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35,551 courses, lecture series and talks, 222,835 lectures in all, from the world's universities and lecture halls, each played from its own source and credited to it.

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Physics

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Computer science

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Engineering

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Earth and environment

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Society and politics

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From MIT OpenCourseWare

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From Open Yale Courses

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Where the lectures come from

Every course, series and talk here is published free by its institution, under the licence or terms it states, and plays from that source's own servers: in this site's player where the source serves the file itself, in the source's own embedded player where it offers one (YouTube's, TED's, CERN's, loaded only when you press play), and otherwise on the source's own page. Nothing is copied to this site. Each course's page names its institution and teachers, states its licence as the source does (most are for non-commercial use only, and some allow no changed versions), links to its syllabus and readings there, and lists its lectures in the source's order.

Who sees what

No source rates its lectures, so each course is placed from what its source says about it: its title, subjects, department and lectures' titles, and for plain warnings its description. Nothing is left out but pornography, which none of these sources publishes.

Little OnesNo lectures: none of the sources makes any for children under six.
KidsLessons a source makes for school pupils, on mathematics, the sciences, computing, the arts, music or languages, with nothing that keeps them from children.
TweensMathematics, the sciences, computing, engineering, economics, business, the arts, music and languages, when nothing else holds them back.
TeensMedicine and health, psychology, history, politics and society, law, philosophy, religion and literature; anything that names war, crime, violence, death, drugs or disease; and everything whose subject we cannot tell.
AdultCourses and talks filed or titled with sexual themes, nudity, surgery and dissection, suicide, torture or genocide, and any whose description warns of graphic or explicit content.