What the Clue Numbers Mean

Every row and column in a nonogram has a clue — one or more numbers listed beside or above it. These numbers describe the blocks of filled cells that appear in that line. Reading clues correctly is the foundation of solving any nonogram.

Each number represents exactly one consecutive group of filled cells in that line. The number tells you how many cells are in the group. The order of numbers tells you the order the groups appear, from left to right in rows and top to bottom in columns.

A Single Number

A clue of 5 in a row means there is one block of exactly 5 consecutive filled cells somewhere in that row. The block can start at any position that fits, but it must be exactly 5 cells long — not 4, not 6.

Everything else in the row (cells not part of this block) must be empty. Your job is to figure out exactly where the block of 5 is placed.

Multiple Numbers

A clue of 3 2 means there are two blocks in that line: one block of 3 cells, followed by one block of 2 cells. The block of 3 comes first (left/top), the block of 2 comes second (right/bottom).

Crucially, there must be at least one empty cell between any two blocks. This gap is not optional — the rules require blocks to be separated. The gap can be one or more cells wide, but it must exist.

A clue of 1 1 1 means three separate single-cell blocks, each separated by at least one empty cell. In a row of 5 cells, the only valid arrangement is: ■ _ ■ _ ■

The Zero Clue

A clue of 0 means the entire row or column is empty — there are no filled cells at all. Mark every cell in that line with an X immediately. This is one of the best free moves in nonogram solving: a zero clue costs no analysis and fills an entire line.

Reading Row Clues

Row clues are read left to right. The first number describes the leftmost block, the second number describes the next block to the right, and so on. The blocks appear in that exact order from the left edge of the row to the right edge.

Example: row clue 4 1 2 in a 12-cell row. There is a block of 4, then a gap (at least 1 empty), then a block of 1, then another gap, then a block of 2. The minimum space needed is 4 + 1 + 1 + 1 + 2 = 9 cells, leaving 3 cells of slack across the 12-cell row.

Reading Column Clues

Column clues follow the same rules, but orientation is vertical. The first number describes the topmost block, the last number describes the bottommost block. Blocks appear in top-to- bottom order, just as row clues appear in left-to-right order.

No other difference exists between row and column clues. The logic is identical — only the axis changes.

Checking Your Reading

Before making any move, always verify you have read the clue correctly. Common mistakes:

• Reading multi-digit numbers as separate clues. A clue of "12" is one block of twelve cells, not a block of 1 and a block of 2. Multi-digit numbers appear on larger grids and are easy to misread.
• Forgetting the gap rule. Two separate numbers always require at least one empty cell between their blocks.
• Reversing column direction. The first number in a column clue is the topmost block, not the bottommost. Reading columns from bottom to top causes systematic errors that are hard to catch.

Calculating Minimum Space

For any clue, you can calculate the minimum space required to fit all blocks. Add up all the block sizes, then add (number of blocks − 1) for the mandatory gaps between them.

Example: clue 3 2 1 requires 3 + 1 + 2 + 1 + 1 = 8 cells minimum. In a 10-cell line, you have 2 cells of slack. In an 8-cell line, the arrangement is completely determined — only one valid solution exists.

Comparing minimum space to line length gives you immediate information. Whenever minimum space equals or is close to line length, the blocks are constrained and cells can be filled.

Start Solving

With clue reading understood, you have everything you need to start solving. Easy puzzles use simple clues on small grids — perfect for practicing clue reading before tackling the more complex clues of medium and hard difficulty.