Harvard CS50 review

CS50x is Harvard University's introduction to computer science, taught by David J. Malan, and it is free to audit online through edX. It is the deepest course on this list. Instead of teaching one language, it covers abstraction, algorithms, data structures, security, software engineering and web development, using C, Python, SQL and JavaScript plus CSS and HTML. Harvard says it is for majors and non-majors alike, with or without prior programming experience. Learners who earn a satisfactory score on 9 problem sets and a final project are eligible for a certificate, and a verified certificate costs $219. The cost is effort. Harvard lists 10 to 20 hours per week, and the problem sets are real programming assignments. It is not a tap-through phone app, so plan to work on a laptop. If you want gentle, game-like lessons, start with Mimo or Sololearn and come back to CS50 later.

Who it is for

Committed beginners who want a university-level foundation for free

Price

Free to audit; optional verified certificate for $219.

Audit for Free Add a Verified Certificate for $219
Quoted from the vendor pricing page on November 12, 2026.

Key features

• Covers C, Python, SQL and JavaScript plus CSS and HTML
• Topics include algorithms, data structures, security and web development
• 9 problem sets and a final project
• Self-paced, with a stated 10 to 20 hours per week
• Optional verified certificate on edX for $219

Strengths and weaknesses

• Strength: Free to audit, from Harvard's School of Engineering and Applied Sciences
• Strength: Teaches how to think about problems, not just one language's syntax
• Strength: Open to majors and non-majors with no prior programming experience
• Weakness: Heavy workload of 10 to 20 hours per week
• Weakness: Starts with C, which is harder than Python for many beginners
• Weakness: Lecture and problem-set format, not a phone-friendly app

Key facts

• Price: Free to audit
• Certificate: $219 verified certificate
• Time: 10 to 20 hours per week, self-paced
• Languages: C, Python, SQL, JavaScript, CSS, HTML
• Platform: edX

Where it ranks

Harvard CS50 is No. 4 in our Best Learn To Code Apps verdict.