Nonogram solver facts at a glance
The nonogram solver takes any black-and-white nonogram from 5x5 to 25x25, finds the picture, and checks whether it is the only one. It is free, needs no account and runs in your browser.
| Grid sizes | 5 to 25 rows and 5 to 25 columns, square or not; one tap for 5x5, 10x10, 15x15, 20x20 or 25x25 |
|---|---|
| Clue entry | One box per row and per column, or paste every clue at once as text |
| Input checks | Every clue must fit its line, and the row clues and column clues must add up to the same number of filled cells |
| Method | Line logic on every row and column, then trial and error with line logic after each try |
| Second answer | Searched for every time; if found, both pictures are shown with the cells that differ outlined |
| Time limit | 5 seconds per puzzle, in a background worker so the page stays responsive |
| Step replay | The grid after each line deduction, and how many cells line logic found versus trial and error |
| Share | Copy puzzle link reopens the clues and solves them; Copy picture as text uses # for filled and . for empty |
| Price and setup | Free, no account, no download; runs in your browser |
How to use the nonogram solver
Set the grid size, type the numbers of each row and each column exactly as your puzzle shows them, and press Solve: the finished picture appears in the grid, and Back, Next and Play replay how it was found.
- Set the grid size. Tap 5×5 up to 25×25, or choose any number of rows and columns from 5 to 25.
- Type the row clues. For each row, from the top, type its numbers left to right, such as
2 1 3. Leave the box empty for a row with no filled cells. - Type the column clues. For each column, from the left, type its numbers top to bottom. The grid shows your clues around its edges as you type, so you can compare it with your puzzle.
- Press Solve. If a clue cannot fit or the totals do not match, the page names the line to fix. Otherwise the picture appears, and the note says whether it is the only one.
- Replay and keep the answer. Next and Back show the grid after each row or column the logic worked on. Copy puzzle link saves a link that reopens your clues, and Copy picture as text gives the answer as rows of # and dots.
Picross, Griddlers, Hanjie: one puzzle, many names
Nonograms go by many names: Picross, Griddlers, Hanjie, paint by numbers and Japanese crosswords. The rules are the same. Each number beside a row or above a column is the length of one block of filled cells in that line, the numbers are in order, and there is at least one empty cell between two blocks. A row clue of 3 1 means a block of 3, a gap, then a single cell. When every line matches its clue, the filled cells form a picture.
This solver handles the classic black-and-white puzzle. Color nonograms, where blocks of different colors may touch, and triangle variants are not supported.
The overlap rule: how to start a nonogram by hand
Slide a block as far left as it can go, then as far right; the cells it covers both times must be filled. In a row of 10 with the clue 7, the block covers cells 1 to 7 or 4 to 10 at the extremes, so cells 4 to 7 are filled whatever happens. With the clue 3 4 in a row of 10, the blocks need 8 cells, leaving 2 spare: cell 3 belongs to the 3 for sure, and cells 7 and 8 to the 4. Start with the biggest clues, mark the cells you are sure are empty, and use each new cell as a hint for the line that crosses it.
Line logic is the full version of this rule: for one line, it considers every way the blocks can be placed that agrees with the cells already known, and keeps the cells that are filled in all of them or empty in all of them. Try the Heart and Mug examples: line logic alone finishes both. The Cat face example is harder: line logic finds 217 of its 225 cells, and the last 8 need trial and error.
How to solve a nonogram by hand, step by step
- Fill the easy lines first. A clue of 0 means the whole line is empty. A clue that fills the line once you add one gap between blocks, such as 3 1 4 in a row of 10, gives the whole line at once.
- Use the overlap rule on big clues. Any block longer than half its line has cells that are filled wherever it sits.
- Work from the edges. A filled cell in the first cell of a line must start the first block, so fill the rest of that block and mark the cell after it empty. The same goes for the last block at the other end.
- Mark empty cells. As soon as a line has all its blocks, cross out its other cells. Crosses are as useful as filled cells.
- Switch between rows and columns. Every new cell is a fresh hint for the line that crosses it. When nothing moves, pick a cell and ask whether filling it would break its row or column; if it would, it is empty.
The solver’s replay also works one line at a time: press Solve, then Next, and each step shows the grid after one row or column.
When a nonogram has two answers or none
A clue set can allow more than one picture. Load the Two answers example: two lone cells sit on one diagonal of a 2x2 square, and the other diagonal gives the same count in every row and column, so both pictures fit. The solver keeps searching after the first picture, shows the second one, and outlines the 4 cells that differ. It also catches clues that cannot work: the Heart with a typo example has one column clue changed from 4 to 2 2, and line logic runs into a contradiction in column 2.
How the solver works
The solver first checks the clues, then runs line logic until no row or column changes. For each line, a dynamic program over block positions finds every cell that is forced filled or forced empty; each line that changes wakes up the lines that cross it. If cells are still open, it probes them: it tries each open cell both ways, runs line logic again, and keeps a value whenever the other one leads to a contradiction. If that is still not enough, it guesses the cell whose two outcomes settle the most cells and backtracks on contradictions. It does not stop at the first picture; it looks for a second one to prove the answer is unique. The search runs in a background worker for at most 5 seconds.
Frequently asked questions
Which puzzles can the nonogram solver handle?
Any black-and-white nonogram from 5x5 to 25x25, square or not, with one clue for every row and every column. That covers puzzles sold as Picross, Griddlers, Hanjie, paint by numbers and Japanese crosswords. It does not solve color nonograms, where each block also has a color.
Why does it say more than one picture fits?
Some sets of clues allow two or more pictures. The simplest case is two lone cells on a diagonal of a 2x2 square: moving both to the other diagonal keeps every row and column count the same. The solver shows two pictures and outlines the cells where they differ. A puzzle from a good book or app has one answer, so check the clues of those rows and columns.
Why does it say no picture fits my clues?
Almost always a clue was copied wrong. Before solving, the page checks that every clue fits its line and that the row clues and the column clues add up to the same number of filled cells. If they pass but the clues still contradict each other, it names the line where the contradiction showed up and lets you replay the steps that led there.
Does the solver guess?
Only when it has to. It first uses line logic, the same reasoning you use by hand, and many puzzles are finished that way. If cells are still open, it tries a cell both ways, keeps the value that does not lead to a contradiction, and branches only if both work. The result says how many cells line logic found and how many needed trial and error.
Are Picross, Griddlers and Hanjie the same puzzle?
Yes. They are different names for the same rules: the numbers beside each row and above each column give the lengths of the filled blocks in that line, in order, with at least one empty cell between blocks. Nonogram is the general name.
Can I upload a screenshot or photo of my puzzle?
No. The solver works from typed clues only. To save typing on a big puzzle, use Paste all clues at once: one row clue per line, top to bottom, then a blank line, then one column clue per line, left to right.
How do I solve a nonogram by hand?
Start with the easy lines: leave every cell of a line with a 0 clue empty, and fill every cell of a line whose clue equals its length. Then use the overlap rule on long blocks, work in from the edges, cross out cells as soon as a line is complete, and keep switching between rows and columns. The replay above also works one row or column at a time.
Is the nonogram solver free?
Yes. It is free, with no account and no download, and it runs in your browser. A puzzle link keeps the clues in the link itself.