Nonograms are basically picture-Sudoku
The first time I saw a nonogram, I looked at those numbers and thought, "What am I supposed to do with these?" Then one rule clicked, and suddenly the whole grid made sense. As you fill in cells one by one, a hidden picture slowly appears — and honestly, that moment is a little addictive.
Nonograms go by a few names: picross, griddlers, picture logic puzzles. You have a grid, and each row and column has numbers listed on the outside. Those numbers tell you how the filled cells in that line are grouped. From those clues alone, you use pure logic to work out which cells to fill and which to leave empty. You never guess — there's exactly one correct solution.
Today I'll walk you through it in the same order I learned it, so you can finish your very first puzzle.
How to read the number clues
There are just three core rules. Nail these and you're halfway there.
- Each number is a run of consecutive filled cells. If a line shows
3, then somewhere in that line, three cells in a row are filled. - Multiple numbers happen in that order. A row marked
2 1means a run of 2 filled cells comes first (from the left), then a run of 1. For columns, it's top to bottom. - There's always at least one empty cell between runs.
2 1looks like "■■□■" — a gap is required between the groups. Without a gap, it wouldn't be2 1, it'd be3.
So if a 5-cell line shows 5, there's only one option: fill all five. But 1 1 needs a gap between the filled cells, so several arrangements are possible. The trick is to start with the lines you're most certain about.
Start here: find the cells that must be filled
The biggest beginner mistake is guessing at random. Never do that. In a nonogram you fill in only the cells you're 100% sure of, then use those to deduce the next ones.
The easiest certain cells come from lines that are exactly full.
- A 10-cell line showing
10→ fill everything. - A 10-cell line showing
4 5→ 4 + (1 gap) + 5 = 10, an exact fit. There's only one arrangement, so it's all locked in: "■■■■□■■■■■".
Whenever the sum of the numbers plus the mandatory gaps equals the line length, that whole line is solved. When you open a new puzzle, sweep for these lines first.
The beginner's power move: the overlap technique
This is your real first weapon. Learning it is what made my solving speed jump.
Here's the idea. When a run is large relative to the line length, the cells that overlap between pushing it all the way left and all the way right are always filled, no matter the exact position. That overlap is guaranteed.
Take a 5-cell line with a 4:
- Pushed left: "■■■■□"
- Pushed right: "□■■■■"
Overlay them and the middle three cells (positions 2, 3, 4) are filled either way. So even without knowing the exact start, you can safely fill those three. A handy rule of thumb: if the number is more than half the line length, the overlap trick works. Do this on your big-number lines right at the start, and those cells become footholds for cracking other lines.
Don't skimp on the X marks
The second common beginner mistake is focusing only on filling. Marking a cell as definitely empty is just as important. I put an X on any cell I know is blank, because those X marks unlock the next deductions.
Say a column shows 5 in a grid 8 tall. The overlap trick fills a few middle cells. Then, while solving a crossing row, you find "this cell has to be empty" — so you drop an X there. That shrinks where the column's run of 5 can sit, and often the remaining cells lock in on their own. Filled cells and X marks are partners that push each other forward.
Work the edges and corners
When I'm stuck, I always look at the edges and corners of the grid. If the first number of a line is large, that run likely starts flush against the wall.
If a row starts with 3 and the very first cell is already filled, the run must begin at the wall — so fill the first three cells and put an X on the fourth (a gap has to follow the run). A single piece of boundary information can lock in several cells at once.
Finish a line the moment it's complete
Once a line's number clues are all satisfied, every remaining cell in that line is an X. Skip this and you'll confuse yourself later. I make a habit of asking, "Are all this line's numbers placed?" — and if so, I X out the rest immediately. That way the crossing columns get clean information.
Cycle through these five moves — forced cells, overlap, X marks, edges, finishing lines — and at some point the picture is just done. Start with something small like 5×5 to get the feel, then scale up to 10×10 and 15×15.
If you want an app to practice on, try Nonogram Garden. Features like zoom, undo, X marks, and automatic line-completion checks make it easy to build the habits. It has puzzles across difficulty levels, so you can practice in exactly the order we covered today.
👉 Learn more about Nonogram Garden
Frequently Asked Questions
Are nonograms a guessing puzzle?
No. There's exactly one solution, so if you fill only the cells you can prove logically, the picture always comes together. Guessing usually leads to a contradiction somewhere and you have to erase, so filling only 100%-certain cells is actually faster.
How do I know how many empty cells sit between the numbers?
The rules only guarantee "at least one" empty cell between runs. The exact number you figure out from crossing lines. That's why you keep switching between rows and columns, growing the set of confirmed cells one at a time.
What grid size should a beginner start with?
I'd start with something small, like 5×5 or 5×10. It's perfect for learning the rules and the overlap trick, and you finish quickly, which feels great. Once it clicks, move naturally up to 10×10 and 15×15.