A massive repository of 100M+ course-specific documents, now a part of the Learneo group. In 2025, it integrated QuillBot for AI writing and Symbolab for step-by-step math. While its library of previous exams and lecture notes is unrivaled, its high monthly cost and 'unlock' system are often criticized by students on a budget.

The world's largest course marketplace, currently being absorbed into the Coursera ecosystem (announced Dec 2025). While it offers 210,000+ courses, it has faced criticism for a 'subscription-first' pivot that de-prioritizes individual purchases and significantly reduces instructor payouts. In 2025, it integrated 'Udemy Intelligent' AI to help students find learning paths and summarize transcripts.