As of 2014, he has published twelve books including two New York Times best-selling books. In 2003 he founded and has since directed Jihad Watch, a blog which he describes as containing “news of the international jihad, [and] commentary” which is dedicated to “bringing public attention to the role that jihad theology and ideology plays in the modern world, and to correcting popular misconceptions about the role of jihad and religion in modern-day conflicts”.
He has also co-founded Stop Islamization of America (SIOA) and the Freedom Defense Initiative with blogger Pamela Geller, with whom he also co-authored a book, The Post-American Presidency: The Obama Administration’s War on America. His viewpoints have been described as anti-Islamic or Islamophobic. The UK Home Office has barred Spencer and Geller from travel to the UK for “making statements that may foster hatred that might lead to inter-community violence”.