How to Solve Nonograms Without Guessing

Read clues in order, leaving at least one empty cell between separate runs. On a five-cell line, a clue of 5 fills the whole line. Clues of 2 2 also fit exactly: fill cells 1–2 and 4–5, with an X in cell 3.

If a line has room to slide, compare its legal placements instead of choosing the one that looks most like a picture. The overlap example above proves a move even though the whole line is not solved.

An X means confirmed empty, not “I have not filled this yet.” If the only clue is 3 and cells 1–3 are already confirmed filled, cells 4–5 must be empty.

Mark separators around a run only when you know that run is complete. Two adjacent filled cells under a clue of 3 still need another filled cell; placing X marks on both sides would be a mistake.

After proving a fill or X, check the perpendicular line through that cell. Discard any placement that leaves a known filled cell empty or covers a known X. Mark only what the remaining placements agree on.

For example, in a five-cell column with the single clue 3, a confirmed filled cell at the top forces cells 1–3 filled and cells 4–5 empty. An interior filled cell alone may not pin down the run. Repeat this row-to-column check after each deduction.

Recheck completed lines, large clues with overlap, and lines narrowed by X marks. Check that separate runs have their required gap and that an earlier mark was actually proven. Do not use the emerging picture as evidence.

If these beginner techniques reveal nothing, a puzzle may need a more advanced deduction; being stuck does not by itself mean guessing is required. Some puzzles are ambiguous or inconsistent. Use an explained hint to understand the next step rather than filling a likely-looking cell.