Jigsaw Sudoku

Jigsaw sudoku is a 9×9 number-placement puzzle where the familiar 3×3 boxes are replaced with nine irregularly shaped regions. You might know it by another name: squiggly sudoku is the second most common term, and some publishers call it irregular sudoku, nonomino sudoku, or geometric sudoku. They're all the same puzzle.

The row and column rules are unchanged from standard sudoku: fill every row and every column with the digits 1 through 9, each appearing once. The difference is the third constraint. Instead of checking a tidy 3×3 square, you have to track which digits go where inside a jagged, oddly shaped region that might span four rows, wrap around a corner, or zigzag across the grid.

Each region still has exactly 9 cells, and each region still needs all nine digits. But because the shapes vary from puzzle to puzzle, you can't rely on muscle memory. The box-scanning technique that carries you through most regular sudoku puzzles simply doesn't work here.

The rules are short:

1. Fill every cell with a digit from 1 to 9.
2. Each row contains 1–9 exactly once.
3. Each column contains 1–9 exactly once.
4. Each irregular region contains 1–9 exactly once.

That's it. If you know how to play regular sudoku, you already know the rules. The challenge comes from the irregular regions themselves. Our grid uses color-coded backgrounds and thick borders to mark region boundaries, so you can tell at a glance which cells belong together.

For a full walkthrough with solving strategies, check the jigsaw sudoku rules page.

We offer five difficulty tiers. Most competitors stop at three or four. The range matters because jigsaw sudoku gets interesting fast once you drop below 30 givens.

Easy (36–45 givens): Scanning and naked singles will get you through. Good starting point if you've never tried a jigsaw layout before.

Medium (30–35 givens): Hidden singles in irregular regions become necessary. You'll start noticing how region shapes affect which cells you can eliminate.

Hard (25–29 givens): Pair-based logic and the Law of Leftovers technique come into play. Region tracing is no longer optional.

Expert (22–24 givens): Pointing pairs, X-Wings, and chain techniques across irregular boundaries. Significantly harder than expert standard sudoku because the regions don't align to neat rows.

Einstein (24–28 givens): Every puzzle is certified solvable through logic alone, with no guessing or bifurcation. The irregular regions make this substantially harder than Einstein-level standard sudoku. Nobody else offers this difficulty for jigsaw sudoku.

This is the technique that separates jigsaw sudoku from regular sudoku. It doesn't exist in standard puzzles because it depends on irregular region shapes.

Here's how it works: when an irregular region mostly fits inside a band of rows (say rows 1–3), some of its cells will spill into rows outside that band, and cells from other regions will spill in. The digits in the cells that spill out must be the same as the digits in the cells that spill in. This gives you concrete information about specific cells that you can't get from row, column, or region elimination alone.

The full walkthrough with diagrams is on our rules and strategy page. It's the single most useful technique for hard puzzles and above.

The short answer: jigsaw sudoku is harder for most people.

In regular sudoku, the 3×3 boxes are fixed. After solving a few hundred puzzles, your brain learns to scan boxes automatically. You don't think about where a box starts and ends because every puzzle uses the same layout.

In jigsaw sudoku, the regions change shape every time. A region might cover cells from five different rows, or wrap around the center of the grid in an L-shape. You have to actively trace the region boundary for every elimination step, which is slower and more error-prone. The trade-off is that jigsaw sudoku stays interesting longer. It's harder to autopilot through a puzzle when the layout keeps changing.