edX is a major digital education initiative launched in 2012 by Harvard University and the Massachusetts Institute of Technology (MIT). The programme is designed to offer free online learning in the form of "MOOCs", or massive open online courses. Harvard and MIT both invested $30m in edX early last year and were subsequently joined in the initiative by the University of California, Berkeley, the University of Texas System, Wellesley College and Georgetown University. edX has recently announced that it has just doubled its number of university partners to 12, including its first members from outside the US. In this interview with Physics World, edX president Anant Agarwal explains why he is so confident that the initiative can transform online learning.