Sudoku Jigsaw Sudoku: Sudoku with Irregular Regions
Jigsaw Sudoku (also known as Irregular Sudoku, Nonomino Sudoku, or Squiggly Sudoku) is a popular variant of the classic number-placement puzzle. Like standard Sudoku, you must fill a 9×9 grid so that every row and column contains the digits 1–9 exactly once. The twist? Instead of nine neat 3×3 boxes, the grid is divided into nine irregularly shaped regions — like pieces of a jigsaw puzzle. Each region contains exactly 9 cells and must also hold the digits 1–9 without repetition.
Jigsaw Sudoku evolved from the global Sudoku boom of the mid-2000s. Puzzle designers replaced the 3×3 boxes with irregular nonomino regions, and the variant gained exposure through the World Puzzle Championship where it appears regularly as a competition round.
📋 Rules of Jigsaw Sudoku
- Row rule — Each of the nine rows must contain the digits 1–9 exactly once.
- Column rule — Each of the nine columns must contain the digits 1–9 exactly once.
- Region rule — The grid is divided into nine irregular jigsaw-shaped regions of 9 cells each (shown by colour and thick borders). Each region must contain the digits 1–9 exactly once.
- Given digits — Some cells start pre-filled. Use these as your starting clues.
Start by scanning regions that stretch across many rows or columns — they create powerful elimination opportunities that don't exist in standard Sudoku.
⭐ Difficulty Levels
- Easy — 40 given digits. Solvable with naked singles and hidden singles alone. Great for beginners.
- Medium — 33 givens. Requires cross-hatching and region-line interaction.
- Hard — 28 givens. Demands naked pairs, hidden pairs, and locked candidates.
- Expert — 25 givens. Needs advanced strategies like X-Wing, Swordfish, and multi-step deduction.
🧠 Essential Strategies
1. Naked & Hidden Singles
If only one digit can go in a cell (naked single) or only one cell in a unit can hold a digit (hidden single), fill it immediately. These resolve the majority of cells in easier puzzles.
2. Region-Line Interaction (Locked Candidates)
This is the signature strategy of Jigsaw Sudoku. When a digit within a region can only appear in cells that share the same row or column, that digit is "locked" to that line. You can eliminate it from all other cells in that row or column outside the region. Because regions are irregularly shaped, these patterns appear far more often than in standard Sudoku.
Long, snaking regions that stretch across many rows create unique constraints. A region occupying cells in five different rows means those five row slots are claimed, narrowing possibilities for remaining cells. Use each region's shape as a solving tool.
3. Cross-Hatching with Irregular Regions
Scan rows and columns to determine where a digit can go within each region. Since regions are not confined to a 3×3 area, a single row can intersect three, four, or more regions, creating powerful cross-hatching chains.
4. Naked Pairs & Triples
If two cells in a row, column, or region can only contain the same two digits, those digits are locked to those cells and can be eliminated from other cells in that unit.
🆚 Jigsaw Sudoku vs Other Puzzles
- vs Standard Sudoku — Same row and column rules, but the nine 3×3 boxes are replaced by nine irregular regions.
- vs Killer Sudoku — Killer adds cage sum clues and starts empty. Jigsaw uses pre-filled digits but changes region shapes.
- vs KenKen — KenKen uses arithmetic operations on variable-sized grids. Jigsaw is purely placement logic.
🎮 More Sudoku Variants
- Classic 9×9 Sudoku — The original number puzzle.
- 4×4 Sudoku — Mini grid, ideal for beginners.
- 6×6 Sudoku — Medium-sized grid.
- Killer Sudoku — Cage sums with no given digits.
🖨️ Printable Jigsaw Sudoku — Free PDF Downloads
Want to solve on paper? Download our free printable jigsaw sudoku PDFs with answer keys — featuring irregularly shaped regions for a fresh twist:
- Easy Jigsaw Sudoku PDF — Plenty of givens, perfect for your first jigsaw experience.
- Medium Jigsaw Sudoku PDF — Fewer clues for more cross-hatching logic.
- Hard Jigsaw Sudoku PDF — Minimal givens for a real irregular-region challenge.
- Expert Jigsaw Sudoku PDF — The toughest jigsaw puzzles for experienced solvers.
Browse all our printable jigsaw sudoku puzzles or explore the full printable sudoku collection.
Frequently Asked Questions
Jigsaw Sudoku replaces the nine standard 3×3 boxes with nine irregularly shaped regions. Each row, column, and jigsaw region must contain the digits 1–9 exactly once. Also known as Irregular Sudoku or Nonomino Sudoku.
It depends on the puzzle. The irregular regions remove familiar 3×3 patterns but also create new elimination opportunities. Most solvers find it a refreshing challenge.
Yes. Every puzzle generated here has a unique solution reachable through pure logic — no trial and error needed.
Yes, 100% free with no sign-up or paywall required.