Puzzle guides › Nonogram
How to solve nonograms: a step-by-step guide with a worked example
Nonograms look hard at first, but every puzzle on Puzzlenest can be solved one line at a time with a few simple rules. We'll learn them by solving a real 5×5 puzzle together.
The rules in one paragraph
Each number beside a row or above a column is the length of a run of filled squares in that line, in order. Between two runs there is at least one empty square. A clue of 2 1 means: some empty squares (maybe none), two filled, at least one empty, one filled, then maybe more empty squares. Your job is to work out which squares are filled. You never need to guess.
The puzzle
Here are the clues for a 5×5 picture. Rows are numbered 1 to 5 from the top, columns A to E from the left.
| Row | Clue | Column | Clue | |
|---|---|---|---|---|
| 1 | 1 1 | A | 2 | |
| 2 | 5 | B | 4 | |
| 3 | 5 | C | 4 | |
| 4 | 3 | D | 4 | |
| 5 | 1 | E | 2 |
Step 1: full lines
Rows 2 and 3 have the clue 5 in a line of 5 squares. The whole row is filled. Fill both rows completely.
. . . . . # # # # # # # # # # . . . . . . . . . .
Step 2: overlap
Column B has the clue 4. The run of four can start at row 1 (rows 1-4) or at row 2 (rows 2-5). Either way, rows 2, 3 and 4 are filled. The same is true for columns C and D. So row 4 gets filled squares in B, C and D.
. . . . . # # # # # # # # # # . # # # . . . . . .
This is the overlap rule, the most important technique in nonograms: slide a run as far as it can go in both directions, and the squares it covers both times must be filled.
Step 3: finished lines give you empty squares
Column A has the clue 2, and rows 2 and 3 are already filled. That's the whole run, so A1, A4 and A5 are empty. Mark them with ×. Column E is the same: E1, E4 and E5 are empty.
× . . . × # # # # # # # # # # × # # # × × . . . ×
Row 4's clue 3 is now complete too (B, C, D), which agrees with what we have.
Step 4: the tricky row
Row 1 has the clue 1 1, and only B1, C1 and D1 are still open. Two single runs need a gap between them, and in three squares the only way to fit them is B1 filled, C1 empty, D1 filled.
× # × # × # # # # # # # # # # × # # # × × . . . ×
Step 5: finish the columns
Column B now has rows 1 to 4 filled, which is its run of 4, so B5 is empty. Column D is the same, so D5 is empty. Column C has C1 empty, so its run of 4 must be rows 2 to 5: fill C5. Row 5's clue 1 is now satisfied by C5.
× # × # × # # # # # # # # # # × # # # × × × # × ×
It's a heart. Every step followed from the clues, with no guessing.
Techniques for bigger puzzles
Overlap with several runs
For a clue like 6 2 in 10 squares, push both runs as far left as they go (squares 1-6 and 8-9) and as far right as they go (squares 2-7 and 9-10). The run of 6 covers squares 2 to 6 in both positions, so those five are filled. The run of 2 covers square 9 both times, so square 9 is filled. A clue only gives overlap when its total length (the runs plus one gap between each) is more than half the line, and here it is 6 + 1 + 2 = 9.
Edges and walls
If a filled square is next to the edge of the grid or next to a ×, the run must start there. Extend it to its full length and put a × after it.
Reaching
If the first run in a row is 3 and the first filled square you know is in position 5, then positions 8 and beyond can't belong to that run. Squares that no run can reach are empty.
Splitting by ×
A × splits a line into smaller pieces. A piece that's too short for any remaining run must be empty. For example, a gap of two squares between two × marks can't hold a run of 3.
Where to practice
Start with the 5×5 daily puzzle on our nonogram page, then move up to 10×10 when the overlap rule feels natural. Our generator only publishes puzzles that can be solved line by line, exactly like the example above.