Facebook unveils new 'Like' button

The social-networking service, at a conference for developers in San Francisco, said its technology requires other companies to install a "Like" button on their websites that users can click on to signal their interest in a piece of content, such as a band or an article.

The user's approval then shows up on his or her Facebook page, with a link back to the other site.

The buttons, which was scheduled to go live last night, transmit data about user activity back to Facebook, supplementing a user's profile or appearing in a user's activity stream. Websites that add the buttons can offer customisations for users, such as showing visitors what articles their friends liked or what restaurants they reviewed.

Facebook said dozens of partners have signed up to use the technology, including ticketing site Fandango.com and news site CNN.com. It said it would allow a group of pre-vetted websites, such as Docs -- a new online service from Microsoft -- as well as Yelp and Pandora, to offer customisation without requiring their users to log in or click connect.

In a keynote address, Facebook chief executive Mark Zuckerberg depicted the new technology as an expansion of Facebook's vision and a new way to organise the information on the Web. For years, he said, the company has focused on tying together people on the web, mapping out who knows whom.

Now, Facebook wants to map out connections between people, places and things, gathering more explicit information about users' specific interests in order to deliver them a more personalised experience on Facebook and on other sites.

He called it "most transformative thing we have ever done for the web".

Mr Zuckerberg did not elaborate on how Facebook would handle the data gathered from other websites, a move sure to attract interest from privacy advocates already concerned with how much Facebook knows about its users.

Until now, the social network has been trying to get other Web sites to connect to its service via a product called Facebook Connect. Released in 2008, it allows users to log-in other Web sites with their Facebook login to see which of their friends are also using the site, for instance.

But Mr Zuckerberg called those integrations "fairly superficial" compared with the types of integrations the "Like" technology would allow. For instance, upon visiting a music-listening website a Facebook user could instantly hear music that they had "liked" across the web.