synchtube is described as 'Create public and private rooms and share music, videos, and more, synchronized! Turn your room into a automated TV station, 24/7 radio station, or a simple hangout!' and is a Video Sharing Tool in the Audio & Music category. There are three alternatives to synchtube, not only websites but also apps for a variety of platforms, including Windows, Firefox, Google Chrome and Linux. The best alternative is CyTube, which is both free and Open Source. Other great sites and apps similar to synchtube are Watch2Gether (Freemium) and &chill (Free).
Watch2Gether lets groups of users watch videos in-sync together. At the same time users can communicate through a build-in chat-room and use web cam and audio chat. Available media sources are Youtube, Vimeo, Dailymotion and Soundcloud.