Nonogram Solving Techniques
The 12 core techniques for solving nonograms with logic instead of guessing — organized from beginner to advanced, together with the principles behind reading the clues.
Basic
Reading the Clue Sum
First work out the minimum length that a line's number clues require.
BasicOverlap
Push a block to each end and fill the cells that always overlap.
BasicEdge Forcing
If a cell at the end of a line is already filled, the block on that side is fixed.
BasicFinishing a Line
Once a line satisfies all its clues, fill the remaining cells with X.
BasicMarking Gaps with X
Block off cells that no block can reach with an X to narrow the logic.
Intermediate
Splitting Blocks
Assign the clue blocks among the segments divided by X marks.
IntermediateRow–Column Cross-Reference
Reflect a cell confirmed in one line onto the crossing line.
IntermediateExtending from the Edge
An X near the edge pushes back where the first block can start.
IntermediateBlock Boundaries
When a run of filled cells reaches a clue's length, block off both sides with X.
Advanced
Testing for Contradiction
Assume a value for one cell; if it breaks a rule, confirm the opposite.
AdvancedForcing Chain
Once one block's place is fixed, neighboring blocks are pushed one after another.
AdvancedFull Rescan
Rescan every line involved each time you make a move.