◌ Loops
How to Play Slitherlink
Slitherlink (also called Loop the Loop or Fences) is a logic puzzle invented by the Japanese publisher Nikoli. You draw a single closed loop along the lines of a grid, guided only by number clues — no arithmetic, no vocabulary, pure deduction.
Every well-made Slitherlink has exactly one solution, and you can always reach it by logic alone. This guide covers the rules and the core techniques that take you from your first grid to weekend-hard boards.
The rules
- Draw one single closed loop along the grid lines. The loop never crosses itself and never branches — one unbroken path.
- Each numbered cell tells you exactly how many of its four sides the loop uses. A 0 means none of its sides are used. Blank cells are unconstrained.
- Mark sides you know are empty with a small cross. Crosses are just notes to yourself — but they're often as valuable as the lines.
Solving techniques
1. Start with the zeros
A 0 means none of that cell's four sides is on the loop — cross them all out immediately. Those crosses restrict the neighbouring cells and dots, and often trigger a chain of easy deductions. Zeros are always the first thing to clear.
2. Corner clues
A 3 in a corner of the grid always uses its two outer sides — the loop has no other way to give it three segments. A 1 in a corner is the mirror image: its two outer sides are always empty, because a line entering that corner would be forced to turn and use two sides.
3. Adjacent threes
Two 3s side by side force three parallel lines: the edge between them and the two outer edges. Two 3s touching diagonally each take their two far corner sides. These patterns are worth memorising — they appear constantly.
4. Count at every dot
Every dot on the grid touches either exactly two loop segments or none at all. If a line arrives at a dot and two of the three remaining exits are crossed, the line must leave through the last one. And if three exits of a dot are crossed, the fourth is a cross too.
5. Never close the loop early
The loop is one single closed path, so you may not complete it while clues are still unsatisfied. If drawing a segment would seal off a small loop too soon, that segment is a cross. On the hardest boards, test a candidate segment mentally: if it leads to a contradiction, the opposite marking is correct — solvers call this a “what-if”.
Frequently asked questions
Do Slitherlink puzzles require guessing?
No. A well-made Slitherlink has a unique solution reachable by logic alone. Our weekday puzzles never need guessing; weekend puzzles may need one short what-if — testing a segment mentally and rejecting it on a contradiction.
What do the numbers in Slitherlink mean?
Each number says how many of that cell's four sides are part of the loop. A 0 means none, a 3 means three. Blank cells can use any number of sides.
What size is the daily Loops puzzle?
Loops is a 6×6 Slitherlink published daily. Difficulty ramps through the week — Monday is the gentlest, Sunday the hardest — and everyone gets the same board on a given date.
Is it free to play?
Yes. The current week's puzzles are free, no account needed. An account only adds cross-device progress sync — it never gates play.