Every sudoku variant explained: the complete list

The baseline: classic 9×9

Nine rows, nine columns, nine 3×3 boxes; place 1–9 so no row, column or box repeats a digit. Every variant below is a deliberate mutation of this puzzle, so if you're new, start here — every solving technique you learn on the classic grid transfers to everything else on this page.

In Sudoku by Joseph: yes, free, with difficulties from Easy to Diabolic.

Size variants: same rules, different scale

6×6 Mini Sudoku

A six-by-six grid using digits 1–6, with 2×3 rectangular boxes instead of squares. The logic is identical to classic sudoku but the search space is tiny, so puzzles resolve in a few minutes. It's the standard on-ramp for kids and the format many newspapers run beside the main puzzle.

Why play it: the fastest way to teach the row/column/box interaction without overwhelming a beginner.

In Sudoku by Joseph: no — described here for completeness. The app's twelve variants start at 9×9.

16×16 Sudoku (Hexadoku / Super Sudoku)

Sixteen rows and columns, 4×4 boxes, and sixteen symbols — usually 0–9 plus A–F, which is why electronics magazines dubbed it Hexadoku. No new logic is required, but the bookkeeping explodes: 256 cells, sixteen candidates each, and pencil marks stop being optional. A single puzzle is comfortably an evening.

Why play it: endurance sudoku. If classic Diabolic puzzles fall in twenty minutes, this is the next wall. Full guide: how to play 16×16 sudoku.

In Sudoku by Joseph: yes, premium.

Region variants: redraw the boxes

Jigsaw Sudoku (irregular / squiggly / nonomino)

The nine 3×3 boxes are replaced by nine irregular, interlocking regions of nine cells each — the "jigsaw pieces" that give the variant its name. Rows and columns work as always, but the region shapes break your spatial habits: the box-scanning reflexes you've built on classic grids point you at the wrong cells.

Why play it: it makes region logic conscious again. The Law of Leftovers — comparing what a region and a set of rows must contain — is a genuinely new technique that only exists here. Full guide: how to play Jigsaw sudoku.

In Sudoku by Joseph: yes, free.

Windoku (Hyper Sudoku / NRC Sudoku)

A classic 9×9 grid with four extra shaded 3×3 regions floating inside it, arranged like window panes — each shaded square must also contain 1–9 exactly once. The four extra constraints overlap the normal boxes, which produces surprisingly dense deductions from very few givens.

Why play it: maximum constraint density on a normal-sized grid; popular in Dutch newspapers (hence "NRC Sudoku").

In Sudoku by Joseph: no. Windoku is not one of the app's twelve variants — it's listed here because no variant survey is complete without it.

Arithmetic variants: numbers that add up

Killer Sudoku (sumdoku)

No givens at all. Instead, the grid is divided into dotted "cages," each labeled with the sum of the digits inside it — and digits can't repeat within a cage. All normal sudoku rules still apply. The opening moves come from arithmetic: a two-cell cage summing to 3 must be 1+2; a cage summing to 45 covering a full row tells you what the leftover cell outside it holds (the famous 45 rule).

Why play it: it's the most popular variant in the world for a reason — the blend of light arithmetic and pure logic gives it a completely different rhythm from classic sudoku, and the difficulty ceiling is enormous. Full guide: how to play Killer sudoku.

In Sudoku by Joseph: yes, free.

Adjacent: Kakuro

Worth one paragraph of disambiguation because searchers conflate them: Kakuro is a crossword-shaped grid where runs of cells must hit a target sum with no repeated digits. It shares Killer's sum-combination arithmetic but drops the sudoku grid entirely — no rows-columns-regions structure. If you enjoy the cage math in Killer, Kakuro is the neighboring puzzle; it just isn't sudoku, and it isn't in the app.

The multi-grid family: Gattai and overlapping sudoku

This is the family most lists get wrong or skip entirely. The Japanese term is gattai (合体, "merged"): two or more complete 9×9 grids are printed overlapping, sharing one or more 3×3 boxes. A digit placed in a shared box must be valid in every grid that box belongs to — that's the entire trick, and it's what makes these puzzles feel like solving several sudokus that keep passing notes to each other. Gattai-N simply means N overlapping grids, so the famous Samurai layout is formally Gattai-5.

All eight multi-grid variants below are in Sudoku by Joseph as premium variants — to our knowledge the widest overlapping-sudoku lineup in any single app (see the honest multi-grid app comparison).

Twodoku (Gattai-2)

Two overlapping grids — the gentlest introduction to the family. You solve two puzzles that share territory, and information flows both ways across the shared region.

