Udacity is described as 'Provides university-level technical courses online with self-paced, interactive project-based learning, industry collaboration, mentorship, and certificates' and is a popular online education service in the education & reference category. There are more than 100 alternatives to Udacity, not only websites but also apps for a variety of platforms, including iPhone, Android, iPad and Android Tablet apps. The best Udacity alternative is Khan Academy, which is free. Other great sites and apps similar to Udacity are Coursera, Udemy, edX and Wikiversity.