MITx MOOCs are Massive Open Online Courses. These courses are open to learners from around the world and are not limited to a certain number of enrolled learners. MITx MOOCs are generally created from or inspired by residential MIT courses and span the full breadth of MIT's academic programs.
All MITx MOOCs offer an audit (free) enrollment track, which provides access to all of the core course material. Many, but not all, MITx MOOCs also offer a certificate (paid) enrollment track, which allows learners to earn a course certificate upon passing the course.
Courses are offered in sessions, and learners enroll in a specific session. Each session has defined start and end dates, enrollment periods, and—if a certificate is available—a payment deadline, which may vary by course. Learners can enroll at any time during the enrollment period and access the course during the session dates. Course content may be released gradually on a schedule or made fully available at the start, and courses may be self-paced or instructor-paced. After the session ends, learners can no longer submit coursework or earn a certificate, but they retain indefinite access to the course content.