MIT OpenCourseWare
Free open course material from thousands of MIT courses, from intro to graduate level.
MIT’s free, open publication of course material — thousands of courses with syllabi, notes, assignments, and lecture videos, no signup or enrollment. The YouTube channel carries full lectures and short series (recent: research-topic formulation, managing research projects, grad-school applications) at a steady clip. 6.57M subscribers; the full catalog with solutions lives at ocw.mit.edu.
Source: https://www.youtube.com/@mitocw