Nonogram solver
Type the clues of a nonogram, one row or column per line, and press Solve. The solver works the way a person does, one line at a time, with the same rules our daily nonograms are graded by. When line logic stalls, it searches and tells you whether the puzzle has one solution, several or none.
How to type the clues
One line per row, from the top, and one line per column, from the left. Separate the numbers of a line with spaces or commas: 3 1 2 is a block of 3, then 1, then 2, in that order. An empty line is 0 or -. The grid can be up to 40 by 40 cells, and its size is simply the number of lines you type. The example button loads a 15x15 Medium picture from our own bank.
What the answer means
- Solved by line logic alone. Every step followed from one row or column, so the puzzle has exactly one solution and never needs a guess. The solver also says how hard it would be on our scale: Easy needs only simple boxes and finished lines, Medium splits lines at crossed cells, Hard pins blocks with the filled cells already known, and Expert checks every arrangement of a line.
- One solution, but it needs a guess. Line logic stalls, and the search finds exactly one way to finish the grid. You can solve such a puzzle by trying a cell and following the consequences, which is what the search does.
- More than one solution. The clues fit at least two pictures; the last frame outlines the cells that differ. Printed puzzles that do this usually have a typo in a clue.
- No solution. No grid fits every clue; the message names the line where logic broke down.
How it works
The step list comes from the same line solver that grades our daily puzzles; each step names its technique and the cells it decides, and the slider replays them. When the rules stop, the search takes the first undecided cell, tries it filled and then empty, and after each guess applies full line analysis to every row and column, backing up when a line can no longer fit its clue. It stops at the second solution, or after 50,000 branches or 3 seconds, whichever comes first. Everything runs in your browser: the clues are not sent anywhere.
Why our own nonograms never need it
Every nonogram we publish is line-solvable: the steps alone finish it, and a separate program confirms that the picture is the only solution. How we make the puzzles explains both checks; the nonogram techniques page shows every rule the solver uses, with diagrams.