MySpace already allows users to customize their personal profile pages. But they generally must go off the site, grab the lines of programming code they are interested in and cut and paste that into their profiles. Now, users will be able to add those features more directly.

Under the MySpace Developer Platform, an outside e-mail provider can write a program that sits on the personal home page users see when they log on. Users can check for new messages right there.

Or — instead of taking visitors to another site to view photo albums — a photo-sharing service can write a program that appears on a MySpace profile page that friends visit.

The company unveiled details of the previously announced platform Tuesday and said developers would be able to write and test interactive programs, called "widgets," on up to five users for a month before making them available to the broader MySpace community.

MySpace's launch of a developer platform follows a May decision by its smaller rival social network, Facebook, to open its platform to developers. That has proven a boon for music-sharing startup iLike.com, photo-sharing service Slide Inc. and other companies.

Those applications, in turn, have helped make Facebook more popular, although it still ranks second behind MySpace, a unit of News Corp.

By bringing features from other sites with the developer program, MySpace hopes users will have fewer reasons to leave the site — and view ads elsewhere.

Amit Kapur, MySpace's chief operating officer, said all applications would be treated equally, even though the openness means competitors could siphon traffic from MySpace's own products — such as the MySpaceTV feature that competes with Google Inc.'s YouTube.

"If somebody builds a better feature than we do, we want to see that succeed," he said. "It's shortsighted for us to think we can do everything."

Age, hometown, photo albums and video clips posted on MySpace profiles will be among the data available for incorporation into the widgets. The company said developers would have access only to data already publicly visible, and users can keep that information from developers by restricting profile access to friends only.

MySpace will let developers sell ads, sponsorships and products on special pages assigned to each application, but no ads will appear on the widgets themselves.