In general the courses are free, but the optional certificates are paid.
Ranked in these QuestionsQuestion Ranking
Both edX and the classes are free.
Pro Offers courses from well known schools
edX offers courses from a wide range of well known colleges and universities including Harvard, MIT, UC Berkeley, Cornell and more.
Pro Large selection of science courses
edX offers a wide variety of science-related courses. This makes it a great resource for learning not only specific programming languages, but also other topics relating to computer science.
Pro A lot of topics (subjects)
Topics include biology, business, chemistry, computer science, economics, finance, electronics, engineering, food and nutrition, history, humanities, law, literature, math, medicine, music, philosophy, physics, science, statistics and more.
Pro Offer certificates for some courses
Con Lack of engagement in the forums
edX does not have the same forum participation from both students and instructors that other websites do, and the form of engagement often does not encourage discussion.
Con Courses aren't always available
While edX does offer some self-paced courses, you may end up waiting for the course of your choice to be run.
Con The forums are difficult to navigate
The forums are difficult to sort by date and topic, and are unintuitive to navigate.