Free Nonogram Solver Online
Stuck on a nonogram puzzle? Our free online solver can help you find the solution instantly. Simply enter the row and column clues from your puzzle, click Solve, and watch as the algorithm reveals the hidden picture. This tool is perfect for verifying your solutions, learning solving techniques, or tackling puzzles that have you stumped.
The solver uses a line-by-line logical deduction algorithm, the same fundamental approach that human solvers employ but executed with perfect precision. The algorithm works by analyzing each row and column independently, finding cells that must be filled or must be empty regardless of the final arrangement. It then iterates repeatedly over all rows and columns, using newly discovered information to make further deductions. This process continues until the entire grid is solved or no more progress can be made through pure logic alone.
Understanding how the solver works can actually improve your own solving skills. The core technique is called overlap analysis. For each line (row or column), the algorithm considers the leftmost possible placement of all clue blocks and the rightmost possible placement. Any cells where a block appears in both the leftmost and rightmost positions must be filled. Similarly, cells that no block can ever reach must be empty. By applying this analysis across every row and column repeatedly, the solver gradually reveals the complete picture.
For most well-designed nonogram puzzles, this line-by-line approach is sufficient to find the complete solution. Some extremely difficult puzzles may require trial-and-error or backtracking techniques, but our solver handles the vast majority of puzzles you will encounter. Enter your clues below to get started.
Enter Your Puzzle
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Click or drag to draw your puzzle. Row and column clues are computed automatically.
How the Algorithm Works
The nonogram solver implements an iterative constraint propagation algorithm. Here is a step-by-step breakdown of the process:
1. Overlap Analysis: For each row and column, the algorithm computes where each clue block could possibly be placed given the current state of the grid. Cells that must be filled in every valid arrangement are marked as filled.
2. Empty Cell Detection: Cells that cannot be part of any valid block placement are marked as empty (crossed out). This provides additional constraints for perpendicular lines.
3. Iteration: The algorithm alternates between processing all rows and all columns. Each pass may reveal new information that allows further deductions in subsequent passes.
4. Convergence: The process repeats until no new cells are determined in a complete pass, indicating the puzzle is either solved or requires more advanced techniques.