wang formally launched tudou online on april 15, 2005, and the website soon took off. tudou started as a website hosting user-generated content (ugc), but soon expanded to include ugc, premium licensed content and content developed in-house, commonly described as a combination of the youtube, hulu, and hbo business models. the number of monthly unique visitors to tudou increased from approximately 50 million in december 2007 to approximately 182 million in december 2010, and to approximately 200 million in may 2011. the number of registered users increased from approximately 35.6 million in december 31, 2008 to approximately 78.2 million as of december 31, 2010 and further to approximately 90.1 million as of june 30, 2011.