How to Solve Nonograms

You can finish most puzzles with two ideas: fill the long blocks first, then use overlap to force the middle. Here's the whole routine, in order.

Step 1: read the clues

Each number is a block of filled squares. 2 3 means a block of two, a gap, then a block of three. The order never changes.

Step 2: fill whole lines first

If a clue equals the line length, fill the whole line. In a 5-wide row, 5 fills every square. Free cells, no thinking.

Step 3: use overlap

This is the one trick that carries you. If a block is longer than half its line, some squares are forced in the middle.

• Block of 3 in a 5-wide line: the third square is always filled.
• Block of 6 in a 10-wide line: squares 5 and 6 are always filled.

Fill the forced squares first. They usually open the next move.

Step 4: mark your empties

An empty square you've proved is just as useful as a filled one. Mark it with an X. Every X removes a possibility permanently.

Step 5: work the intersections

After you change a row, check the columns that cross it, then back again. Row, column, row, column. That loop is the whole game.

Step 6: count from the edges

Slide a block to the far left, then to the far right. The squares covered both times are forced. It's overlap, but it also works when a line has several blocks.

Step 7: don't guess

Feeling like guessing means you missed a deduction. Go back and re-read a line you think you've finished. Guessing just builds a board full of contradictions.

Go practise

Start on 5×5 and use steps 2–4. When that's comfortable, move to 10×10, then 15×15. Stuck? The Hint button applies one deduction and shows you why. That's the fastest way to learn. Prefer to watch the same logic off the board? Paste the clues into the free nonogram solver and step through Next step one cell at a time.