Services like TinyURL, dickensurl.com, tini.us and many others makes long urls short. Twitter makes long URLs email friendly and save users from overflowing their 140-character limit, but shortened links can be a pain to click, wait, and then be disappointed if the link was not what you expected it to be. Now this script lets you see what’s behind those shortened urls.
The Greasemonkey Extension[link below] needs to be installed for this script to work.
If you installed this script before and have just reinstalled, it might not work soon because of the cache data. You can clear the cache data with following submenues of Firefox:
Tool -> Greasemonkey -> User Script Commands -> Reset cache data
And you can check cached URLs in console of Firefox with below:
Tool -> Error Console -> Tool -> Greasemonkey -> User Script Commands -> Show cache data