Nonogram rules
A nonogram is a grid you fill in using number clues, and when it's done a picture appears. There's no arithmetic and no vocabulary — just a few simple rules about what the numbers mean. This page covers those rules and walks through one small puzzle from clues to finished picture. If you already know the rules and want solving technique, the step-by-step solving guide goes further.
The grid and the numbers
Every nonogram is a rectangular grid of squares. Along the top, each column has a list of numbers above it; down the left side, each row has a list of numbers beside it. Those numbers are the only clues you get — there is no partial picture to start from. Your job is to work out which squares should be filled in and which should be left blank, until every row and column agrees with its clue.
Each square ends up in one of two states: filled (part of the picture) or empty (background). Most players also put a small mark, like an ✕, in squares they've worked out must stay empty — that's not required by the rules, but it makes the puzzle far easier to read.
Rule 1 — each number is a run of filled squares
A single number tells you how many squares in that line are filled in one unbroken run. A clue of 5 on a five-wide row means the whole row is filled. A clue of 3 means exactly three squares in a row are filled somewhere along that line, and the other two are empty — you just may not know yet where the run sits.
Rule 2 — several numbers mean several runs, in order
When a clue has more than one number, each number is a separate run, and they appear in the same order as they're listed. A row clue of 1 1 means two single filled squares, the first one to the left of the second. A clue of 2 1 means a run of two, then later a run of one, in that order — never the one before the two.
The crucial extra rule: runs from the same clue must be separated by at least one empty square. Without that gap they'd just be one longer run. So on a five-wide row, the clue 1 1 could be placed a few different ways (filled-empty-filled-empty-empty, or filled-empty-empty-filled-empty, and so on), but the two filled squares can never touch.
Rule 3 — rows and columns must both be satisfied
A square isn't governed by its row clue alone — it has to satisfy its column clue at the same time. This is where the actual solving happens: a square is filled only if both the row and the column it belongs to require it. Cross-checking the two is how you turn "this run could go in a few places" into "this run must go exactly here."
Rule 4 — a proper nonogram has exactly one solution
A well-made nonogram can be solved by logic alone and has only one correct answer. You should never have to guess: every filled or empty square follows from the clues you already have. If a puzzle seems to need a guess, either there's a deduction you haven't spotted yet — or the puzzle is faulty. On this site every puzzle is machine-checked for a single, guess-free solution before it's published.
A worked example
Here's a small 5×5 puzzle. On the left is the starting position — just the clues. On the right is the finished picture. Notice the top row's clue is 1 1: two separate filled squares with a gap between them (the two bumps of the heart), exactly as Rule 2 describes. Every other line follows from cross-checking rows against columns.
Reading it back confirms every clue: the top row is 1 1 (two lone squares), the next two rows are 5 (completely filled), then 3, then a single 1 at the bottom point — and each column matches its own clue too (2, 4, 4, 4, 2).