Jigsaw Sudoku—also called Irregular Sudoku—uses nine outlined regions that bend around the grid. Each region contains nine cells and must hold digits 1–9 once, just like a classic 3×3 box.
How do you play Jigsaw Sudoku?
Fill the 9×9 grid so each row, column and irregular nine-cell region contains digits 1–9 exactly once. Trace region boundaries carefully, list missing digits inside each shape and use crossing rows and columns to restrict them. Classic singles, locked candidates and subsets still work, but region geometry changes where intersections occur.
What are the rules of Jigsaw Sudoku?
Rows and columns follow standard Sudoku rules. The difference is regional: regular 3×3 boxes disappear and nine irregular shapes take their place. Every outlined region contains nine cells and digits 1–9 once.
The shapes must not overlap, and every cell belongs to one region. Thick or colored borders normally mark the jigsaw edges. If a boundary is faint, trace it before adding candidates; assigning a cell to the wrong region corrupts every later deduction.
How should you read irregular regions?
Choose one shape and physically follow its outline around all nine cells. Mark its missing digits. Because a region may span many rows and columns, a single digit can be blocked by several distant givens rather than a neat pair of crossing lines.
Look for narrow arms and one-cell protrusions. A region occupying many cells in one row may reserve candidates there, while its remaining cells interact strongly with other rows. The strange shape is information, not decoration.
Which strategies work best in Jigsaw Sudoku?
Naked and hidden singles transfer unchanged. Locked candidates also transfer: if every candidate 3 in one irregular region lies on column 7, remove 3 from column 7 outside that region.
Subsets can be stronger because irregular regions create unusual overlaps. If three region cells in one row contain only {2,5,8}, those digits are reserved in both the region and the row. Search region-line intersections after every candidate update.
Do X-Wings still work?
Yes. X-Wing depends on rows and columns, which remain standard. Most line-based techniques transfer, while box-specific language should be reinterpreted as region-based logic.
Is Jigsaw Sudoku harder than classic Sudoku?
It feels harder at first because solvers cannot rely on familiar 3×3 scanning patterns. Once region boundaries become easy to read, the logic is recognizable and may even offer stronger intersections.
Jigsaw Sudoku is a good next variant for players who want classic candidate logic without arithmetic. It exposes which habits depend on rectangular boxes and which techniques truly depend only on units and overlap.
Our game / Story-led deduction
Want each placement to reveal part of a mystery?
Detective Sudoku is not classic Sudoku. It replaces digits and boxes with suspects, rooms and truthful spatial clues while retaining one suspect per row and column. Its real hints identify the clue behind a deduction instead of giving you the answer or solution.
See what makes Detective Sudoku different →Frequently asked questions about Jigsaw Sudoku
Is Jigsaw Sudoku the same as Irregular Sudoku?
Yes. Both names usually describe a 9×9 Sudoku using irregular nine-cell regions instead of 3×3 boxes.
Does each jigsaw region have nine cells?
In standard 9×9 Jigsaw Sudoku, yes. Each region contains digits 1–9 once.
Can classic Sudoku techniques solve Jigsaw Sudoku?
Most can. Replace box-based reasoning with irregular-region reasoning while keeping row and column techniques.
Does Jigsaw Sudoku use arithmetic?
No. Digits are placement symbols, just as in classic Sudoku.