Duolingo’s market value ($13.49B) now eclipses both Coursera and Udemy combined, driven by explosive user growth and surging quarterly revenue.

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

In 2021, Udacity consolidated its enterprise focus, launched fewer free courses, but tripled scholarships.

If you’re interested in learning the guitar, there’s a course for you. In this guide to the best guitar courses, there are several beginner courses to choose from, plus some specific styles to explore if you already know the basics. The guitar is a popular and versatile musical instrument. It’s portable (especially the acoustic guitar), and you can play melodies or strumming both solo and in a band. It lends itself beautifully to many musical styles, from flamenco to classical, jazz, blues, fol