* Coursera: Known for its partnerships with top universities and organizations, offering a wide range of courses, specializations, and degrees. It's often cited as one of the largest and most well-known.
* edX: Similar to Coursera, edX boasts partnerships with leading universities and offers a diverse catalog of courses. It also frequently features courses with verifiable certificates.
* Udemy: A massive online learning platform with a vast library of courses, often focusing on practical skills and professional development. It distinguishes itself with a significant number of courses created by independent instructors.
* FutureLearn: Focuses more on university-level courses and partnerships, similar to Coursera and edX, but often with a greater emphasis on humanities and social sciences.
* Udacity: Often focuses on more technical skills and career-focused programs, often with a strong emphasis on nanodegrees (more structured and intensive programs than individual courses).
Ultimately, the "most popular" institute for *you* will depend on your specific learning goals, preferred learning style, and budget. Each platform has its own strengths and weaknesses.