Udemy is one of the largest online course platforms for e-learning in the world. It’s a marketplace where creators can design their own course offerings around their subject area of expertise. Students receive a completion certification at the end of each course. Subjects include coding and programming, data science, marketing, design, personal development, music, health and fitness, and more.

While these courses can be free and cost as much as hundreds of dollars, instructors earn varying levels of revenue from the platform depending on how students are finding their courses.