Just put your URL you want to shorten after http://4sp.in/shortenapi?url= and it will return the short link for it.
You must include the protocol, http:// ftp:// https:// AND the whole destination URL must be URLencoded.
If the URL is valid and can be shortened, the API will return the short URL, nothing more.
If the URL is NOT valid, the API will return the word: ERROR.