OER Commons
OER Commons is a digital library of more than 500,000 open educational resources gathered from schools, universities, and education bodies around the world. It does not hold one type of material; it indexes whole courses, single modules, lesson plans, videos, interactive simulations, and assessments across every subject and level, from early years to postgraduate. Every entry is described with structured metadata (subject, education level, material type, and the licence that applies), and the whole thing is run by the Institute for the Study of Knowledge Management in Education.
Most of your work happens through the website, where you search and filter by subject, level, and curriculum standard, then click through to each resource. There is no single dump of the entire collection, and OER Commons often acts as a catalogue pointing at materials hosted elsewhere, so a RAG pipeline here means crawling out to the linked items rather than ingesting one clean file. The upside is the metadata: it is good enough to triage what is worth fetching before you spend time on it. Expect a mix of HTML pages, PDFs, and embedded media once you follow a link.
It suits education-focused systems: a tutoring assistant, a lesson-planning tool, or anything that needs teaching content mapped to subjects and grade levels. The reach across disciplines and formats is the real strength, and because the collection is curated you are drawing on vetted educational material rather than the open web.
Licensing is the thing to watch. Resources carry a spread of Creative Commons licences and a few other open terms, so rights vary item by item: some permit commercial use, some do not, and some require share-alike. Treat commercial use as unclear at the collection level and check each resource before building on it. Quality and depth also vary, since contributions come from many institutions.
For consistent, book-length material, the Open Textbook Library and LibreTexts are steadier; come to OER Commons when you want the widest spread of formats and lesson-level resources.
Related sources
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CEFR Companion Volume Descriptors
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