What Do the Numbers Mean in a Web Paint-by-Number Puzzle?

In Web Paint-by-Number (also called nonograms or picross), the numbers on each row and column tell you the lengths of consecutive filled blocks in that line. A single number means one continuous run of filled cells. Multiple numbers mean multiple runs, in that exact order, with at least one empty cell between each run. The numbers never tell you where the runs start—only how long they are and in what sequence.

The Three Core Rules

1. One number = one continuous block

A row labeled "5" on a 10-wide grid means there is exactly one run of 5 filled cells somewhere in that row. The other 5 cells are empty. The run could sit at the far left, the far right, or anywhere between—the puzzle doesn't say yet.

2. Multiple numbers = multiple blocks with gaps

A row labeled "2 3" means: first a run of 2 filled cells, then at least one empty cell, then a run of 3 filled cells. The gap can be one cell or several—anything ≥1 satisfies the rule. The total filled cells in that row is 2 + 3 = 5, but the row must be at least 2 + 1 + 3 = 6 cells wide to fit.

3. Order matches reading direction

For rows, numbers read left to right. For columns, numbers read top to bottom. So "3 1" in a column means the 3-block is above the 1-block—never the reverse.

Worked Example

Take a 10-cell row with the clue "4 2":

• Cells 1–4: a run of 4 ✓
• Cell 5: empty gap ✓
• Cells 6–7: a run of 2 ✓
• Cells 8–10: empty (allowed—trailing empties are always fine)

This satisfies "4 2." So would shifting the whole pattern right by one cell, as long as everything still fits in 10 columns.

Minimum Space and Overlap

A useful mental shortcut: the minimum width a clue needs is the sum of its numbers plus one empty cell between each pair. For "4 2" that's 4 + 1 + 2 = 7. On a 10-wide row you have 3 cells of "slack" to distribute as extra empties before, between, or after the blocks.

When slack is small, blocks are forced into overlapping positions—and overlapping cells are guaranteed filled. For example, a clue of "6" in a 10-wide row: the block can start anywhere from position 1 to position 5. Positions 5 and 6 fall inside every possible placement, so those two cells must be filled. This "overlap trick" is the fastest way to make your first marks.

Common Points of Confusion

• "Does '1 1' mean two adjacent cells?" No. Two separate 1s require at least one empty cell between them, so "1 1" needs a minimum of 3 cells and always has a gap.
• "Can a gap be more than one cell?" Yes. The rule is at least one empty cell, never exactly one.
• "Do the numbers include the gaps?" No. Numbers count only filled cells; gaps are never counted.
• "Can a block touch the edge?" Yes. Blocks may start at cell 1 or end at the last cell—edges impose no extra spacing.

How to Use This While Solving

1. Read each row and column clue and compute its minimum width.
2. Compare minimum width to the grid size to find slack.
3. Mark cells that are forced filled by overlap; mark cells that fall outside every possible placement as empty.
4. Cross-check rows against columns—a filled cell must be consistent with both its row clue and its column clue.

Once the numbers click, the rest of the puzzle is pure deduction: each mark you make narrows where the remaining blocks can go.