computer science / intro
Learn Computer Science from Scratch, Free
The best free courses to go from "I've never coded" to actually understanding how computers and software work, including the single most popular CS course on Earth. No cost, no prerequisites, and a clear order to follow.
Computer science isn't just coding. It's learning how to think about problems the way a computer scientist does: breaking them down, spotting patterns, and reasoning about efficiency. That mindset is what makes you able to learn any language or tool later, which is why starting with a real CS foundation (not just a syntax tutorial) pays off for years. The courses below teach exactly that, from top-tier universities, entirely free. The good news for a beginner is that you're spoiled for choice; the challenge is knowing where to start and in what order, which is what this guide sorts out. If you only pick one, start with Harvard's CS50: it's the most beloved intro course anywhere, and for good reason.
01 · THE FAMOUS ONE
Start with CS50
Harvard's introduction to computer science is a rite of passage: brilliantly taught, rigorous, and completely free.
- CS50x — Harvard's Intro to Computer Science ↗The complete course, free: C, Python, SQL, data structures, and how computers actually work. Famous for a reason.cs50.harvard.edu
- CS50 on edX (with optional certificate) ↗The same course hosted on edX — audit it free, or pay only if you want the verified certificate.edx.org
02 · UNIVERSITY INTROS
More world-class intro courses
Prefer Python or a different teaching style? These are excellent alternatives.
- MIT 6.0001 — Intro to CS and Programming in Python ↗MIT's full intro course on OpenCourseWare — lectures, notes, and problem sets, all free.ocw.mit.edu
- Khan Academy — Computer Science ↗Free, approachable lessons on algorithms, cryptography, and information theory — great for building intuition.khanacademy.org
03 · LEARN BY BUILDING
Hands-on coding paths
Want to build real projects while you learn? These free, project-based curricula are the best in the business.
04 · HOW TO LEARN IT
How to actually get through a CS course
Free courses have one catch: no one makes you finish them. The people who succeed treat a free course like a real one: a schedule, the exercises, and finishing what they start. Here's the approach that works:
Pick one course and commit to it. Don't sign up for five. Choose CS50 (or an alternative above), set a weekly pace, and above all do the problem sets. CS is learned by writing code, not watching lectures. Type every example yourself, and don't move on until it runs.
05 · FAQ
Frequently asked questions
What is the best free course to learn computer science?
Harvard's CS50 is the most widely recommended free introduction to computer science. It is rigorous, beginner-friendly, and covers programming, data structures, and how computers work, and it is free to audit. MIT's intro courses and freeCodeCamp are excellent alternatives.
Can I really learn computer science for free?
Yes. World-class universities like Harvard, MIT, and Stanford publish full courses for free, and project-based platforms like freeCodeCamp and The Odin Project are entirely free. The main investment is your time and consistency, not money.
Do I need to be good at math to learn computer science?
To start programming and learn the basics, you only need comfort with school-level math. Some advanced areas like theory and machine learning use more math, but you can learn those foundations gradually as you go rather than needing them upfront.
How long does it take to learn computer science?
You can grasp programming fundamentals in a few months of consistent study with a course like CS50. Building broad, job-ready computer-science knowledge across algorithms, systems, and projects typically takes one to two years of regular practice.
Should I get a CS degree or learn online?
Both can lead to a career. A degree offers structure and credentials, while self-teaching with free courses and a strong project portfolio is a proven path for many developers. The free courses here cover much of the same material a degree does.