Why play it: learn the overlap mechanic without committing to a poster-sized puzzle.

Tripledoku

Three interlocking grids in a stepped chain. The middle grid touches both neighbors, so it becomes the information hub of the puzzle — progress there unlocks both ends.

Why play it: the first layout where you must consciously route deductions through a grid rather than just across one border.

Gattai-3

Three grids sharing regions in the classic merged arrangement. Functionally Tripledoku's sibling; the overlap geometry differs, and with it which boxes carry double duty.

Why play it: the standard "medium" of the family — a real multi-grid solve in one sitting. Rules in detail: the rare multi-grid family explained.

Kazaguruma (Windmill Sudoku)

Five grids — four arranged like the blades of a pinwheel around a central grid (kazaguruma is Japanese for windmill), overlapping in rotational symmetry. The blades all play the same structural role, which leaves no obvious corner to anchor on.

Why play it: the rotational layout forces you to keep several solving fronts open at once. Full rules: Windmill, Sohei, Flower & Gattai.

Sohei

Four grids arranged in a cross — named for the warrior monks of feudal Japan — with a hole in the middle: unlike Samurai, there is no central grid. Each grid overlaps its two neighbors, forming a ring of dependencies with no center to pivot from.

Why play it: the ring structure is unique — deductions must travel the long way around.

Samurai Sudoku (Gattai-5)

The icon of the family: five overlapping grids, one in the center connected to four at the corners. The center grid shares a box with each neighbor, making it the crossroads of the whole puzzle. Newspapers popularized it as the "weekend killer" format.

Why play it: it's the flagship multi-grid experience, and the one with an actual solving literature. Full guide: how to play Samurai sudoku.

Cross Sudoku

A cross-shaped multi-grid arrangement — grids extending outward in the four compass directions. Reads like Samurai's leaner cousin: the same crossroads logic in a different silhouette.

Why play it: Samurai-style solving with different overlap geometry, which changes where the pressure points sit.

Flower Sudoku

Five grids in a tight flower-petal arrangement — the overlaps are larger than Samurai's corner-touch, so the grids share much more territory. More shared cells means more constraints, which typically makes Flower feel denser than Samurai despite the same grid count.

Why play it: the most tightly-coupled layout in the family; nearly every placement echoes somewhere else. (Note: this is the adult logic variant — not the "flower sudoku" picture puzzles printed for preschoolers.)

Honorable mentions: constraint variants

These classics change the rules on a single 9×9 grid rather than the geometry. None are in Sudoku by Joseph; they're listed so you can place the names.

• Diagonal Sudoku (X-Sudoku): both main diagonals must also contain 1–9 exactly once. Two extra "rows" that cross the whole grid — simple to state, meaningfully harder to solve.
• Consecutive Sudoku: a bar between two cells means their digits differ by exactly 1 — and crucially, no bar means they don't. The negative constraint does most of the work.
• Thermo Sudoku: thermometer shapes drawn on the grid; digits must strictly increase from the bulb along the tube. A staple of modern setting culture and puzzle-hunt communities (you'll see it constantly on competition sets and solving channels).

Which variant should you start with?

A practical path rather than a menu:

• New to sudoku: classic 9×9 on Easy until box-line scanning is automatic.
• Classic feels routine: Jigsaw first (same digits, broken habits), then Killer (new arithmetic layer). Both are in the free tier, so this far costs nothing.
• Want a project: 16×16 for endurance, or enter the multi-grid family through Twodoku and work up — Twodoku → Gattai-3 → Samurai is the natural staircase, and the multi-grid guide covers where to play each.
• Already a Samurai regular: Sohei, Flower and Kazaguruma are the layouts almost nobody ships — rules for all three here.

In Sudoku by Joseph the free download includes Classic, Jigsaw and Killer (ad-supported); premium removes the ads and unlocks the other nine variants, with a 7-day trial to find out whether multi-grid solving is your thing before paying anything.

Other options worth knowing

No single app covers everything on this page, ours included. Conceptis publishes polished, hand-made puzzles across many of these variants — its MultiSudoku app covers overlapping layouts through curated puzzle packs sold per volume, and it's a respected shop. samurai-sudoku.com offers free multi-grid solving in the browser. For constraint variants like Thermo, the apps from the Cracking the Cryptic team carry superb hand-set puzzles. Sudoku by Joseph's lane is breadth in one native mobile app: twelve variants, unlimited puzzles generated on-device, offline, in 46 languages — and no lives or coins in any of them.

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