What is a Slitherlink solver?
A Slitherlink solver is an online tool that completes a loop puzzle from its numbered clues. Slitherlink is also searched for as Fences, Loop the Loop, Loopy, Sli-Lin and Takegaki, but the core rule is the same: draw one continuous closed loop along grid edges.
This page is built for people searching for Slitherlink solver, Slitherlink puzzle solver, online Slitherlink solver, Fences puzzle solver, Loop the Loop solver, Slitherlink answers and Slitherlink helper. It lets you solve a complete puzzle, check a partial grid or reveal only the next logical move.
- Solve a Slitherlink puzzle from a book, app, newspaper or worksheet.
- Enter known lines and crosses before solving.
- Check whether a partial loop still has a valid completion.
- Find one forced line or blocked edge without revealing the full answer.
How to use this Slitherlink solver
Choose the grid size first, then create the board. Click inside a square to cycle through blank, 0, 1, 2 and 3. Click an edge between two dots to cycle through a loop line, a cross and a blank edge.
Press Solve to fill the full loop. Press Check to confirm that your current lines and crosses can still fit a valid solution. Press Next move when you want one hint: the tool highlights a single edge and explains why it should become a line or a cross.
- Use blank clue cells where the original puzzle gives no number.
- Use crosses for edges that you already know cannot be part of the loop.
- A 0 clue immediately makes all four surrounding edges crosses.
- A completed clue forces the remaining surrounding edges to crosses.
- A dot with two lines cannot accept any more lines.
Slitherlink rules used by the solver
The solver follows standard Slitherlink rules. Each numbered square must have exactly that many loop edges around it. Empty squares place no direct count restriction on their four sides.
Every used dot must have exactly two loop lines touching it, so the loop cannot branch or stop. At the end, all line segments must belong to one single closed loop, not several small loops.
- 0 means no surrounding edges are lines.
- 1, 2 and 3 mean exactly that many surrounding edges are lines.
- A dot may have zero lines or two lines, never one, three or four.
- The loop may not branch, cross itself or leave loose ends.
- The final answer must be one connected loop.
Next move logic and Slitherlink strategies
The Next move button starts with the same deductions many human solvers use. If a clue already has enough lines, the remaining edges around it are crosses. If every remaining edge is needed to reach the clue total, those edges become lines.
The solver also checks dot degree logic. A dot with two lines must reject every other touching edge. A dot with one line and only one open edge left must use that edge. If local rules are quiet, the helper searches valid completions and shows an edge that is forced in all of them.
- Clue complete: remaining edges around the clue become crosses.
- Clue needs all: all remaining edges around the clue become lines.
- Dot complete: a dot with two lines blocks its other edges.
- Avoid dead ends: a dot with one line needs a second line.
- Forced edge: every valid solution agrees that the edge is a line or cross.
Why a Slitherlink puzzle can be impossible or ambiguous
A Slitherlink becomes impossible when a clue cannot reach its required count, when a dot is forced into a dead end, or when the current lines cannot form one connected loop. A single wrong line near a 2 or 3 can create a contradiction several steps later.
A puzzle can also be ambiguous. That means more than one loop satisfies the same clues. Published Slitherlink puzzles normally aim for one unique solution so every line and cross can be justified by logic rather than guessing.