How to play Slitherlink
Join the dots into one closed loop so that each number says how many of its square’s four sides the loop uses. Also known as Loop the Loop, Fences, Takegaki.
The rules
- Draw lines between neighbouring dots, across or down — never diagonally.
- The lines must form one single closed loop.
- The loop cannot cross itself or branch: every dot has no lines or exactly two.
- A number tells how many sides of its square are part of the loop. Blank squares can have any number.
Playing Slitherlink on Puzzle Solvers
- Choose a size and a difficulty, then press New Puzzle.
- Tap a side between two dots to draw a line; tap again for ✕, again to clear. Or drag from dot to dot to draw a path.
- Numbers turn green when they have exactly the right number of sides, and the inside of the loop lights up when it closes.
- Hint explains the next deduction — zeros, full numbers, dead ends and small loops.
Using the Slitherlink solver
- Choose the size, click each numbered square and type its number (or press Sample).
- Press Solve and step through: zeros, full numbers, following the line from dot to dot, and why small loops are impossible.
A worked example
A 0 sits next to a 3. The 0 crosses its four sides, including the one it shares with the 3.
The 3 now has only three sides left and needs all three — draw them. Their ends reach dots that have only one way on, so the line keeps going.
Strategies
- Zeros first. Cross all four sides of every 0. This often gives the loop no choice nearby.
- Dots decide. A dot with two lines takes no more. A dot with one line and only one free side must continue that way. A dot with only one free side at all can’t be used.
- Corner numbers. A 3 in a corner of the grid uses both outer sides; a 1 in a corner uses neither.
- Neighbouring 3s. Two 3s side by side share the side between them and both use their far sides too.
- No small loops. Never join two ends of the same line if it would close a loop while other numbers are still unfinished.
Common mistakes
- Drawing two separate loops — there must be exactly one.
- Leaving a line ending at a dot — every line must continue.
- Treating blank squares as zero — a blank can have any number of sides.
Where it comes from
Slitherlink was published by the Japanese puzzle company Nikoli in 1989 and is also known as Fences, Loop the Loop and Takegaki.
Frequently asked questions
Can the loop touch itself at a corner?
No — each dot has at most two lines, so the loop never touches or crosses itself.
Do I have to use every dot?
No. Many dots stay unused; only the numbers have to be satisfied.
Is there always one answer?
Yes — every puzzle here is checked to have exactly one loop.
How do I solve one from a newspaper?
Open the Slitherlink Solver, type the numbers and press Solve.
Keep going
- Play Slitherlinka fresh puzzle every time
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