How to Solve Nonograms (Picross)
Nonograms — also known as Picross or Griddlers — are logic puzzles where you fill cells on a grid to reveal a hidden picture. Each row and column has a set of clue numbers listing the lengths of the filled blocks in that line, in order. A clue of "4 2" means a run of four filled cells, then at least one gap, then a run of two, reading left to right (or top to bottom). Your job is pure deduction: work out which cells are filled and which are blank, using only the numbers. A good nonogram always has one solution and never needs a guess.
The objective
- Fill cells so every row and column matches its clues exactly.
- Mark cells you've proven are blank so they don't confuse you.
- Reveal the hidden picture when the whole grid is correct.
Start with the biggest clues
Long clues constrain a line the most, so they're where certainty lives.
- Find lines where the clue nearly fills the length. In a 10-wide row, a clue of 8 leaves only two positions — and the middle six cells are filled no matter which position is correct.
- This is the overlap technique: slide the block to its leftmost and rightmost legal positions; any cell filled in both is definitely filled.
- Do this for every long clue, across rows and columns, before anything else.
Use the edges
Clues that touch the wall of the grid are easy wins.
- If a line starts with a clue and the first cell is filled, count out the full run from that edge immediately.
- When you know a run must begin at the edge, fill it and mark the cell right after it as blank.
- Corners often chain: filling an edge run in a row tells you cells in the crossing columns.
Mark the blanks
Blank cells carry as much information as filled ones — track them deliberately.
- When a clue is complete, mark the cells on either side of it as blank; runs must be separated by at least one gap.
- Forcing: if the only way to fit a clue leaves certain cells impossible to fill, mark them blank. Those blanks then constrain the crossing line.
- Cross-reference constantly: a filled cell you deduced in a row is a new clue for its column, and vice versa.
Solving habits
- Work one line at a time, fully, before moving on — squeeze every deduction out of it.
- Re-scan a line whenever a crossing line adds a filled or blank cell. New information often unlocks a stalled line.
- Never guess. If you're stuck, there's always another line with a forced move — find it.
- Use the picture as a sanity check, but solve by logic, not by guessing what the image "should" look like.
The payoff is that satisfying moment when scattered marks resolve into a recognisable image, and you got there entirely by reasoning.
Play Nonogram free and start with the longest clues. If you love deduction, Sudoku and Hashi — Bridges are excellent companions.
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