Sudoku Variants Explained: Eight Types and Their Rules
By Michel ·
Sudoku a Day Blog
Variants change the rules, grid size or regions of standard Sudoku. Here are eight formats and what to check before solving. Difficulty depends on the individual puzzle, not just the variant name.
Quick answer: choose by the rule you want to explore. Mini Sudoku uses a smaller grid, Diagonal adds two no-repeat units, and Thermo adds increasing sequences. Visit the Sudoku variants guide for illustrated rules or see the Thermo Sudoku example.
1. Killer Sudoku — Cage Sums
Killer Sudoku adds outlined cages to standard row, column and box rules. Digits in a cage add up to its given total and do not repeat within that cage. Some puzzles also include given digits; follow the stated rules.
Cage sums give you another way to restrict candidates. → Killer Sudoku rules and combinations
2. Diagonal Sudoku (X-Sudoku) — Two Extra Units
Diagonal Sudoku follows all standard rules plus one extra: the two main diagonals must also contain 1–9 without repeating. That gives 29 no-repeat units: nine rows, nine columns, nine boxes and two main diagonals.
The center cell belongs to both diagonals. → Diagonal Sudoku rules and example
3. Samurai Sudoku — Five Connected Grids
Samurai Sudoku is five overlapping 9×9 grids arranged in a cross pattern. Each grid follows standard rules, but the overlapping regions must satisfy both grids simultaneously. The usual arrangement has 369 distinct cells: five grids of 81 cells, with four nine-cell overlaps counted only once.
A shared cell must obey both grids it belongs to. → Samurai Sudoku rules and example
4. Jigsaw Sudoku — Irregular Regions
Jigsaw Sudoku replaces the standard 3×3 boxes with irregularly shaped regions. Each outlined region has nine cells and contains 1–9 once. Region shapes can vary; ordinary 3×3 boxes do not apply unless the puzzle explicitly requires both.
Follow the region outlines carefully, especially where they cross the usual box boundaries.
5. Hyper Sudoku — Four Extra Boxes
Hyper Sudoku adds four extra 3×3 boxes to the standard grid, positioned so they don't align with the normal boxes. That gives 31 no-repeat units: the usual nine rows, nine columns and nine boxes, plus four marked extra boxes. More constraints do not guarantee an easier puzzle.
Also known as Windoku or NRC Sudoku.
6. Mini Sudoku — Smaller Grids
Mini Sudoku uses a smaller grid, such as 4×4 with digits 1–4 and 2×2 boxes, or 6×6 with digits 1–6 and marked six-cell boxes. Check the digit range and box shape before starting.
7. Mega Sudoku — Larger Symbol Sets
A 16×16 Sudoku commonly uses 4×4 boxes and 16 distinct symbols. One symbol set is 1–9 plus A–G; other puzzles use different labels. Each row, column and box must contain every allowed symbol once.
Read the symbol key first. A larger grid changes the bookkeeping, but the no-repeat principle remains the same.
8. Thermometer Sudoku — Increasing Digits
Thermometer Sudoku adds thermometer shapes to the grid. Digits must strictly increase from the bulb to the tip. The thermometers give immediate ordering information that creates clean, satisfying deductions.
Increasing does not mean consecutive: 1, 3, 6 and 8 can form an increasing sequence. → Thermo Sudoku rules and example
Where to Start
There is no required order. Choose a rule that interests you and start with a puzzle intended for newcomers to that format. Read its own instructions, especially when it combines variants.
Standard Sudoku strategies provide useful candidate reasoning, but apply each technique only when the variant preserves the units and assumptions it needs.
→ See the Sudoku Variants guide for the available illustrated lessons. Our daily player and printable packs use standard Sudoku rules; these articles do not provide playable variants.