Width: Height:
Symmetry: None 2 Way 4 Way
Difficulty: Easy Medium Hard
Select a size: Select a puzzle:
Or enter puzzle code:
Enter grid size: Width: Height:
Or enter puzzle code:
The internet's foremost slitherlink app!

It was originially written in PHP (way too slow). Rewritten in Java (still slow). Now it's javascript (slower than Java, but getting faster all the time thanks to the browser wars!), which is nice and universal. The method is simple: generate a loop, tweak it a bit for aesthetics, and fill the grid with numbers. Then remove the numbers individually while checking for solvability. The solver is pattern based up to medium difficulty, and uses guessing on hard. It is not based in any way on the "loopy" program by Simon Tatham, unlike almost every other similar site on the internet, although if it was it would be faster.

The handmade slitherlinks have been made by myself over a period of several years; more are always being added to the site.

All content on this page, including generated puzzles, is copyright 2015-17 Kakuro Online.

Check out the iOS app Slitherlink Infinite

Questions? Comments? Media Inquiries? Want to brag about your slitherlink solving prowess? Feel free to contact me: slitherlinks@gmail.com
I don't see any puzzles?
Your browser is probably out of date. This site uses technology only available in newer browsers that are compatible with HTML 5. It's also possible that you have disabled Javascript.

The generator is slow.
Yes, especially on the hard setting. Those on mobile devices or those wishing for larger (15x15+) puzzles should stick to medium. On desktop computers, Chrome seems to be the fastest browser for generating puzzles.

The solver failed to solve my puzzle.
Yeah, it's not as good as it could be. There are obvious (to humans) deductions that it can't figure out yet. You might notice strange solutions, those usually occur when the puzzle is unsolvable. The solver stops itself if it runs into an invalid situation, so make sure your puzzle is inputted correctly. Improvements are in the works, I promise!

Enter puzzle code? What is that?
A puzzle code is a text description of a slitherlink puzzle. An example of a small puzzle would be 3x3:c3a2a31. First number is the width of the puzzle, second is the height. After the colon a letter represents a number of blank spaces between numbers. a = 1, d = 4, up to z. The numbers represent the clues of the puzzle. You can use this to enter your own puzzles, or import puzzles from other sources.

Are you sure all the puzzles are solvable?
All the handmade ones are definitely uniquely solvable. But they can be very difficult. The higher numbered ones are generally harder. Regarding the generated puzzles, they are also definitely solvable. You may, very (very) rarely, come across one with more than one solution. Sorry about that.

What does guess mode do?
It allows you to try a certain line of logic with the ability to clear it out if you get to an invalid position. It's very useful, probably necessary even, on the harder handmade puzzles, or on the hard generated puzzles, which use guessing.
When you click on the guess mode button, all the lines and exes you have marked will turn blue, and will not be able to be changed. You can then mess around with the rest of the puzzle. Clicking the clear guess button will remove the lines and exes that aren't blue. Clicking the guess mode button again while still in the mode will turn your marks black again, keeping anything that was there, including any guesses you had.

That easy puzzle was way more difficult than the medium!
That will happen, especially if a symmetry other than "None" is chosen. It will be improved in the future. Poor thing is still in beta.

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