How to play Slitherlink

Slitherlink is a logic puzzle in which you draw one closed loop along the edges between dots. Some cells contain numbers that describe the nearby loop.

The rules

1. A clue is the exact number of its four sides used by the loop.
2. The finished line forms one continuous closed loop.
3. The loop may not branch, cross itself, or end at a dot.
4. Separate smaller loops are not allowed.
5. Cells without numbers place no direct restriction on their sides.

A 0 uses none of its edges; a 3 uses three. There is no 4 clue because four sides would form a tiny separate loop around one cell.

Your first deductions

Mark every edge around a 0 with ×. If a clue already has its required number of lines, mark its remaining sides ×. If it needs exactly as many lines as it has undecided sides, draw all of them.

At each dot, the finished loop has either zero or two incident lines. One line entering a dot must eventually leave by one other edge; two lines close all remaining edges at that dot.

A reliable solving routine

1. Resolve 0 clues and obvious 3 patterns.
2. Recount clues after every line or ×.
3. Check dots for forced exits and forbidden branches.
4. Avoid closing a loop while unused lines or unsatisfied clues remain outside.
5. Finish only when all drawn lines belong to one closed component.

Controls on this site

Tap or click an edge to cycle line → × → empty. A line is part of your proposed loop; × records that the edge cannot be used. Your unfinished puzzle is saved automatically in this browser.

Join the Grand Loop or study the Slitherlink solving techniques for more deductions.