What do the numbers in a nonogram mean?

Each number is a block of consecutive filled squares in that row or column. The blocks appear in the same order as the numbers, with at least one empty square between them.

What is the best first step in a nonogram?

Look for big clues in each line and use the overlap method: imagine the block pushed fully left and fully right — the squares covered in both positions must be filled.

Who invented nonograms?

They were created in Japan in the late 1980s, credited to Non Ishida and, independently, Tetsuya Nishio. The name 'nonogram' combines Non Ishida's first name with 'diagram'.

How to Solve Nonograms: Rules and 6 Techniques

Updated 5 October 2026 · 8 min read

Nonograms (also called Picross, Griddlers, Hanjie or Paint by Numbers) are picture puzzles solved with pure logic. They look intimidating, but a handful of techniques will take you through most puzzles. Here's how they work, with small examples you can follow line by line.

🖼️ Play a free nonogram while you read

The rules

Every row and column has a clue: a list of numbers.
Each number is a block of consecutive filled squares.
Blocks appear in the same order as the numbers (left to right, or top to bottom).
There must be at least one empty square between blocks.
A clue of 0 means the whole line is empty.

In the examples below: ■ = filled, ✕ = definitely empty, · = unknown.

Technique 1: Full and empty lines

A clue equal to the line length fills the whole line. A clue of 0 empties it. In a 5-wide grid:

clue 5 ■ ■ ■ ■ ■ clue 0 ✕ ✕ ✕ ✕ ✕

Technique 2: Lines that add up exactly

Add the numbers, plus one gap between each pair of blocks. If the total equals the line length, there's only one way to place them:

5 wide, clue 2 2 → 2 + 1 + 2 = 5 ■ ■ ✕ ■ ■ 10 wide, clue 3 1 4 → 3 + 1 + 1 + 1 + 4 = 10 ■ ■ ■ ✕ ■ ✕ ■ ■ ■ ■

Technique 3: The overlap method (simple boxes)

This is the most important technique. Imagine the block pushed as far left as possible, then as far right. Any square covered in both positions must be filled.

5 wide, clue 3 pushed left ■ ■ ■ · · pushed right · · ■ ■ ■ so · · ■ · · (the middle square is certain) 10 wide, clue 7 pushed left ■ ■ ■ ■ ■ ■ ■ · · · pushed right · · · ■ ■ ■ ■ ■ ■ ■ so · · · ■ ■ ■ ■ · · · (squares 4 to 7)

Quick rule: a block of size b in a line of length n guarantees 2b − n filled squares, if that number is positive. It works with several blocks too. Push them all left together, then all right, and compare each block with itself.

Technique 4: Cross out what can't be filled

As soon as a line's clue is complete, mark every other square in that line ✕. Squares too far from any possible block can also be crossed out. Crosses matter because they become clues for the columns that pass through them.

5 wide, clue 1, and square 3 is already filled · · ■ · · → ✕ ✕ ■ ✕ ✕

Technique 5: Edge forcing (gluing to a wall)

If a filled square touches the edge of the grid, it must be the start of the first block, so you can extend it to that block's full length and cross out the next square.

8 wide, clue 3 2, and square 1 is filled ■ · · · · · · · → ■ ■ ■ ✕ · · · ·

The same works from a crossed-out square. A filled square right after an ✕ starts a block too, and that can push the block's other end into place.

Technique 6: Reach and joining

Ask "which block can reach this square?" If only one block can reach a filled square, that block must cover it, and its length limits how far it can extend in each direction. Two filled squares close together that can only belong to the same block should be joined into one.

7 wide, clue 4, squares 3 and 5 filled · · ■ · ■ · · one block must cover both → square 4 is filled · · ■ ■ ■ · · a 4-block covering 3–5 can only be 2–5 or 3–6 → squares 1 and 7 are empty ✕ · ■ ■ ■ · ✕

A solving routine

Sweep every row, then every column, for full lines, exact fits and overlaps.
Every time you fill or cross a square, recheck the line crossing it.
Cross out completed lines straight away.
Use edges and crosses to force blocks into place.
Repeat. Each pass unlocks more squares, and the picture appears.

Hand-designed nonograms in books and apps are usually built to be solved without guessing. Randomly generated ones, like the free puzzles on FunZon, sometimes leave a spot where you need to test a square. When that happens, any grid that matches all the clues is accepted.

A bit of history

Nonograms were created in Japan in the late 1980s, credited to graphic designer Non Ishida and, independently, puzzle maker Tetsuya Nishio. The name combines "Non" with "diagram". They became popular in the UK when newspapers began printing them in the early 1990s, and later spread worldwide through handheld games under the name Picross.

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