Because of technological advances — among them, the greatly improved quality of online delivery platforms, the ability to personalize material and the capacity to analyze huge numbers of student experiences to see which approach works best — MOOCs are likely to be a game-changer, opening higher education to hundreds of millions of people.

To date, most MOOCs have covered computer science, math and engineering, but Coursera is expanding into areas like medicine, poetry and history. MOOCs were largely unknown until a wave of publicity last year about Stanford University’s free online artificial intelligence course attracted 160,000 students from 190 countries. Only a small percentage of the students completed the course, but even so, the numbers were staggering.

“The fact that so many people are so curious about these courses shows the yearning for education,” said Molly Corbett Broad, president of the American Council on Education. “There are going to be lots of bumps in the road, but this is a very important experiment at a very substantial scale.”

So far, MOOCs have offered no credit, just a “statement of accomplishment” and a grade. But the University of Washington said it planned to offer credit for its Coursera offerings this fall, and other online ventures are also moving in that direction. David P. Szatmary, the university’s vice provost, said that to earn credit, students would probably have to pay a fee, do extra assignments and work with an instructor.

Experts say it is too soon to predict how MOOCs will play out, or which venture will emerge as the leader. Coursera, with about $22 million in financing, including $3.7 million in equity investment from Caltech and Penn, may currently have the edge. But no one is counting out edX, a joint venture of Harvard and the Massachusetts Institute of Technology, or Udacity, the company founded by Sebastian Thrun of Stanford, who taught the artificial intelligence course last year.