Free online courses — also called Massive Open Online Courses — have quite a year.

It’s been seven years since these courses rose to prominence, when a few Stanford professors decided to offer their courses online free. Since then over over 900 universities have launched over 11,000 courses.

And in its seven years these Massive Online Open Courses (MOOCs) have achieved new milestone: 100+ million learners!

And I’ve been keeping track of these courses the entire time over at Class Central, ever since they rose to prominence. Class Central is a search engine, discovery platform, and review site for MOOCs. More than 18 million people have used Class Central to find their next course.

Class Central’s home page.

At the end of every year, I do an extensive analysis of the MOOC space. To help me with analysis, I send the top MOOC providers a set of questions, one of them being the top enrolled courses of 2018.

The list below contains the top enrolled courses from the major MOOC providers: Coursera, edX, Udacity, and FutureLearn. Combined, these providers represent a big chunk of the MOOC learners (70+ million!).

You can also find this list on Class Central which I built using Class Central’s newest feature: Custom Lists. We just launched this a few days ago to help you organize your learning. You can build lists of courses for learning different topics, then share these lists withs friends, family, and the interwebs.

Without further ado, here are the most popular free online university courses of 2018: