FutureLearn, the UK's online university platform, has reached a million students signing up for courses.
The provider of so-called Moocs (massive open online courses) says interest has been rising sharply, with 20% more UK students in the last three months of 2014.
FutureLearn carries free online courses from universities including Warwick, King's College London and Sheffield.
"We're just at the start," said chief executive Simon Nelson.
FutureLearn has reached the million-student milestone after launching in September 2013.
Set up by the Open University, it offered a UK platform for online courses in a field that was becoming dominated by US university networks.
Online courses, created by many of the world's top universities, can be studied anywhere in the world - and FutureLearn's students are in 190 countries.
Mr Nelson says he wants online learning to be able to compete with "watching TV and going on Facebook" as a way of spending spare time.
Collectively, FutureLearn students have carried out 400,000 hours of study time in the past month alone.
"Scale is one of the most exciting things about this emerging market," said Mr Nelson.
"We've attracted a very passionate group of early adopters. But we're still a relatively well kept secret so we just need to get them to spread the message for us so that tens of millions more people can benefit.
"Part of our success is creating an innovative and digitally savvy product whilst having a deep respect for the education industry and its expectations."
Mr Nelson says that many parts of the education system could be "transformed by digital".
"We're involved in one of the most exciting parts of society at the moment. Of all the sectors on their digital journey I feel that education has the most benefits to gain from its transition."
Among the students taking FutureLearn courses, the oldest is Norman Maxfield, 92, from Bedford. And among the most enthusiastic is 60-year-old Tony Lidster, who has signed up for 23 courses in a year, including psychology and forensic science.
The profile of students shows that the typical age group is between 26 and 35 and 62% of those studying are women.
FutureLearn is competing on a global stage, with the biggest competitors being Coursera, created by academics at Stanford University in California, and edX, a project jointly created by Harvard University and the Massachusetts Institute of Technology.
Coursera has more than 11.5 million students registered for courses from 118 universities and institutions.