Zero Width Shortener [...] is a URL shortener that shortens URLs using spaces that have zero width, making them invisible to humans.
It seems like this url shortener doesn't store your url, but encodes it into an invisible path in its url. I think this is a very interesting application of zero width / invisible chars, which itself is an interesting topic. I've read about zero width spaces being inserted into posts to detect and track copy pasting.
Back to the topic, I think this is a nice idea, but it's not usable on all services, because some just show the url encoded version of those chars.