bit.ly is a utility that allows users to shorten a long URL, share it, and then track the resulting usage.

For example, you can turn this link:

Into this link:

This makes it easier to include the link in an email or Twitter post without it breaking or taking up too much space.

Every bit.ly link has an Info page that shows the number of clicks and other relevant data.

For example, to get to the Info page for this bit.ly link:

You’ve got several options:

Click “Share” below each bit.ly link in your History, or on any Info page. You can easily share this bit.ly link via Twitter, Gmail, Facebook, and your default Email client. You can also use the bit.ly info bookmarklet to share a link while you are on a page (get the bit.ly bookmarklets here). Bonus: bit.ly links are great for sharing because they won’t break in emails and they never expire.

bit.ly tracks the total number of clicks pointing to a single long link. Signed in bit.ly users receive a unique bit.ly link that lets them track clicks and other data separately, while still seeing totals for all bit.ly links pointing to the same long link. Users not signed in all share the same bit.ly link.

The Conversations section of the Info page show Twitter posts and Friend Feed items containing links to a bit.ly link. Conversations also show the number of comments found on the page a bit.ly link points to. For example, if a bit.ly link points to a blog post that has 3 blog comments, these comments will appear in the Conversations section.

bit.ly uses several sources to gather content for the Metadata section:
1. bit.ly looks at the metatags of the page a bit.ly link points to.
2. bit.ly uses Open Calais to semantically tag text and URLs found on the page.
3. bit.ly uses MetaCarta to analyze the content type of each file a bit.ly link points to. If the file is a picture, bitly extracts EXIF data. If it is a music file, bit.ly extracts ID3 tags.

Currently, bit.ly Search simply looks for Twitter posts containing a search term you enter and returns the posts that contain both your term and a bit.ly link. The results also show the number of clicks on each bit.ly link.

Many users click on bit.ly links outside browsers with no referrer data, which makes it difficult for us to identify what client they are using. Direct Traffic includes people clicking a bit.ly link from:
• Desktop email clients like Microsoft Outlook or Apple mail
• AIR applications like Twirhl
• Mobile apps like Twitterific or Blackberry Mail
• Chat apps like AIM
• SMS/MMS messages
• It also includes people who typed a bit.ly link directly into their browser
We have a program to register applications with bit.ly so they will appear as separate, named clients in the Referrer table. If you’re interested in becoming a Registered Application with Bit.ly, please fill out this form: http://bit.ly/rVpPK

bit.ly offers bookmarklets for different scenarios - the “Sidebar” bookmarklet uses a slide-out panel to show traffic, conversations, and a history of shortened links. The “bit.ly” bookmarklet is geared toward Twitter users, and lets users include highlighted content as well as the bit.ly link in a Twitter post. See the Tools section for more details.

No. Each link bit.ly issues is unique and will not be re-used, so you can be confident users will arrive at the correct site. Some URL shorteners issue links a character shorter than bit.ly, but have to re-use them because there is an upper limit to the number of character combinations.

A “redirect” is a technique for making a web page available under many URLs. When you shorten a link with bit.ly, you are redirecting a click from bit.ly to the destination URL. A 301 redirect is the most efficient and search engine friendly method for webpage redirection, and is what bit.ly uses. Because bit.ly doesn’t re-use our links, we consider our redirects to be permanent.

bit.ly maintains a highly reliable and redundant system with the goal of making our service - especially existing links - available at all times. We are also in the process of developing an archive system to make sure that links are available beyond our systems.

Bit.ly filters all links through several independent services to check for spam, suspected phishing scams, malware, and other objectionable content. We currently include Google Safe Browsing, SURBL, and SpamCop in our operations. For Firefox and Chrome browser users, we also have a Preview Plugin that allows you to view more information about a link before clicking. If you are a Twitter user, similar preview features are offered by Tweetdeck (we’ve got a writeup of how it works here).