Nonogram Solver
Solve any nonogram, picross, or griddler from its clues. Type the row numbers and column numbers exactly as printed on the puzzle, click Solve, and the finished black-and-white picture appears — using the same line-solving logic human solvers use, automated to a fixpoint. Handles grids up to 25×25, entirely in your browser.
Numbers separated by spaces or commas. Enter 0 for a completely empty row or column. Blank lines are ignored.
Enter clues and click Solve — or load the worked example.
What Is a Nonogram?
A nonogram — also sold as Picross, Griddlers, Hanjie, Paint by Numbers, or Pic-a-Pix — is a grid puzzle where numbers beside each row and above each column tell you the lengths of the runs of filled cells in that line, in order, with at least one empty cell between runs. Fill the right cells and a pixel-art picture emerges. The clues alone determine the whole image; this solver reconstructs it from nothing but the numbers.
How Line-Solving Logic Works
The core human technique is overlap. Take a 10-cell row with the single clue 7. Push the block as far left as it can go, then as far right, and compare:
leftmost : ■■■■■■■□□□
rightmost : □□□■■■■■■■
overlap : □□□■■■■□□□
Cells 4–7 are filled in bothextremes, so they are filled in every legal placement — you can mark them immediately, before knowing anything else. The solver generalizes this: for each row and column it considers every placement of the clue blocks consistent with the cells already decided, and locks in any cell that takes the same value in all of them (including cells that must be empty).
Each deduction in a row narrows the possibilities in the columns crossing it, so the solver keeps cycling through changed lines until nothing new can be inferred. That fixpoint cracks almost every published puzzle. If cells remain undecided, it makes a guess on one cell, propagates, and backtracks on contradiction — a depth-limited search that settles the rare puzzles pure logic leaves open.
Worked Example: a 10×10 Heart
Click Worked example above to load a real 10×10 puzzle. Row 1 is 2 2 (the two bumps), rows 3–5 are 10(the full width of the heart), and the rows below shrink — 8, 6, 4, 2 — to the point. The columns mirror it with runs of 4, 6, and 7. The solver deduces the full rows instantly, the crossing columns then fix the bumps and the taper, and the finished heart renders in black and white.
Frequently Asked Questions
How do I enter my nonogram’s clues?
Row clues in the first box, one row per line, top to bottom. Column clues in the second box, one column per line, left to right, reading each column’s numbers top to bottom. Separate numbers with spaces or commas, and use 0 for an empty line.
What size puzzles can the solver handle?
Up to 25×25, including non-square sizes like 10×15. Standard 5×5 through 20×20 puzzles solve in well under a second.
How does the solver actually work?
Automated line solving: for every row and column it intersects all legal block placements given the known cells, locks in forced cells, and repeats until stable — with a depth-limited guess-and-check search for puzzles that stall.
What does the contradiction message mean?
No picture satisfies the clues you entered, and the named row or column is where the impossibility first surfaced. It’s nearly always a typo, a missed clue line, or columns entered in the wrong order. The solver also checks that row and column totals agree before starting.
Will it solve puzzles that require guessing?
Yes — the backtracking search handles them. Only extremely hard or ambiguous clue sets can exceed the search budget, and the solver says so instead of returning a wrong picture.
What if my puzzle has more than one solution?
You get one valid picture. Proper nonograms have a unique solution, so multiple solutions usually indicate an error in the clues.
Is the solver free and private?
Yes. No signup, and all solving runs in your browser — the clues never leave your device.
Want to Make a Nonogram Instead?
This page solves nonograms from clues. To go the other way — turn a picture or pattern into a printable puzzle — use the free nonogram maker, which generates clues and an answer key ready for classrooms or KDP books.
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Not affiliated with Nintendo. Picross is a trademark of Nintendo. Griddlers and Hanjie are trademarks of their respective owners.
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