When submitting a URL to Needle we'll add it to our database along with a normal numeric ID (BASE10), that ID will then be converted to a "short id" that is appended to our domain in the final short link. (http://⇒.mp/<NEEDLE>)
Normal URL shorteners however only converts the numeric ID using latin characters like "A-Za-z0-9-_", the alphabet with numbers, dash and the underscore, all in all it adds up to 62 characters (BASE62) making it possible to store 62 URLs in a one-character "short id", 3844 URLs in a two-character "short id", 238 328 URLs in a three-character "short id" and so on.
We felt that only using BASE62 to make the "short id" was non-efficient, so we came up with the idea of using a whole lot of unicode characters! When we convert our numerical IDs we will not only use the latin alphabet with numbers, but we will also make use of the extended latin alphabet, geometric shapes, icons, japanese hiragana and katakana (with variations), a whole lot of kanji, hangul, tibetian characters and more adding up to a total of 41000 characters, something we quite humorously call "BASE41000"!
So we can store 41 000 URLs in a one character "short id", over 1.5 billion (1 500 000 000) URLs in a two-character "short id", over 68.5 trillion (68 500 000 000 000) URLs in a three character "short id", and so on. With that said, it's more likely that our system will break down before our "short id" will ever reach four characters, or even three characters for that matter...
Oh, and don't worry if you or the people you're sharing the links with doesn't have installed support for unicode characters, even if you don't see the characters the browser will know what character it is and redirect you as usual. As long as the website can turn it into a link (today that shouldn't really be a problem) it'll work just as well as any other urls!
Needle was more or less just a simple experiment to check just how many links we could store in as little space as possible, when we figured out that we could store way ridiculous amounts we laughed, but slightly after that we had no idea what to do with the "tools" we had made to do the experiments.
So we did as anyone would do, but it online just for the heck of it! With funding from the Swedish Government and the King himself we published this nice little thing here on a Swedish language domain name that no one will ever remember.
The Needle Teams is just a bunch of rocket scientists and world travellers making spaceflights to mars in our spare time, make absolute zero-freezers, drinking lakes and chopping down trees with our bare fists in the winter, we don't like trees. We also run several countries in Southeast Asia.
True story. I should know, I wrote it myself.