Popular online platforms for UPSC preparation include websites and apps like Unacademy, BYJU'S, and Insights on India. These platforms offer structured courses, video lectures, and study materials tailored specifically for UPSC aspirants. Many provide mock tests, quizzes, and forums for discussion, enhancing interactive learning. Social media groups and dedicated YouTube channels also serve as valuable resources for current affairs updates and peer support. Utilizing these platforms effectively can help candidates remain well-informed and engaged throughout their preparation journey.