How to play nonograms

A nonogram is a picture hidden in a grid. The numbers beside each row and above each column tell you how the filled squares in that line are grouped. Fill the right squares and the picture appears. Every puzzle on nonograms.io can be solved by logic alone, so you never have to guess.

What is a nonogram?

A nonogram is a logic puzzle that draws a picture. You get an empty grid with numbers along the top and down the left side. Each number says how long a run of filled squares is in that row or column, and you work out which squares to fill until the picture shows up.

Different communities call the same puzzle different things. Many people know it as picross, you will also hear griddlers and hanjie, and the rules are the same under every name. On nonograms.io we say nonogram.

The puzzle comes from Japan, and it is usually credited to Non Ishida and Tetsuya Nishio, who published such puzzles independently in 1987. The name "nonogram" is linked to Ishida. It is a pen-and-paper puzzle at heart and still plays well with nothing but a grid and some patience.

The rules

• Each number is a run of consecutive filled squares.
• Runs appear in the order listed, left to right or top to bottom.
• Runs are separated by at least one empty square. "3 1" means three filled, at least one gap, then one filled.
• A 0 means the line is empty.
• Mark squares you know are empty with an ×. Crosses are notes to yourself, and they're what unlock the next step.

Five techniques

1. 1. Overlap

   Slide a run as far left as it can go, then as far right. Squares covered both times must be filled.

   Clue7

   Before

   After

   The bigger the number compared with the line, the more you get. Start every puzzle here.

2. 2. Lines that fill exactly

   Add the runs and the gaps between them. If the total equals the line's length, there's only one arrangement.

   Clue4 5

   Before

   After

   ×

3. 3. Out of reach

   Once a square in a run is filled, the run can only stretch so far from it. Cross everything beyond.

   Clue3

   Before

   After

   ×××××

4. 4. Edges push inward

   A filled square touching the edge must be the start of the first run, so fill the rest of that run and cross the square after it.

   Clue3 2

   Before

   After

   ×

5. 5. Gaps too small

   A space between crosses (or a cross and the edge) that's shorter than every run that could go there must be empty.

   Clue3

   Before

   ×

   After

   ×××

A worked example: a 5×5 from blank to finished

Here is a complete little puzzle. The row clues are 1 1, 5, 3, 1 and 1, from top to bottom. The column clues are 1, 3, 4, 3 and 1, from left to right. We'll solve it one line at a time, using only the techniques above. Each diagram shows a single row or column before and after.

1. Step 1: row 2

   Start with the biggest clue. A 5 in a line of 5 fills the whole row.

   Clue5

   Before

   After

2. Step 2: column 3

   Column 3 has a 4 in a line of 5, so overlap fills the middle three squares. The square we filled in row 2 agrees.

   Clue4

   Before

   After

3. Step 3: row 4

   Row 4 has a single 1, and column 3 just told us where it is. Cross the other four squares.

   Clue1

   Before

   After

   ××××

4. Step 4: column 1

   Column 1 wants one filled square, and row 2 already supplied it. Everything else in the column is empty.

   Clue1

   Before

   ×

   After

   ××××

5. Step 5: column 5

   Column 5 is the mirror image of column 1, so it goes the same way.

   Clue1

   Before

   ×

   After

   ××××

6. Step 6: row 3

   Row 3 has a 3, and its two end squares are crossed. Only three squares are left, so all three are filled.

   Clue3

   Before

   ××

   After

   ××

7. Step 7: row 1

   Row 1 is "1 1" with its end squares crossed. Three squares are left, and a 1, a gap and a 1 need exactly three.

   Clue1 1

   Before

   ××

   After

   ×××

8. Step 8: column 3

   Back to column 3. Its top square is now crossed, so the 4 has to sit in the bottom four squares.

   Clue4

   Before

   ×

   After

   ×

9. Step 9: row 5

   The last row has a 1, and column 3 has put it in the middle. Cross the rest and the board is done.

   Clue1

   Before

   ××

   After

   ××××

The result is a small tulip. Notice that you never had to guess: every step followed from a clue and a square you already knew. Larger boards work the same way, just with more lines to keep moving between.

Putting it together

Rows and columns feed each other. Every square you fill or cross in a row is new information for the column it sits in. Work round the grid: apply the five techniques to each line, then move on to the lines you just changed. When nothing obvious is left, look for the longest clues and the most crowded lines first. Our hardest (expert) boards also need lookahead: suppose a square is filled, follow the logic, and if it leads to a contradiction, the square must be empty. That is still logic, not guessing.

Common mistakes

Almost everyone makes these at first. None of them is a sign you are bad at nonograms.

• Treating a run as a whole line

  A clue of 3 means three filled squares in a row somewhere in the line, not that the line starts with three. Place it as far left as it can go and as far right, and only trust the squares both placements share.

• Forgetting the gap between runs

  With a clue of "2 2" the runs need at least one empty square between them, so the shortest possible arrangement is five squares, not four. Add the gaps when you count.

• Never crossing squares

  Crosses look like extra work, but they are what make the later techniques fire. A line with a few crosses breaks into short segments, and short segments are easy to reason about.

• Staying in one row for too long

  Each row only knows so much by itself. When a line stops giving you anything, move to the columns it crosses. They have just learned something new.

• Guessing when stuck

  On our boards a guess is never needed. If you are stuck, you have usually missed a cross or a tight gap. Try the hint, which points you to a row or a column that still has a forced move. If you suspect an earlier fill was wrong, turn on "Only when I press Check" in Settings and use Check, which counts the wrong squares without showing where they are.

• Reading a clue backwards

  Row clues read left to right and column clues read top to bottom. Taking a "1 3" for a "3 1" is easy when you are tired, so say the clue out loud before you commit.

Questions about nonograms

Do I ever have to guess?

No. Each puzzle here has exactly one solution, and you can reach it by logic alone. Easy, medium and hard boards need only line-by-line reasoning. Expert boards need lookahead, where you test a square and follow the consequences, but that is still deduction.

What does a 0 clue mean?

A 0 means the whole row or column is empty. Cross it out and let the lines it crosses benefit.

Where should I start on a new puzzle?

Look for the biggest clues compared with their line, and for lines where the runs and gaps add up to the full length. Those give you filled squares without any other information. Then work back and forth between rows and columns.

What size should a beginner pick?

Start with a 5×5 to see how clues work, then a 10×10 on easy. At 10×10 you get a real picture and the techniques on this page are enough to finish it.

Are the puzzles free?

Yes. Every size, the daily puzzle and co-op rooms are free to play in your browser. Your progress and settings are kept in your browser.

What can I do if I make a mistake?

By default, a wrong square is marked as soon as you place it, so you can undo it straight away. If you'd rather find mistakes yourself, choose 'Only when I press Check' in Settings and use Check, which counts the wrong squares without showing where they are.

Can I play with other people?

Yes. Create a room, send the link, and everyone paints the same board together in real time.

How do I zoom in on a big board?

Pinch the board with two fingers, or tap the magnifier under the board: it zooms in to finger-sized squares, and tapping it again fits the whole board back on screen. On a keyboard, + and − zoom in and out and 0 fits the board.

Is there a daily puzzle?

Yes. The daily puzzle is the same for everyone on a given date, in a 10×10, 15×15 or 20×20 size depending on the day of the week, and the last two weeks of daily puzzles are listed on the daily page.