Popular online platforms providing courses for UPSC exam preparation include Unacademy, BYJU's, and Testbook. These platforms offer a wide array of resources, including video lectures, quizzes, and personalized mentoring. Coursera and edX also feature courses relevant to general studies and current affairs, aiding aspirants in gaining knowledge from renowned institutions. Additionally, many channels on YouTube provide free content, discussing strategies and tips for exam success. These platforms not only help in content learning but also in understanding exam patterns and effective preparation strategies.