Moodle

Moodle has been the backbone of online learning since 2002, supporting everyone from K-12 schools to massive universities. The open source model means you host it yourself and never pay licensing fees, though you'll need technical resources for setup and maintenance. Its flexibility appeals to institutions with specific requirements or large-scale needs.

The platform handles complex grading workflows, discussion forums, activity tracking, and detailed analytics. Educators can build rich interactive courses with quizzes, assignments, and peer review features. The global community contributes plugins and themes, so you're not limited to what's built in.