🎮 How to Play
- Numbers above each column / left of each row tell you how many filled cells in that line.
- Left-click to fill a cell. Right-click to mark it as empty (X).
- Solve to reveal the hidden picture.
About this tool
Nonograms (also Picross, Hanjie, Griddlers): logic puzzles where you fill cells in a grid based on numerical clues for each row and column. Solving reveals a hidden picture. Classic Japanese puzzle.
What a nonogram is
A nonogram is a logic puzzle in which numeric clues along each row and column tell you how to fill a grid of cells, and the filled cells reveal a hidden picture. There is no arithmetic and no luck: every cell can be deduced from the clues alone. The puzzle is also known as Picross, Hanjie, Griddlers, and Paint by Numbers.
It is a pure deduction game in the same family as Sudoku, but instead of placing digits you decide whether each square is filled or blank. Solving one trains exactly the kind of constraint-based reasoning that makes Sudoku and logic grids satisfying, with a small piece of pixel art as the reward.
How the clues work
Each clue is a sequence of numbers giving the lengths of the filled blocks in that line, in order, separated by at least one empty cell.
Clue 5 one run of 5 filled cells Clue 3 1 a run of 3, a gap, then a run of 1 Clue 2 2 2 three runs of 2, each separated by gaps Rule total filled = sum of clue numbers Rule minimum line width = sum of clues + (gaps between them)
The minimum-width rule is the engine of most deductions. If a clue's numbers plus the forced single-cell gaps almost fill the whole line, the blocks barely move, and the cells they must cover in every arrangement can be filled with certainty.
Worked example: a clue of 8 in a 10-cell row
Suppose a row is 10 cells wide and its only clue is 8. You cannot yet place all eight, but the overlap technique fills several cells immediately.
- Push the block left: it covers cells 1 through 8.
- Push the block right: it covers cells 3 through 10.
- Find the overlap: cells 3 through 8 are covered in both positions.
- Fill with certainty: those 6 middle cells must be filled no matter where the block actually sits.
- Use the result: the filled cells now constrain the crossing columns, unlocking the next deductions.
Solving techniques at a glance
A handful of repeatable moves solve most puzzles without any guessing.
| Technique | What it does |
|---|---|
| Overlap | Fills the cells a long block must cover in every valid position |
| Edge logic | Anchors a block when a clue starts at or near a wall |
| Gap marking | Marks cells as empty (X) once a run is complete to constrain neighbours |
| Forcing | Uses an already filled cell to pin the only block that can reach it |
| Cross-referencing | Alternates between rows and columns as each fill narrows the other |
Common pitfalls
- Guessing instead of deducing. A well-made nonogram never needs a guess. If you are stuck, an overlooked X or overlap is usually hiding in another line.
- Forgetting the mandatory gaps. Separate clue numbers always have at least one empty cell between their blocks; ignoring that gap overfills the line.
- Not marking empty cells. Crossing out known-empty cells with an X is as important as filling, because it pins where the remaining blocks can go.
- Ignoring the columns. Beginners work the rows and forget that every fill also constrains a column. Alternate constantly between the two.
- Miscounting long runs. On wide grids it is easy to be off by one. Count from a marked boundary rather than from memory.
- Starting with the small clues. Tiny clues leave the most freedom. Tackle the largest clues first, where the overlap technique pays off.
Related tools
Frequently asked questions
What do the numbers on a nonogram mean?
Each number is the length of an unbroken run of filled cells in that row or column, in order. A clue of 3 1 means a block of three filled cells, then at least one gap, then a single filled cell, reading left to right or top to bottom.
How do I start solving a nonogram?
Begin with the largest clues relative to the grid size, because they leave the least freedom. Use the overlap technique: slide a block to its far-left and far-right positions, and any cell filled in both extremes is definitely filled. Then mark cells you know are empty with an X to constrain the neighbours.
Does every nonogram have a unique solution?
A well-constructed puzzle has exactly one solution that can be reached by logic alone, with no guessing. Poorly made puzzles can have multiple solutions or require trial and error. The puzzles here are designed to be solvable by deduction.
What is the overlap technique?
For a single clue in a line, imagine the block pushed fully to one end, then fully to the other. The cells covered in both positions must be filled no matter how the block sits. For a clue of 8 in a 10-cell row, the middle 6 cells overlap and can be filled immediately.
What are nonograms also called?
They go by many names: Picross, Hanjie, Griddlers, Pic-a-Pix, Paint by Numbers, and Japanese crosswords. They were popularised in Japan in the late 1980s and the name nonogram comes from Non Ishida, one of the people credited with inventing them.