# Context In 2012, the Massachusetts Institute of Technology (MIT) and Harvard University launched open online courses on edX, a non-profit learning platform co-founded by the two institutions. Four years later, what have we learned about these online “classrooms” and the global community of learners who take them? # Content This report provides data on 290 Harvard and MIT online courses, 250 thousand certifications, 4.5 million participants, and 28 million participant hours on the edX platform since 2012. # Acknowledgements Isaac Chuang, a professor at MIT, and Andrew Ho, a professor at Harvard University, published this data as an appendix to their paper "HarvardX and MITx: Four Years of Open Online Courses".