Abstract: China's Internet filtering regime is the most sophisticated effort of its kind in the world. Compared to similar efforts in other states, China's filtering regime is pervasive, sophisticated, and effective. It comprises multiple levels of legal regulation and technical control. It involves numerous state agencies and thousands of public and private personnel. It censors content transmitted through multiple methods, including Web pages, Web logs, on-line discussion forums, university bulletin board systems, and e-mail messages. Our testing found efforts to prevent access to a wide range of sensitive materials, from pornography to religious material to political dissent. We sought to determine the degree to which China filters sites on topics that the Chinese government finds sensitive, and found that the state does so extensively. Chinese citizens seeking access to Web sites containing content related to Taiwanese and Tibetan independence, Falun Gong, the Dalai Lama, the Tiananmen Square incident, opposition political parties, or a variety of anti-Communist movements will frequently find themselves blocked. Contrary to anecdote, we found that most major American media sites, such as CNN, MSNBC, and ABC, are generally available in China (though the BBC remains blocked). Moreover, most sites we tested in our global list's human rights and anonymizer categories are accessible as well. While it is difficult to describe this widespread filtering with precision, our research documents a system that imposes strong controls on its citizens' ability to view and to publish Internet content. This report was produced by the OpenNet Initiative, a partnership among the Advanced Network Research Group, Cambridge Security Programme at Cambridge University, the Citizen Lab at the Munk Centre for International Studies, University of Toronto, and the Berkman Center for Internet & Society at Harvard Law School.