How a nonogram works
A nonogram is a grid of empty cells with numbers beside every row and above every column. Each number is the length of an unbroken run of filled cells in that line, and the numbers are in order: left to right for a row, top to bottom for a column. Between two runs there is at least one empty cell. A row with the clue 3 1 has a run of three filled cells, then at least one gap, then a single filled cell. A clue of 0 means the whole line stays empty.
Your job is to find which cells are filled. When every row and column matches its numbers, the timer stops and the finished grid shows the picture, which is why these puzzles are also called picture logic puzzles.
Sizes on this page
| Size | Level | Cells | Good for |
|---|---|---|---|
| 5 × 5 | Easy | 25 | Learning the rules, a quick break |
| 10 × 10 | Medium | 100 | A short puzzle, the daily nonogram |
| 15 × 15 | Hard | 225 | A longer puzzle with long clues |
Random pattern makes a new grid every time, with a little more than half of the cells filled. Picture picks one of 20 small pixel pictures drawn for this page, such as a heart, a house, a tree or a cat, and tells you what you found at the end. Both kinds follow the same rules and pass the same check.
Solving techniques
Every puzzle here can be solved one line at a time. You never need to guess: in each step, at least one row or column tells you something new for sure. These are the steps that do most of the work.
- Overlap: push a run as far left as it can go, then as far right. Cells covered in both positions must be filled. In a row of 10 with the clue 7, the run starts somewhere in the first four cells, so cells 4 to 7 are always covered. For a line with several numbers, add the numbers plus one gap between each: if the total equals the length of the line, the whole line is decided.
- Gaps: once all runs of a line are placed, mark every other cell with an X. A complete line has its clue greyed out, which is a good sign to finish it with X marks.
- Edges: a filled cell at the edge of the grid starts the first run of that line, so the following cells up to the run length are filled too, and the cell after them is empty.
- Reach: a filled cell can only belong to a run that is able to reach it. Cells that no run can reach are empty.
A worked example
Take a 10 × 10 puzzle with a row clue of 8. The run of eight can start at cell 1, 2 or 3. Starting at cell 1 it covers cells 1 to 8; starting at cell 3 it covers cells 3 to 10. Cells 3 to 8 are covered either way, so you can fill those six cells right away. Now look at the columns through those cells. A column with the clue 1 that just got its filled cell is complete: mark the rest of that column with X. Those X marks in turn shorten the space in other rows, and the next overlap appears. Most puzzles are solved by going back and forth like this between rows and columns.
Marks, hints and checking
- Fill and Mark X: tap to fill, press and hold or right-click to mark a cell as empty. The mode switch lets you mark X with a normal tap. Dragging along a line applies the same change to every cell you pass.
- Greyed clues: when the filled cells of a row or column match its clue, the numbers fade. That only compares the line with its own numbers, so a greyed line can still be wrong if a crossing column disagrees.
- Check errors: shows wrong cells in red while it is on. Turn it off to play without help.
- Hint: fixes a wrong cell first, otherwise fills a cell that a single row or column forces and names that line. Undo takes back any move, including a whole drag or a hint.
How the puzzles are made
Each random puzzle is made on your device. The page fills every cell with a chance of 55 percent, computes the clues, and then runs a line solver: for each row and column it works out every way the runs can be placed among the cells already known, and keeps the cells that are the same in all of them. It repeats this over all lines until nothing changes. If every cell is decided, the clues lead to one picture only, and the puzzle is shown. Otherwise the page draws a new grid. In our tests, 50 puzzles of each size were made this way and a second, full search found exactly one solution for each of them. Making a 15 × 15 puzzle usually took a few milliseconds on a laptop and never more than a fraction of a second.
The daily nonogram uses the same generator with a random sequence seeded by the date, so everyone gets the same puzzle on the same day without any server. Your game is saved in this browser after every move. If local storage is blocked, for example in some private windows, the game still works but starts over on reload.
How to play a nonogram online
- 1Pick a size and Random pattern or Picture, then press New puzzle. Or open the daily nonogram.
- 2Start with the longest clues and fill the cells that overlap. Tap to fill, hold or right-click to mark X.
- 3Work back and forth between rows and columns. Use Undo, Check errors or Hint when you are stuck.
- 4When every line matches its clue, the timer stops and the picture is complete. Download PDF prints a puzzle for later.
Related guide
Frequently asked questions
How do I play a nonogram?
Each number beside a row or above a column is the length of a run of filled cells in that line, in order from left to right or top to bottom. Between two runs there is at least one empty cell. Fill cells until every row and column matches its numbers. Mark cells you know are empty with an X, so you do not have to remember them.
Does every puzzle have exactly one solution?
Yes. Every random puzzle is checked on your device before you see it: a line solver works through the rows and columns until each cell is decided, and a puzzle is only shown when that leads to one picture. So every cell can be found by logic from one row or column at a time, and you never need to guess. The hand-made pictures passed the same check.
How do I mark a cell as empty?
Right-click it with a mouse, press and hold it on a touch screen, or switch the mode to Mark X and tap. On a keyboard, press X. Tap or press X again to clear the mark. An X is only a note for you; it does not count toward the solution.
Can I fill several cells at once?
Yes. Press on a cell and drag along its row or column. Every cell you pass gets the same change as the first one: filled, marked or cleared. The drag stays in one line, so a shaky finger does not paint the next row. One drag counts as one move for Undo.
What do Check errors and Hint do?
With Check errors on, a filled cell that should be empty and an X on a cell that should be filled turn red. Hint fixes a wrong cell first. If nothing is wrong, it fills a cell that one row or column forces from the cells you already have, and says which line it came from. Hints are counted, and best times only count games without hints.
What is the daily nonogram?
One 10 × 10 puzzle per day, the same for everyone on that date. It is made from the date in your own time zone, so it changes at your local midnight. Your progress is saved, a reload continues where you stopped, and when you finish you can share your time without the solution.
Can I print a puzzle?
Yes. Download PDF saves the puzzle on US Letter or A4 with the clues and an empty grid, and with a solution page if you tick the box. The PDF is made in your browser, nothing is uploaded.