Play Slitherlink Online — Free
Draw a single closed loop along the grid lines so that each numbered cell has exactly that many sides of the loop adjacent to it.
Choose a puzzle
About Slitherlink
Slitherlink challenges you to draw a single closed loop along the edges of a grid, guided by numbered clues inside the cells. A clue of 0 means none of that cell’s four edges are part of the loop; a clue of 3 means three of them are. Cells without clues are completely unconstrained.
The key constraint is that the result must be one single closed loop — not multiple separate loops, not a path with open ends. This global requirement makes Slitherlink unusually elegant: local deductions cascade into global constraints, and a single forced edge near one corner can ripple across the entire puzzle.
Slitherlink was invented by Nikoli in Japan, the same company responsible for popularizing Sudoku. It appears regularly in Japanese puzzle magazines and has a devoted following worldwide. The combination of local clue logic and global loop constraint makes it one of the most intellectually satisfying pencil puzzles.
Beginners should focus on the 0-clue and 3-clue cells first — they’re the most constraining. Once you spot the patterns those create at corners and edges, the loop often fills in rapidly from both ends.
Frequently asked questions
What is Slitherlink?
Slitherlink is a logic puzzle where you draw a single non-intersecting loop along the grid lines. Clue numbers inside cells tell you how many of the four surrounding edges are part of the loop.