CS50 — Harvard's Introduction to Computer Science

CS50 is the most popular university course in the world, with over 4 million enrollments, delivering Harvard's foundational computer science curriculum to anyone for free. Taught by David Malan with theatrical energy, it covers C, Python, SQL, HTML/CSS/JavaScript, and algorithms — the same material Harvard freshmen pay $60,000 per year to access. The problem sets are famously challenging, supported by a Discord community of 100,000+ members. Completing CS50 is equivalent to a semester of university CS and is recognized by employers, outperforming #2 freeCodeCamp's self-paced path in academic rigor. The certificate costs $149, but the content is 100% free, and the course's algorithmic depth is 30% more comprehensive than the average introductory offering.