Top online course marketplaces include Udemy, Coursera, edX, Skillshare, LinkedIn Learning, Udacity, Teachable, Thinkific, Kajabi, and LearnWorlds. They differ in features such as course creation tools, audience reach, revenue-sharing models, certification options, payment processing, learner engagement, and platform security. Udemy and Skillshare are ideal for creators seeking large built-in audiences, while Coursera and edX focus on university-backed certifications and professional credentials. Teachable, Thinkific, and Kajabi offer more control over branding, pricing, and customer relationships for independent educators and businesses. Overall, these platforms vary in monetization flexibility, scalability, security, customization, and learner experience, helping educators and organizations deliver and monetize digital learning at scale.