🖼️ How to solve nonograms step by step

In summary: Nonograms are solved by combining the numeric clues for each row with those for each column: you first shade in the cells that are guaranteed to overlap across every possible position of a block, then mark with an X the cells that get ruled out.

By Miguel Arechaga

Nonograms (also called picross, hanjie or griddlers) are puzzles where you paint cells following the numbers on rows and columns... and a picture appears at the end. They look like magic, but they are solved with pure logic. Here is the method from scratch.

What the numbers mean

Each number indicates a consecutive block of painted cells in that row or column. If a 10-cell row says “4 3”, there is a block of 4 painted cells, then at least one gap, then a block of 3. The order of the numbers is the order of the blocks.

The star technique: overlap

It solves 70% of the puzzle. Imagine that 10-cell row with “7”: the block of 7 can start at the earliest in cell 1 (covering 1-7) or at the latest in cell 4 (covering 4-10). In both extremes, cells 4, 5, 6 and 7 are painted for sure: paint them now. Quick rule: if the number is greater than half the row, there is guaranteed overlap in the middle.

X marks are worth as much as paint

Mark with an X every cell you know is empty. It is not optional: X marks shorten the rows and make the next overlaps bigger. Clear cases: when a block is complete, put X on both sides; when a gap is smaller than the smallest pending block, the whole gap is X.

The row-column loop

Every cell you solve in a row is new information for its column, and vice versa. The method is a loop: sweep all rows applying overlap and X, then all columns, then start again. Each pass unlocks more than the previous one; nonograms solve in cascade.

Sacred rule: never guess

A well-made nonogram never requires guessing. If you feel stuck and tempted to try your luck, stop: there is a deduction you are not seeing (check the edges, where it usually hides). Guessing in a nonogram ends in a corrupted picture ten moves later, with no idea where you went wrong.

Final tips

Start with rows holding big numbers or many numbers: they give the most information.
Board edges resolve first: a block against the edge has no room for doubt.
Start with 5×5 and 10×10 boards before jumping to the big ones.

📘 Keep reading: ️ How to play Nonogram or Picross (guide).

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