving.

13. Thermometer Sudoku. Bulb-and-stem thermometer shapes cross the grid, and digits must increase strictly from the round bulb end to the pointed tip. A cell near the tip cannot hold a low digit, and a cell near the bulb cannot hold a high one, which eliminates a large portion of options before any other rule is applied.
14. Renban Sudoku. Coloured lines mark groups of cells that must together contain a set of consecutive digits in any order along their path. A five-cell Renban line must hold any five consecutive numbers, such as 3, 4, 5, 6, 7, scrambled in whatever arrangement fits the surrounding constraints.
15. German Whispers Sudoku. Any two cells sharing a segment of the marked line must hold digits that differ by at least 5. German Whispers Sudoku creates cascading constraints across the grid because a high digit forces its neighbour on the line to be low, that low digit then forces the next cell to be high again, and this wave of alternating pressure runs from one end of the line to the other.
16. Dutch Whispers Sudoku. A close relative of the German version, Dutch Whispers requires adjacent cells along its line to differ by at least 4. The rule is slightly more relaxed but still generates long chains of restricted placements that ripple outward from the line into the surrounding grid.
17. Between Lines Sudoku. A line with a filled circle at each end means every digit along the line must fall numerically between the two endpoint values. A long line anchored between a 2 and an 8 at its ends cannot hold a 1, a 9, or anything outside that range in any of its interior cells.
18. Palindrome Sudoku. Shaded lines mark sequences of cells that must read identically from both directions, the same way a word spells the same forwards and backwards. On a six-cell palindrome line, the first and sixth cells match, the second and fifth match, and the third and fourth match, creating three pairs of locked values across the line.

Variants With Sequence and Pattern Rules

These six variants impose rules about the relationships between neighbouring or patterned cells rather than drawing explicit lines or requiring sums to be calculated.

19. Consecutive Sudoku. White bars between adjacent cells signal that those two digits differ by exactly 1, meaning they are immediate neighbours on the number line. Cells without a bar between them must not be consecutive, making absence just as meaningful as presence across the entire grid.
20. Non-Consecutive Sudoku. No two cells that share an edge anywhere in the grid may hold consecutive digits, with no exceptions. This single blanket rule restricts every cell from edge to centre and makes standard row-and-column scanning far less reliable than in any other variant on this list.
21. Even/Odd Sudoku. Some cells are shaded to mark them as holding only even digits, while others are marked as odd only. Knowing whether a cell is even or odd cuts its possible values from nine options to four or five immediately, and those reductions chain through adjacent regions quickly.
22. Skyscraper Sudoku. Clue numbers outside the grid indicate how many skyscrapers are visible from that edge, treating each digit as a building of that height and assuming taller buildings block shorter ones standing behind them. This turns the puzzle into a spatial reasoning challenge layered directly on top of a logic one.
23. Outside Sudoku. Digits placed in the margins indicate values that must appear within the first three cells of the corresponding row or column from that edge. The margin clue could occupy any of those three positions, keeping the exact location ambiguous while still narrowing the field of possibilities significantly.
24. Color Sudoku. Coloured regions are added on top of the standard box layout, with each colour acting as an independent no-repeat region across its cells. Some versions attach additional sum or positional rules to individual colours, turning each shade on the grid into its own mini constraint system running alongside everything else.

The Most Extreme Variants in the Set

These six variants pack in multiple rule layers simultaneously, often producing grids that need very few given digits to be fully solvable from start to finish.

25. Anti-Knight Sudoku. No two cells that are a chess knight's jump apart, meaning two squares in one direction and one square perpendicular, may share the same digit. The grid looks completely standard, but each digit now competes with cells spread far outside its row, column, and box, turning familiar scanning into a much wider search.
26. Anti-King Sudoku. Cells that touch diagonally, exactly the squares surrounding a chess king, cannot share the same digit. Combined with standard Sudoku rules, every interior cell is prevented from matching any of its eight immediate neighbours, which is a surprisingly powerful restriction that compounds across the entire grid.
27. Asterisk Sudoku. The nine cells forming a hidden asterisk shape in the centre of the grid act as an additional region and must each contain a different digit from 1 to 9. The asterisk cells are spread across the grid rather than grouped together, so identifying them and treating them as a tenth region is the essential first step.
28. Miracle Sudoku. This variant combines Anti-Knight, Anti-King, and Non-Consecutive rules all at once on the same grid. The combined restrictions are so severe that a valid Miracle puzzle can typically be solved in full from as few as two given digits, with no guessing or branching required at any point in the solve.
29. Quad Marks Sudoku. Small sets of digits are printed at the intersections of four cells, meaning each of those four cells must contain one of the listed values. Multiple quad marks spread across the grid interact with each other and quickly lock down placement options without any arithmetic calculation involved.
30. Battenburg Sudoku. A small checkered two-by-two marker appears at certain intersections to show that exactly two diagonally opposite cells among the four are even and two are odd. Where no marker appears, that checkerboard arrangement is explicitly forbidden, creating a dense network of odd-and-even logic that runs across the whole grid.

The Grid Never Runs Out of Room to Grow

Thirty entries is a long list, yet puzzle designers keep adding to it. New variants appear in online competitions every year, often combining two or three existing rule sets into something entirely original. A setter might pair Thermometer rules with Anti-Knight constraints, or run a German Whispers line directly through a Killer cage, and the result demands techniques from every active rule at once.

What all 30 entries above share is a respect for the original structure. Each variant keeps the fundamental promise of the game: nine digits, nine rows, nine columns, nine boxes, no repeats anywhere. Every extra rule builds on top of that foundation rather than replacing it. That is precisely what keeps variant Sudoku growing year after year. The base game is a perfect frame, and it turns out there is no shortage of interesting things to hang on it.