In jigsaw sudoku (also sold as irregular or squiggly sudoku) the nine 3×3 boxes are replaced by nine irregular regions of nine cells each. This jigsaw sudoku solver lets you redraw those regions on the grid in a minute, then solves the puzzle and explains each step.
How to draw the regions
- Choose Regions above the grid. The grid starts with the normal boxes, each in its own color.
- Pick a region number from the row of colored buttons, then tap or drag over the cells that belong to it. The small number under each button counts its cells.
- Repeat until every region matches your puzzle and each counter shows 9. Thick lines appear between regions as you paint.
- Switch back to Digits, type the clues, and press Solve or Next hint.
A line under the grid tells you if a region has too many or too few cells, so you can fix it before solving.
How the solver handles irregular regions
Each region is a unit, just like a box: it must hold 1 to 9 once. Hidden singles, naked and hidden subsets, and fish work exactly as in a classic sudoku. Intersections become more interesting: an irregular region can overlap a row in two, three or more cells, and the solver uses every overlap. If all the places for a digit in a region lie in one row, that digit is removed from the rest of the row, and the reverse.
Uniqueness techniques are not used on irregular layouts. If logic runs out, the solver falls back on a trial step and says so. Every step of every jigsaw puzzle in our tests (random irregular regions) matched the true solution.
A worked example
Load the example to see an irregular layout already drawn. The first hints are hidden singles inside the twisted regions; several steps later the solver needs an intersection between a region and a row, and the puzzle is rated Hard.
Tips
- Paint the oddest-shaped regions first; the last region usually fills itself in.
- Use Copy link to this puzzle to keep the regions you drew; the text box only stores the digits.
Want new region shapes to play? Jigsaw sudoku online generates a fresh irregular grid at three levels.
Solver tested . Found a problem? Tell us.
Questions
What is jigsaw sudoku?
A sudoku where the 3×3 boxes are replaced by irregular regions of nine connected cells. Rows, columns and regions must each contain 1 to 9 once.
Do the regions have to be connected?
In published puzzles they always are. The solver only needs each region to have exactly nine cells, so it also handles unusual layouts.
Why can my jigsaw puzzle not be pasted with its regions?
There is no common text format for regions, so you paint them on the grid. The share link saves both the regions and the digits.
Is jigsaw sudoku harder than classic sudoku?
Often a little, because the irregular regions make patterns harder to spot by eye. The solver rates each puzzle by the hardest technique it needs.