How to Solve Nonograms: A Beginner's Guide to Picross Logic

Nonograms — also known as Picross, Griddlers, or Hanjie — are logic puzzles where you fill in squares on a grid to reveal a hidden picture. The numbers around the grid tell you which squares to fill. What surprises most beginners is that you never have to guess: every good nonogram can be solved with pure logic, one deduction at a time.

This guide walks through how to read the clues and the handful of techniques that solve almost any puzzle. If you want to follow along while you read, you can open a free nonogram in Pictora and try each idea on a real grid.

1. What the numbers actually mean

Every row and every column has a list of numbers. Each number is the length of one unbroken run of filled cells, and the numbers appear in the same order as the runs. Between any two runs there is at least one empty cell.

So a row labelled “4 2” in a 10-wide grid means: a run of 4 filled cells, then a gap of one or more empty cells, then a run of 2 filled cells — reading left to right. That single rule is the whole game.

2. Start with the lines that give the most

Do not read the grid top-to-bottom. Scan for the lines that are already almost full, because they leave the least freedom:

• A line that is completely determined. If the clues plus the mandatory gaps add up to the exact width of the line, the whole line is fixed. A clue of “5” in a 5-cell row fills every cell. A clue of “2 2” in a 5-cell row is also forced: fill, fill, gap, fill, fill.
• A line with a big number. Long runs cannot move much, so they reveal cells fastest — which leads straight to the most useful technique.

3. The overlap method (your most powerful tool)

This is the technique that makes nonograms click. When a run is longer than half the line, it must cover some cells no matter where it sits. Here is how to find them:

1. Imagine pushing the run as far left as it will go.
2. Imagine pushing the same run as far right as it will go.
3. Any cell that is filled in both positions is filled in the real solution. Fill those in with confidence.

Example: a run of 8 in a 10-cell row. Pushed left it covers cells 1–8; pushed right it covers cells 3–10. The overlap is cells 3–8, so those six cells are definitely filled:

1

2

9

10

The bigger the number relative to the line, the more cells overlap. This one idea often cracks a puzzle wide open on the first pass.

4. Mark the empty cells — they matter as much as the filled ones

Beginners fill squares and ignore the rest. Strong solvers do the opposite as often as not: they mark cells that must be empty, usually with a small X. Knowing a cell is empty is just as much information as knowing it is filled, because it splits a line into smaller, easier segments.

• When you finish a run, put an X on the cell immediately before and after it — nothing else can touch it.
• If a row clue is “0” (or blank), the entire line is empty. Mark every cell with an X right away.
• If the only remaining space in a line is too small for the leftover clue, that space must be empty.

5. Work from the edges

Cells against the border have fewer places to hide. If the first clue of a row is “3” and you already know the very first cell (cell 1, on the edge) is filled, the run has nowhere to slide — it must occupy cells 1–3, and cell 4 becomes an X. Anchoring a run to an edge like this is one of the fastest ways to make progress after the overlap pass.

Be careful not to over-claim, though: if you only know that cell 2 is filled — not the edge — you cannot yet fill cells 1 and 3, because the run of 3 might sit at cells 1–3 or 2–4. All you can safely conclude is that cell 3 is filled too (it belongs to the run in both cases). Only fill a cell when every possible position of the run agrees.

6. Cross-reference rows and columns

This is where the puzzle becomes a conversation between rows and columns. Every cell you fill from a row clue also becomes a clue for its column, and vice versa. The loop looks like this:

1. Fill or X everything a row forces.
2. Look at the columns those cells touch — the new information often forces another cell.
3. That column cell feeds back into a different row.
4. Keep bouncing between rows and columns until the picture appears.

When you feel stuck, you are almost never truly stuck — you have just stopped reading a line that now has more information than it did a minute ago. Slow down and re-scan every row and column once more.

7. A quick worked mini-example

Take a 5×5 grid with the top row clue “5”. That fills the entire top row. Now every column’s first cell is filled, so every column clue must begin with a run that includes row 1. A column clue of “1” is now finished — you can X out the other four cells in that column immediately. A column clue of “3” must be rows 1–3, so you fill rows 2 and 3 and X rows 4 and 5. In just a few moves, one full row has resolved half the board. That cascade is the feeling nonograms are built around.

The top row “5” is filled; the left column’s “3” then forces rows 1–3 and empties rows 4–5:

✕
✕

Common beginner mistakes to avoid

• Guessing. If you find yourself flipping a coin, stop — the answer is readable somewhere else on the grid. Guessing on a logic puzzle usually creates a mistake you can’t see until much later.
• Forgetting the gaps. A clue of “2 2” needs a gap between the runs; people often pack them together and get stuck.
• Not marking empties. A grid full of X marks is a grid that is easy to finish. Empty cells are information, not wasted effort.
• Only reading rows. Half the clues live in the columns. Alternate.

Practice on real puzzles

Techniques stick once you use them on an actual grid a few times. Pictora is a free nonogram (Picross) app for Android with hundreds of picture puzzles across a range of grid sizes, and a hint button for the moments you’d rather take a nudge than a wild guess. It’s a straightforward place to turn the habits above into instinct.

Get Pictora free on Google Play

Frequently asked questions

Do you ever have to guess in a nonogram?

No. A well-made nonogram has exactly one solution that can be reached by logic alone. If you feel stuck, there is always another line with more information waiting to be read — you don’t need to guess, and guessing usually just hides a mistake until later.

What do the numbers in a nonogram mean?

Each number is the length of one unbroken run of filled cells in that row or column, listed in order. Between two runs there is at least one empty cell. That single rule is the whole puzzle.

What is the overlap method?

When a clue is longer than half the line, the run must cover some cells no matter where it sits. Slide the block to the far left and the far right; the cells filled in both positions are always filled, so you can fill them straight away.

Related guides

• ノノグラムの遊び方とコツ（日本語版） — the same guide in Japanese.
• All GRAMSHIFT guides — more how-to-play guides and hobby articles.