A MOOC (Massive Open Online Course) is an online course designed for open, unlimited enrolment over the internet, originally popularised by platforms such as Coursera, edX, and Udacity. The defining characteristics are scale — enrolments in the thousands to hundreds of thousands — open access (no prerequisites or application), and primarily asynchronous delivery through video lectures, auto-graded quizzes, peer assessments, and discussion forums. Because of the open and unstructured nature of MOOC enrolment, completion rates are commonly low; many learners enrol out of curiosity and audit rather than complete the course, and this is a well-documented structural property rather than a platform failure. The architecture of a MOOC platform must handle very high concurrent video views during cohort starts or lecture releases, which drives heavy reliance on CDN and ABR delivery; it must also support multi-tenancy at the course level to separate content and learner data across many instructors and institutions. Certification and credentialing are often revenue mechanisms in MOOC platforms: the course is free, but a verified certificate requires payment. For a custom platform build, the MOOC model informs decisions around auto-scaling infrastructure, forum moderation tooling, and peer-review workflows. MOOCs can be run in cohort-based or fully self-paced mode; fully self-paced MOOCs have even lower completion but lower operational overhead, while cohort-based runs improve completion at the cost of scheduling complexity.
