How to Play Nonogram (Picross): Beginner to Advanced Strategies
What is nonogram?
Nonogram (also called picross, hanjie, griddler, or paint-by-numbers) is a logic puzzle where a grid of cells is filled in based on numerical clues at the edges of rows and columns. Each clue tells you a run of consecutive filled cells. Multiple runs in the same line are separated by at least one empty cell. Solve the constraints and a small pixel-art image emerges.
Originally devised in 1987 by Japanese graphic editor Non Ishida (the source of the "nono" prefix), nonograms spread to international logic-puzzle magazines in the 1990s and to Nintendo handhelds as Mario's Picross in 1995. The format has surged in mobile app popularity in the 2020s.
Reading the clues
The clues at the start of each row and column are read left-to-right and top-to-bottom. Each number is a run of filled cells. Two adjacent runs in the same line are separated by at least one empty cell.
Example clue: 3 1 2. This means: a run of 3 filled cells, at least one empty, a run of 1 filled cell, at least one empty, then a run of 2 filled cells. The minimum line length to fit this is 3 + 1 + 1 + 1 + 2 = 8 cells. If the line is 8 cells, the placement is determined uniquely. If the line is longer, there is slack.
Edge logic (start here)
The fastest progress on any nonogram comes from lines whose clues fill the line completely or almost completely. A 10-cell row with clue 10 is trivially all filled. A 10-cell row with clue 5 4 needs minimum 5 + 1 + 4 = 10 cells — the entire line is determined. A 10-cell row with clue 5 3 needs minimum 9, leaving 1 cell of slack — meaning the central cells are guaranteed.
Always scan rows and columns for "minimum-equals-length" clues first. They unlock the most cells per second of thinking.
Overlap technique (the workhorse)
For any single-run clue n in a line of length L, slide the run to the leftmost position, then to the rightmost position. Any cells that overlap in both positions are guaranteed filled.
Example: line of 10 cells, clue 7. Leftmost placement: cells 1-7. Rightmost placement: cells 4-10. Overlap: cells 4-7 are guaranteed filled. That gives you four cells for free.
The overlap technique generalises to multi-run clues but the arithmetic gets fiddly. For most 5×5 to 15×15 puzzles, single-run overlap and edge logic combined will solve 60-80% of cells before you need anything harder.
Cross-out technique (just as important)
Filled cells get the spotlight, but proving cells are empty is half the game. The standard convention is to mark proven-empty cells with a small X (the cross-out). This visually shrinks the line and exposes more overlap opportunities.
Common cross-out triggers:
- A line with clue
0— every cell is empty. - A line entirely solved by overlap — cells outside the solved runs are empty.
- A row where intersecting columns have been determined empty.
Advanced patterns
For 15×15 and larger puzzles, you will eventually need techniques beyond pure single-line analysis.
Forcing
If filling a cell creates an impossible state elsewhere (a contradiction in another line), that cell must be empty. Conversely, if marking a cell empty creates a contradiction, it must be filled. Forcing is the bridge between pure deduction and trial-and-error.
Backtracking
Some puzzles, especially "deceptively hard" ones in expert collections, require a hypothetical mark followed by tracing the consequences. Many digital nonogram apps disallow backtracking and rely on solver-guaranteed unique solutions instead. If you find a puzzle that requires hypothetical reasoning, it is either flawed or intended to be expert-tier.
Pattern memory
After hundreds of puzzles, certain clue-set patterns become muscle memory. 1 3 1 in a 7-cell row is uniquely determined. 2 2 in a 5-cell row is uniquely determined. Building this library is the difference between a 4-minute and a 12-minute 15×15 solve.
Frequently Asked Questions
Is nonogram and picross the same thing?
Yes. "Picross" is a Nintendo trademark for nonogram-format games. "Hanjie" and "griddler" are alternative names used in puzzle publications.
Are all nonograms solvable by pure logic?
Well-posed puzzles, yes. The clues uniquely determine the solution. Apps and books that adhere to this convention are the standard.
What grid size should beginners start with?
5×5 to 10×10. The 5×5 mini on this site is a good starting point.
How long does a 15×15 puzzle take?
Beginner 30+ minutes. Intermediate 10-15 minutes. Expert under 5 minutes.