Social networking giant MySpace will open its platform to outside application developers, a move that was made months ago by its close competitor Facebook and helped boost its popularity.

Chris DeWolfe, MySpace's CEO, made the announcement during an appearance at the Web 2.0 Summit in San Francisco on Wednesday.

The first step in opening the platform will be the creation in the next week or two of a catalog of existing widgets from third-parties that MySpace has allowed on its social network for the past four years.

Then MySpace will open its platform broadly to outside developers at some point in the coming months, said DeWolfe.

MySpace will have a "sandbox" where applications will be given test-drives by a portion of its members, to make sure the applications are safe and secure, before they are deployed to all users, DeWolfe said.

However, DeWolfe said that the overall intention is to make it easy to incorporate the applications into MySpace. "The idea is that, at the end of the day, most of these applications will come to MySpace," he said.

MySpace will also let developers generate advertising revenue from the applications they build for the site, he said.

Since opening its platform to external developers in May, Facebook has built up a catalog of about 6,000 applications, which it credits with increasing its members' engagement on the site and their enjoyment of it.

Facebook's popularity has grown very quickly this year, as the site has grown to 47 million active users today from 12 million in December, according to company statistics. Over half of its active members return to the site daily.

In June, MySpace had 114.1 million unique visitors worldwide, up 72 percent from the same month last year, according to comScore Networks. Meanwhile, Facebook had 52.2 million unique visitors in June, up 270 percent from June 2006, according to comScore.

Until now, MySpace has granted access to its platform on a case-by-case basis to developers that request it, but it doesn't have open APIs (application programming interfaces), a source of much criticism for the company in this Web 2.0 age when mashing up applications has become so popular.

DeWolfe shared the stage with Rupert Murdoch, CEO of MySpace's parent company News Corp., and both answered questions from conference chair John Battelle and from audience members.

With some people putting Facebook's value at around $15 billion, Murdoch was asked how much he thought MySpace would be worth and whether he would consider "unlocking" that value by selling the company or taking it public. Murdoch said nothing of the sort is being considered for MySpace.

The Web 2.0 Summit ends on Friday.