Free course on freeCodeCamp
freeCodeCamp's Information Security course teaches you how to build and defend secure web applications through five hands-on projects. You'll learn to implement authentication, encrypt sensitive data, scan for vulnerabilities like SQL injection and XSS, and apply secure coding practices with libraries like HelmetJS. After completing it, you can write production code that resists common attacks. It's ideal for developers who already know basic Python and JavaScript and want to add security skills to their toolkit. The limitation: it is project-heavy and time-consuming, not a quick overview.
CybersecurityBeginner
Harvard's introduction to cybersecurity for technical and non-technical audiences. Covers threats, authentication, networking, system security, and operational security. Free to audit; certificate available via edX.
CybersecurityBeginner
TryHackMe's free Pre-Security learning path. Covers cybersecurity careers, basic networking, web fundamentals, Linux, and Windows. Designed for total beginners with no IT background.
CybersecurityBeginner
TryHackMe's flagship beginner path covering the breadth of cybersecurity: networking, web exploitation, cryptography, defensive security, and incident response. Mostly free with hands-on rooms.