It does work, they have just changed the way it is implemented. It now tries to leave URLs as you posted them so that users can easily see where the link is going rather than all links being http://t.co/xxxxx
See this help article on Twitters Link Shortening service.
Having trouble fitting a link into just 140 characters?
- With Twitter’s new link-shortening feature, you can now paste a link of any length into the Tweet box on Twitter.com and it will be
shortened to 19 characters. You no longer have to worry about fitting
a long link into the 140 character limit!
- If you want to keep using your favorite link shortening service, you can continue to do so.
- Note: If you enter a URL shorter than 19 characters into the Tweet box, our system will still "shorten" it to 19 characters.
(example: https://about.me/ will take up 19 characters in your Tweet
even though its URL is only 16 characters long.)
This is what posting a long URL used to look like:
This is what posting a long URL looks like now:
Fig.1 After 13 characters of a URL are entered, a message appears to
let you know that the link will be shortened.
Fig. 2 YouTube URL has been assigned a t.co link ID, but the link
will appear as a shortened version of the original URL.
Whenever you post a link in one of your Tweets, it will automatically
be shortened. See for yourself!
- Start typing or paste a long URL into the Tweet box.
- After you’ve entered the first 13 characters of a URL, a message will appear at the bottom of the Tweet box, letting you know that the
link will appear shortened. (Fig. 1)
- Notice that even if you’ve reached the character limit, you can continue to add text to the URL with no consequence.
- Once the Tweet is posted, it will be assigned a t.co link ID, but the link will appear as a shortened version of the original URL, so people who see your Tweet will know the site they are going to when
they click the link (Fig. 2, above). Yep! It’s now that easy.
Note: Twitter's link service (http://t.co) is only used on links posted on Twitter and is not available as a general shortening
service. To learn more, see our help page on Twitter's Link Service
- Sometimes URLs can be harmful, so please be careful when clicking on links that were shortened using an external link shortening
- Always check to see what website you're on before giving out your password or downloading any software.
- URLs converted by Twitter’s link service are checked against a list of potentially dangerous sites, and when there’s a match, users will
be warned before they continue.
- Our Safe Tweeting help page has more information on keeping your account secure.