Georgetown University is joining one of the most prominent ventures in online higher education, a Web platform known as edX that provides courses from elite schools to a global audience for free.

The addition of Georgetown to edX marks the latest development in a fast-growing movement that aspires to connect the ivory tower to the world.

Millions of people have signed up this year on Web sites for massive open online courses, or MOOCs, which offer self-paced learning through video lectures, tests, homework, discussion boards and other digital interfaces. Advocates say MOOCs will democratize higher education and spark a teaching revolution on campuses. Skeptics call it little more than brand promotion.

EdX, which Harvard University and the Massachusetts Institute of Technology launched in May, hosts MOOCs from those schools and the University of California at Berkeley. The University of Texas system joined in October and Wellesley College last week. Like Georgetown, they plan to add MOOCs to edX next year.

Another MOOC platform, Coursera, which launched in April, hosts classes from Johns Hopkins University, the universities of Maryland and Virginia, and 30 other major U.S. and foreign institutions.

For Georgetown, the nation's oldest Catholic university, securing an agreement to work with the site led by MIT and Harvard was a major coup. Two hundred colleges and universities have approached edX about possible partnerships. But the site's leadership has been extremely selective.

"We would like to have the best courses from the best professors from the best universities," edX President Anant Agarwal said. "Georgetown certainly brings that."

Georgetown President John J. DeGioia, who helped oversee an accreditation review of Harvard a few years ago, said he and Harvard President Drew Gilpin Faust began discussing MOOC ventures over the summer. DeGioia said it became clear that it would be possible to work with edX as he met with Agarwal at the Web site's headquarters in Cambridge, Mass., in mid-September.

"We're truly honored" to be invited to join edX, DeGioia said in an interview.

Details of the arrangement, including financial terms and what online courses Georgetown will offer, remain to be settled. The university expects to build MOOCs in social sciences and humanities, drawing on strengths in areas such as international relations, law and public policy. The courses would launch by next fall.

Georgetown officials, echoing counterparts at U-Md., U-Va. and elsewhere, said they hope the MOOC experiments will shed light on how to improve campus instruction. What are called learning analytics — a data trove mined from student interaction with MOOCs — could provide rapid feedback to professors, enabling them to retool lectures and seminars.

"We're all searching for the optimal blend of face-to-face experience and online experience," said Robert Groves, Georgetown's provost. "And the world hasn't figured that out yet."

The emergence of MOOCs has prompted talk about how they might shake up the economic model of higher education, especially if students are able to use them to earn credit toward a degree. That's no small question for private institutions such as Georgetown, MIT and Harvard, where annual tuition and fees for an undergraduate student exceed $40,000 a year.

For now, though, prominent universities are not offering credits for their MOOCs.

For edX, securing Wellesley and now Georgetown might signal the beginning of a new phase of growth as the site navigates a global market just beginning to take shape. To date, Coursera has moved faster than edX in many respects.

Coursera counts more than 2 million registered users. Agarwal said edX has surpassed 500,000 unique users — a figure he called "staggering."

As of Friday, Coursera listed 208 MOOCs and edX nine.

Coursera's courses cover a variety of material: introduction to astronomy (Duke University), women and the civil rights movement (U-Md.) and introduction to computer networks (University of Washington), among many topics. A coming course from Brown University is titled "The Fiction of Relationship," with a reading list that includes Herman Melville, Franz Kafka and Virginia Woolf.

So far, edX's offerings are heavy in technical fields — for example, circuits and electronics (MIT), introduction to computer science (Harvard) and foundations of computer graphics (Berkeley).

EdX officials say they plan to roll out new courses soon, including some in the social sciences and humanities.

"I actually think we're moving quite quickly," said Michael D. Smith, dean of the faculty of arts and sciences at Harvard and a member of the edX governing board. "We've got a pipeline of courses coming out now. You'll continue to see us accelerate."

EdX is nonprofit, while Coursera is for-profit. That may explain, in part, why Coursera is growing at a faster pace. Both platforms are considering various ways to generate revenue without charging tuition.

Analysts say that edX is seeking to carve out a high-quality niche in the market.

"The interesting question is, how good is the thing that's free?" said Kevin Carey, an education analyst at the New America Foundation. "It doesn't surprise me that they're being deliberate about it. If they're putting their brand names behind this effort in a very public way, you absolutely want to mitigate against the risk of people saying, 'This is no good.' "

Jeff Selingo, editor at large for the Chronicle of Higher Education, said MOOCs could evolve into a recruiting tool.

"Remember, all these universities scour the world for the most talented students," Selingo said. "They're always trying to find that diamond in the rough."

Eventually, he said, universities may weigh whether a prospective student has passed a MOOC: "Why shouldn't that be considered as part of your portfolio for admission?"