MacKinnon is a journalist, free speech activist, and expert on Internet censorship. She spent her childhood in Berkeley, Delhi, Hong Kong, and Beijing. Fluent in Mandarin Chinese, MacKinnon worked for CNN in northeast Asia for over a decade, serving as Beijing bureau chief and correspondent from 1998 to 2001, and Tokyo bureau chief and correspondent from 2001 to 2003. She has also covered major news events in North and South Korea, Pakistan, and the Philippines. After leaving CNN in 2004, she spent three years as a research fellow at Harvard in the Kennedy School's Shorenstein Center on Press and Public Policy and the Law School's Berkman Center for Internet and Society.

In 2004, MacKinnon co-founded Global Voices Online, a community of more than 500 bloggers and translators around the world who work together to disseminate reports from blogs and citizen media everywhere, with an emphasis on voices that are not ordinarily heard in mainstream media. The site is translated into more than 30 languages and provides a forum for individuals and groups in censored communities to spread their messages. MacKinnon is also a founding member of the Global Network Initiative, a global corporate code of conduct for free expression and privacy. From 2007 to 2008, she served as public lead for Creative Commons Hong Kong.

MacKinnon is the author of Consent of the Networked: The Worldwide Struggle for Internet Freedom, which seeks to address the urgent question of how technology should be structured and governed to support the rights and liberties of Internet users worldwide. MacKinnon offers a framework for concerned citizens to understand the complex and often hidden power dynamics among governments, corporations, and citizens in cyberspace. She warns that a convergence of unchecked government actions and unaccountable company practices threatens the future of democracy and human rights around the world.