Sudoku Variants

Classic 9×9 Sudoku is only the starting point. Over the decades, puzzle designers have created many variants that keep the core idea — fill a grid using logic — while changing the shape, the rules, or the kind of deduction required. This page is a practical introduction to the most widely played variants, how their rules differ from classic Sudoku, and what to expect when you try one.

Sudoku365's daily archive focuses on classic 9×9 puzzles. If you want to try a variant, plenty of puzzle magazines and logic-puzzle communities publish them. The goal here is to help you recognise the names, understand the rules, and choose a variant that suits the kind of challenge you want.

Killer Sudoku

Killer Sudoku combines the logic of Sudoku with the arithmetic of Kakuro. The 9×9 grid is divided into "cages" marked by dotted lines, and each cage has a small number showing the sum of the digits it contains.

Rules

• Standard Sudoku rules apply: no repeated digit in any row, column, or 3×3 box.
• The digits inside each cage must add up to the stated sum.
• A digit cannot repeat inside a single cage.

Killer Sudoku often starts with no given numbers at all — the cage sums are the only clues. Experienced solvers rely on "sum combinations" (for example, a 3-cell cage with sum 6 can only be 1+2+3) to crack open the opening moves.

Samurai Sudoku

Samurai Sudoku links five 9×9 grids in an X pattern. Four outer grids share a 3×3 corner box with a central grid, which means clues in one grid constrain another.

Features

• Five overlapping 9×9 grids, sharing four corner boxes.
• A total of 369 cells — much larger than a classic puzzle.
• Progress in one grid often unlocks progress in an adjacent grid.

Samurai puzzles reward patience. It helps to treat each grid as almost independent and look for moments where the shared boxes force a placement in the next grid.

Mini Sudoku (4×4)

Mini Sudoku uses a 4×4 grid split into four 2×2 boxes, with digits 1 to 4. It's often the first puzzle a child or new solver encounters.

Why start here

• Fast: A Mini puzzle can be solved in a minute or two.
• Introduces the core rules: The "no repeat" constraint applies to rows, columns, and boxes just like the full-size version.
• Low frustration: Every puzzle is short enough to finish in a single sitting.

6×6 Sudoku

A 6×6 grid with 2×3 boxes and digits 1 to 6. The rectangular box shape is interesting because it changes the usual scanning pattern — most solvers find they scan horizontally more than they would in a 9×9 puzzle.

6×6 Sudoku is a natural bridge between Mini and full-sized puzzles. It introduces slightly more complex deductions without becoming intimidating.

Hexadoku (16×16)

Hexadoku is a 16×16 puzzle using digits 0 to 9 and letters A to F — the sixteen hexadecimal digits — or sometimes simply the numbers 1 to 16. The grid is divided into sixteen 4×4 boxes.

What's different

• 256 cells instead of 81.
• Each row, column, and box must contain all sixteen symbols.
• Solving times of 30 minutes to several hours are normal, even for experienced players.

Because the grid is so large, pencil marks become essential. Most solvers cannot hold the state of a 16×16 puzzle in their head.

Sudoku X (Diagonal Sudoku)

Sudoku X adds one constraint to classic rules: the two main diagonals must also contain each digit exactly once. That small change forces more deductions early on, since eighteen extra cells are now under a uniqueness rule.

In practice, Sudoku X puzzles can have fewer given clues than classic puzzles while still having a unique solution, because the diagonals carry extra information.

Jigsaw Sudoku

Jigsaw Sudoku (sometimes called Irregular Sudoku) replaces the nine 3×3 boxes with nine irregularly shaped regions of nine cells each. Rows and columns still follow normal rules, but the "box" shapes are now jagged.

The solving feel is different from classic Sudoku: scanning is less helpful because the boxes do not line up neatly with rows and columns, so candidate elimination plays a bigger role.

Hyper Sudoku

Hyper Sudoku keeps the standard 3×3 boxes but adds four extra 3×3 "windows" that also must contain each digit once. The extra windows typically sit in the interior of the grid.

The extra constraints make openings much easier — the additional regions quickly eliminate candidates — but the puzzles tend to come with fewer given clues to compensate.

Why Try a Variant?

• A fresh feel: Classic Sudoku can start to feel routine once you've internalised the common techniques. Variants bring back the beginner's sense of discovery.
• New deduction patterns: Each variant emphasises different tactics — arithmetic combinations in Killer, cross-grid reasoning in Samurai, diagonal eliminations in Sudoku X.
• Deeper appreciation of the core rules: After playing a few variants, the simplicity of classic Sudoku feels elegant rather than limited.

Staying With Classic 9×9

If you'd rather stick with the classic format, Sudoku365's daily archive has four difficulty levels every day of 2026. Pair that with the strategy tutorials to work through progressively harder puzzles at your own pace.