Severin Hacker, the co-founder of Duolingo.com who received his Ph.D. in computer science this spring, has been named to MIT Technology Review’s annual TR35 list of outstanding innovators under the age of 35.

The editors recognized Hacker for creating the online language education site, which he developed with his Ph.D. adviser, Luis von Ahn. The free education platform, which began as a research project at CMU, now offers more than 30 language courses and has more than 30 million users. Apple named Duolingo the iPhone App of the Year in 2013 and Google selected it as the Best of the Best for Android in 2013.

Last month, Carnegie Mellon announced that it would partner with Duolingo to evaluate the company’s new low-cost test for certifying the English skills of college and job applicants, Duolingo Test Center.