Nonogram terms, defined

Nonograms have their own small vocabulary — runs, gaps, overlap, forcing, and more. Knowing the words makes solving guides far easier to follow. The terms below are listed alphabetically. If you are brand new, start with the beginner's guide; once the basics click, the solving techniques page puts these ideas to work.

Cell

A single square in the grid. Every cell ends up in one of two states: filled (part of the hidden picture) or empty. There is no third option — a finished nonogram has every cell decided.

Clue

The number or numbers printed beside a row or above a column. Each clue lists the lengths of the filled runs 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.

Run / Block

A group of consecutive filled cells, with no empty cell breaking it up. Each number in a clue corresponds to exactly one run. The terms run and block are used interchangeably.

Gap

The empty cell or cells that separate two runs. There is always at least one gap between consecutive runs — that is why a clue of 1 1 in a three-wide line forces the pattern filled-empty-filled.

Line

A single row or a single column. Most nonogram reasoning happens one line at a time, since each line carries its own self-contained clue.

Line-solvable

A puzzle that can be solved by looking at one line at a time, never needing to guess and backtrack. Every puzzle on this site is guaranteed line-solvable, so a careful solver always reaches the answer through pure logic. See the beginner's guide for how to apply this in practice.

Overlap

The forced-middle technique. When a run is long relative to its line, its leftmost and rightmost possible positions share some cells in the middle — those overlapping cells must be filled. In a ten-wide line, a clue of 8 guarantees the middle six cells. It is usually the first move on a fresh grid.

Edge logic / anchoring

Reasoning that starts from the edge of a line. If the first cell of a row is already filled, the line's first run is anchored to that edge, so you can place the whole run immediately. Crosses and grid borders both act as anchors.

Forcing

Concluding that a cell must be filled or mustbe empty because every other arrangement consistent with the clue would break a rule. Forcing is the engine behind every deduction — overlap and edge logic are just common patterns of forcing.

Contradiction

A situation where a tentative assumption makes a clue impossible to satisfy. Spotting a contradiction lets you rule the assumption out and mark the opposite. On a well-made line-solvable puzzle you rarely need this, but it can unstick a tricky line.

Crossing off / marking

Placing an X (or a dot) on a cell you have proven empty. Marking known-empty cells is just as valuable as filling cells: an X blocks runs from being placed where they cannot go, which often unlocks the next deduction.

Validated / locked line

A line whose runs are all correctly placed and whose remaining cells are confirmed empty. On this site a validated line is locked — its clues turn green and it no longer needs your attention, so you can focus on the unsolved lines.

Nonogram

The general, trademark-free term for these picture logic puzzles. You fill cells according to the row and column clues to reveal a hidden image. It is the name used throughout this site.

Picross

A popular alternate name, short for “picture crossword.” Note that Picross is a trademark of Nintendo, whose handheld puzzle games made the name famous. The puzzles themselves are identical to nonograms.

Griddlers

Another name for nonograms, common in puzzle magazines and apps. Some griddler collections add color, where each clue number is tinted to show which color that run should be.

Hanjie

The name used for nonograms in many British newspapers and puzzle books. Same rules, same grids — only the label differs.

Pic-a-Pix

A branded name for nonograms used by Conceptis and others. Like griddlers, Pic-a-Pix puzzles often come in color as well as black and white.