Jigsaw Sudoku

Jigsaw Sudoku. Boxes follow nine irregular regions, not the usual 3-by-3 grid.

How to play

Fill the 9×9 grid so every row, every column, and every 3×3 box contains the digits 1 to 9 with no repeats — the classic Sudoku rule. Jigsaw Sudoku adds one twist: Boxes follow nine irregular regions, not the usual 3-by-3 grid.

Jigsaw sudoku keeps the familiar goal — every row and column holds 1 to 9 with no repeats — but swaps the nine 3×3 boxes for nine irregular, interlocking regions, each of which must also contain a full 1 to 9. Because those regions bend across rows and columns in odd shapes, the no-repeat rule bites in places a classic grid never reaches, and reading the border geometry becomes half the puzzle.

How to solve Jigsaw Sudoku

The signature technique is the law of leftovers, a deduction that only exists because the regions are irregular: take a band of complete rows or columns — say the bottom two rows, which hold two full sets of 1 to 9 — and the jigsaw regions that lie almost wholly inside that band; the handful of cells where those regions poke out and the handful of band cells no whole region covers must contain an identical set of digits. Next, hunt hidden singles region by region, and watch for spillover — a region that swallows eight cells of one row forces that row's ninth digit into the single cell outside the region. Look for cells pinned by three constraints at once, since a long, thin region crossing a nearly complete row and column often leaves just one candidate where all three overlap. The bent shapes also throw up far more locked candidates than a 3×3 grid: when a region's only remaining slots for a digit all fall in one row or column, that digit clears out of the rest of that line. Read the region outlines before placing anything — short, fat regions behave much like ordinary boxes, while the long, snaking ones spanning only two or three rows are where the leftovers and locked-candidate wins hide.

Every Jigsaw Sudoku puzzle is free to play in your browser — no ads, no sign-up, and it works offline.

Frequently asked questions

What is Jigsaw Sudoku?

Jigsaw Sudoku (also called Irregular or Squiggly Sudoku) is a variant where the nine 3×3 boxes are replaced by nine irregular, interlocking regions of nine cells each, marked out by thicker borders. Rows and columns still hold 1 to 9 with no repeats, and every jigsaw region must hold 1 to 9 as well — so the puzzle plays the same but the misshapen regions create sharper deductions across rows and columns.

What are the rules of Jigsaw Sudoku?

Each row contains 1 to 9 with no repeats, each column contains 1 to 9 with no repeats, and each of the nine irregular regions contains 1 to 9 with no repeats. There are no 3×3 boxes — the regions are connected, jigsaw-like shapes instead — and as with classic Sudoku a valid puzzle has exactly one solution.

What is the law of leftovers in Jigsaw Sudoku?

It compares a set of full rows (or columns) with a set of whole jigsaw regions. Both cover the same number of complete 1-to-9 sets, so once you subtract the cells they share, the leftover cells sticking out of the regions and the leftover cells sticking out of the rows must hold exactly the same digits. That equivalence often pins one or two digits very early, which is why it is the most powerful opening move unique to irregular regions.