Nonogram clues tell you the length and order of the filled blocks in each row and column.
A clue of 4 means one block of four consecutive filled cells. A clue sequence of 2 3 means a two-cell block followed by a three-cell block, with at least one empty cell between them.
The clues describe what must exist in the line, but they usually do not tell you the exact positions directly.
One number means one block
For a line of 8 cells with clue:
4
the final line contains exactly one consecutive block of four filled cells.
One legal arrangement is:
××■■■■××
Another is:
■■■■××××
Both satisfy the clue.
The number 4 does not mean “four filled cells anywhere.” The cells must be consecutive and form one block.
Several numbers mean several blocks in order
For clue:
2 3
the final line contains two distinct blocks:
- a block of 2;
- then a block of 3.
A legal 9-cell example is:
■■××■■■××
The two blocks appear in the correct order and are separated.
This arrangement is not legal for clue 2 3:
■■■×■■×××
The block sizes are reversed: it contains a 3-block followed by a 2-block.
Clue order is fixed.
Why is there a required empty cell between clues?
In a monochrome Nonogram, adjacent clue numbers represent different filled blocks.
Without an empty separator, two blocks would merge into one larger block.
For example, clue 2 2 cannot be:
■■■■
because that is one 4-cell block.
The shortest valid arrangement is:
■■×■■
That one confirmed empty cell keeps the two clue blocks distinct.
The actual gap can contain more than one empty cell. One is simply the minimum.
How do you calculate the minimum space a clue sequence needs?
For standard monochrome clues, the minimum span is:
sum of clue values + one mandatory gap between each pair of consecutive clues
A sequence with k clues therefore needs:
sum(clues) + (k - 1)
cells at minimum.
For clue:
3 2 4
the blocks use:
3 + 2 + 4 = 9
filled cells.
There are three blocks, so at least two separator cells are required.
Minimum span:
9 + 2 = 11
If the whole line has length 11, the clue sequence has an exact fit.
If the line has length 15, there are four extra cells of placement freedom, called slack.
Why minimum span matters
Minimum span tells you how tightly the clue sequence fits.
If a set of clues almost fills the available line, the blocks cannot move very far. That can create:
- overlap;
- forced separators;
- restricted block positions;
- exact-fit segments.
The clue values alone therefore provide more information than just the total number of filled cells.
Compare these two 10-cell lines:
- clue
1— minimum span 1, leaving 9 cells of slack; - clue
4 4— minimum span 9, leaving only 1 cell of slack.
The second line is much more constrained before any crossing information is added.
How do you read row clues?
Read row clue sequences in the same order as the line:
left to right.
If the clue is:
1 4 2
the 1-block appears leftmost, the 4-block comes after it, and the 2-block appears last.
There may be additional empty cells before the first block, between blocks, or after the final block, as long as the order and separation rules are satisfied.
How do you read column clues?
Read column clue sequences:
top to bottom.
The first clue corresponds to the uppermost filled block in the column.
The final clue corresponds to the lowest block.
The visual numbers may be stacked above the grid, but their logical sequence follows the direction of the column.
What does a zero or blank clue mean?
A line with no filled blocks is completely empty.
Puzzle formats represent that state differently. A system may show:
0;- no number;
- another explicit empty-line convention.
Do not assume a blank visual area always means the same thing across every product. Follow the puzzle's stated notation.
Logically, an empty clue sequence means every cell in that row or column is empty.
Do clue numbers tell you which cells are filled?
Not usually by themselves.
A clue gives block structure, not exact coordinates.
For example, clue 3 in a 10-cell line can begin in many positions. As crossing rows or columns add confirmed states, some positions become impossible and others become forced.
Nonogram solving is the process of reducing those possibilities.
A clue can be partly solved
Suppose a line has clues:
2 5
and you have already identified the complete 2-block near the start of the line.
The 5 clue still needs to be placed later.
You should not treat the whole line as solved just because one clue is complete.
On larger lines, keeping track of which clues are resolved and which remain active can make the current constraints much easier to see.
Be careful with block identity
Filled cells do not automatically tell you which clue they belong to.
If clues are:
2 4 2
and you find two adjacent filled cells near the center, those cells might:
- be the complete first 2-block;
- belong to the 4-block;
- be part of the final 2-block;
depending on the available space and other known states.
Clue order, separators, and reach determine the identity.
This is one reason advanced Nonogram solving goes beyond simply counting adjacent filled cells.
Common clue-reading mistakes
Adding the clues and ignoring the gaps
Clue 3 2 needs at least 6 cells, not 5, because the two blocks require a separator.
Treating several clues as one total
2 3 is not equivalent to clue 5.
Reversing the order
The clue sequence is directional.
Assuming one empty cell is the exact gap size
One empty cell is the minimum. Larger gaps are legal.
Treating a known filled group as a completed clue too early
The group may still extend or belong to another clue. Confirm its identity and length first.
FAQ
What does 1 1 mean in a Nonogram?
It means two separate one-cell filled blocks in that order, with at least one empty cell between them.
What does a clue of 10 mean in a 10-cell line?
The entire line is filled.
Can there be empty cells before the first clue block?
Yes. There may be empty cells before the first block and after the last block.
Can there be several empty cells between blocks?
Yes. Standard monochrome blocks require at least one empty cell between them, not exactly one.
Do clue numbers add up to the number of filled cells?
Yes. The sum of the clue values equals the number of filled cells in that completed line. But the clue sequence also preserves block sizes and order.
Why do long clues help?
Long blocks have fewer possible positions in a fixed-length line, which often creates forced overlap.
What to learn next
Read Blocks, Runs, and Gaps in Nonograms for the vocabulary behind clue structures, then learn Minimum Span and Slack and Overlap as solving techniques.