Nonograms are one of the most satisfying logic puzzles ever created. By following number clues along the edges of a grid, you gradually reveal a hidden picture — no guessing required, just pure logical deduction. Whether you are a first-time solver or coming back for a refresher, this guide covers everything you need to know about nonogram rules.
A nonogram is a picture logic puzzle played on a rectangular grid. The objective is to determine which cells should be filled in (colored) and which should be left empty, ultimately revealing a hidden image. The puzzle is guided entirely by numeric clues provided along each row and each column of the grid.
Nonograms go by many names around the world. In Japan, they are widely known as Picross (short for "picture crossword"), popularized by Nintendo's handheld puzzle games. In the UK and Europe, you will often hear them called Griddlers, Paint by Numbers, or Pic-a-Pix. In Japan and Korea, the terms Hanjie and O'ekaki are also common. Regardless of the name, the rules are always the same.
The puzzle was independently invented by Non Ishida in Japan and Tetsuya Nishio in 1987. Since then, nonograms have appeared in newspapers, puzzle magazines, mobile apps, and dedicated websites worldwide, attracting millions of enthusiasts who enjoy the unique combination of logic and art.
Every nonogram follows a simple set of rules that are easy to learn:
1. Number clues describe groups of consecutive filled cells. Each row and each column has a sequence of numbers beside it. Each number tells you the length of a consecutive group of filled (colored) cells in that line. For example, a clue of "3" means there is a single run of exactly three filled cells somewhere in that row or column.
2. Groups appear in the given order. If a row has the clue "2 4 1", there is first a group of 2 filled cells, then a group of 4, then a group of 1, reading from left to right. For columns, the groups appear from top to bottom.
3. At least one empty cell separates each group. Between any two groups of filled cells, there must be one or more empty (unfilled) cells. This gap is crucial for distinguishing one group from the next.
4. Fill or mark X. You either fill a cell (it is part of a group) or mark it with an X to indicate it must remain empty. Marking cells with X is optional but highly recommended — it helps you eliminate possibilities and avoid mistakes.
5. No guessing required. A properly constructed nonogram has exactly one solution, and it can always be reached through logic alone. If you find yourself guessing, take a step back and look for clues you may have missed.
Let us walk through a simple 5x5 puzzle to see the rules in action.
Column clues (top to bottom): [1], [3], [5], [3], [1]
Row clues (left to right): [1], [3], [5], [3], [1]
Step 1: Start with the largest clues. Row 3 has a clue of "5" — that means all 5 cells in that row must be filled. Fill the entire row. Similarly, Column 3 has a clue of "5", so fill the entire column.
Step 2: Use overlap logic. Row 2 has a clue of "3" in a 5-cell row. The group could start at position 1, 2, or 3. The cells that overlap in every possible placement are positions 2, 3, and 4. But we already know cell 3 is filled from Step 1. Positions 2 through 4 are confirmed filled. Since we need exactly 3, cells 1 and 5 must be X.
Step 3: Repeat for remaining rows and columns. Apply the same overlap reasoning to Row 4 (clue "3") and Rows 1 and 5 (clue "1"). For rows with clue "1", the filled cell must align with Column 3 (the only column that allows it based on what we have already deduced).
Step 4: Verify. Check every row and column against its clue. If all clues are satisfied, the puzzle is complete. In this case, the solution reveals a diamond shape.
Always start with the largest clues. Rows or columns whose clues add up close to the total line length are the easiest to solve first. A clue of "7" in a 10-cell row already tells you that at least 4 cells in the middle must be filled.
Use the overlap technique. This is the most fundamental nonogram strategy. Slide each group as far left as possible, then as far right as possible. Any cells that are filled in both positions must be filled in the solution.
Mark empty cells with X. When you determine that a cell cannot be filled, mark it immediately. These X marks constrain future deductions and prevent errors.
Work from both edges. Clues at the start and end of a line often lock into place quickly, especially when combined with X marks from neighboring lines.
Check completed lines. Once a line is fully solved, verify it against the clue. Mark any remaining unfilled cells as X to help solve intersecting lines.
Be patient and systematic. Scan all rows, then all columns, and repeat. Each pass usually reveals new information that was not visible before.