Duolingo’s side business, Duo’s Taquería, has doubled its revenue to $1.3M in 2024

Free medical education from renowned organizations including the Cleveland Clinic, MD Anderson, and Medscape.

In 2025, Harvard CS50 offers 10 free certificate courses on topics such as computer science, Python, and AI.

Although Class Central lists online courses in 87 languages, courses made in English outnumber all of the others by more than six to one. English is therefore a useful language to know, even though some courses have subtitles in a range of languages. Earlier this year, we updated our list of courses to help improve your writing skills. These courses all assume some fluency in the language. But what if you do not know any English, or your English is very poor? If you do not have convenient acce