Massive open online courses (MOOCs) have been hailed as an educational revolution that has the potential to override borders, race, gender, class and income (see go.nature.com/hanoau). However, a survey of active MOOC users in more than 200 countries and territories has revealed that most students on these courses are already well educated — and that they are predominantly young males seeking to advance their careers.

Our data are drawn from 34,779 responses to a July 2013 survey by the University of Pennsylvania, USA, of participants in 32 course sessions of the online education service Coursera (see https://www.coursera.org/penn). We found that 83% of surveyed students already had a two- or four-year post-secondary degree (see 'MOOCs are not reaching the disadvantaged', red bars), with 44.2% reporting education beyond a bachelor's degree (see go.nature.com/cvjp8u).

Furthermore, the prior educational standard among MOOC students across the world far exceeds that of the general population in their own countries (see figure, blue bars; source: www.barrolee.com).

This educational disparity is particularly stark in Brazil, Russia, India, China and South Africa, all of which are prime candidates for MOOC education. In those countries, almost 80% of MOOC students come from the wealthiest and most well-educated 6% of the population.

We found that men account for 56.9% of all MOOC students (and 64% in countries outside the Organisation for Economic Co-operation and Development; OECD). Also, almost 70% of MOOC students are already in employment (these data are not shown).

Far from realizing the high ideals of their advocates, MOOCs seem to be reinforcing the advantages of the 'haves' rather than educating the 'have-nots'. Better access to technology and improved basic education are needed worldwide before MOOCs can genuinely live up to their promise.