Shortened links have probably been one of the factors that fueled Twitter’s explosive growth and have in turn benefitted from it. But their biggest advantage holds at the same time possible security threats, since the user cannot see where the link is pointing. Over time many solutions for expanding them appeared, from sites to scripts and Twitter clients. Now, it looks like Twitter has introduced the feature in it’s web version: hover your mouse over a short URL and the tooltip will reveal the original link. It’s similar to the concept presented some time ago by Chris Messina, although without the ability to copy the expanded URL.
I’m not sure how long ago the feature was introduced; I don’t recall reading about it anywhere and I rarely use the Twitter website. I prefer to alternate between Brizzly and TweetDeck for Chrome, both of them having different advantages over native Twitter. But since the surveys are showing that most users are checking Twitter through the site, it will be a welcomed addition for them. Personally I still prefer the way Brizzly implemented URL expansion, replacing the short URLs inline. This makes it much easier to scan the addresses and enables you to see the destination and browse tweets with keyboard shortcuts at the same time.