(AP) -- On the short-messaging service Twitter, space is at a premium: You've got 140 characters to make your point, and you probably don't want to waste half of it on a super-sized link to your latest YouTube obsession.
There's an increasingly popular quick fix: a free URL shortener. On one of these Web sites, you can plug in a long Internet address, known as a URL, and it will assign you a much shorter one that is easier to post in e-mails, on Twitter, Facebook or anywhere else. Some link-shrinkers let you personalize the new address with a unique phrase such as your name, or show you how many people click the link after you've posted it.
This convenience may come at a cost, though. The tools add another layer to the process of navigating the Web, potentially leaving a trail of broken links if a service suddenly closes shop. They can also make it harder to tell what you're really clicking on, which may make these Lilliputian links attractive to spammers and scammers.
URL shorteners have been around for several years to offer alternatives to long Web links that were too unwieldy to paste into e-mails. Perhaps the oldest and most popular is TinyURL, a free service started in 2002 by Kevin Gilbertson, a unicycle enthusiast from Blaine, Minn., who was tired of seeing URLs get split up in e-mails related to his online unicycle forum.
Now the rise of Twitter and other social Web sites that encourage users to share small bursts of information has spawned several TinyURL followers, whose names run the gamut from the very short - tr.im - to the not long - notlong.com.
Link compression is just the beginning. More and more of these allow users to see all sorts of details like where a link is showing up around the Web and where the people clicking on it are located.
And while several of them started out as side projects, some of their creators believe they can make money off little links. At least one claims its users can profit, too.
Twitter has directly contributed to the prominence of two services in particular: TinyURL and bit.ly, which began in July as a project at New York-based Web media incubator and Twitter stakeholder Betaworks.
Until recently, Twitter automatically shrank lengthy links by running them through TinyURL. But this spring Twitter switched its default link shortener to bit.ly after finding TinyURL unreliable, said Alex Payne, one of Twitter's lead engineers. (Gilbertson said Twitter didn't contact him about the issues or the change.)
Bit.ly is seeing growth that Betaworks Chief Executive John Borthwick called "pretty amazing." About 100 million bit.ly URLs are clicked on per week.
Betaworks has spun off bit.ly as its own company, bolstered by $2 million from investors that included O'Reilly AlphaTech Ventures.
Bit.ly is looking into three different ways to make money, Chief Operating Officer Andrew Weissman said. Bit.ly might create an advertising-supported site that tracks the most popular online trends, which it can spot by analyzing what people are using its link-shortening service for. Or it might sell that data to search engines and media companies that want to know what's hot. Or it could offer a paid service to companies and major individual users.
URL shrinker LinkBee, which was created in July by Toronto-based Web media company Jolt Media Group, believes it already has a business model that will work: It shows people an advertisement before taking them to a Web site behind a shrunken link, or it puts an ad at the top of the page being linked to.
Generally, LinkBee splits the resulting advertising revenue 50-50 with people who use it to shrink links. Users who refer others can get a cut of LinkBee's portion of that new user's ad revenue. If you just want to abridge a URL without including ads, LinkBee lets you do that, too.
For now there's no tie between the ad LinkBee shows and the underlying Web link. Eventually, though, founder Chris Pavlovski hopes to make that connection. So if a user posted a link on Twitter to a page about golf, for example, LinkBee might first show an ad for golf clubs to someone clicking on that link.
LinkBee could encounter resistance from Web sites to its method of placing ads on top of pages it is linking to. News publishers sued a small referral site, TotalNews, over this sort of technique in the mid-'90s. But Pavlovski said nobody has complained about LinkBee's use of the practice.
"If anything, they're happy to receive the traffic," he said. Pavlovski said his service creates about 35,000 URLs each day, with about 70 percent attached to an advertisement.
But popularity and convenience don't eliminate the potential risks of these link loppers. If so many services are springing up, chances are some will just as quickly disappear. And if a URL shortening service goes down, the links created with it could lead nowhere.
Another worry is that you're not likely to know exactly where a truncated link will take you. So you could be directed to unsavory or illegal content or something malicious like a computer worm. This means URL shortening services need to keep an eye on the kinds of sites their users are linking to, said Ivan Arce, chief technology officer for Boston-based Core Security Technologies.
Several URL reducers said they do protect against spam. And some services - SafeURL, for example - let you preview a shrunken link's destination page, but this is not usually done automatically. There are also solutions like LongURL, which lets you plug in short addresses and see where they really point.
If you're not into the whole brevity thing, there are URL lengtheners, too. DickensURL will convert Web addresses into Charles Dickens passages. Of course, quotes from "Great Expectations" tend to be longer than 140 characters, so DickensURL also offers a compact link, which leaves plenty of room for tweeting.
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