This study examines how Chinese authorities distinguish between acceptable and unacceptable diplomatic discourse within China’s cyberspace. Using computer-assisted text analysis, we analyze a unique dataset comprising US Embassy social media posts on the Chinese platform Weibo between 2010 and 2020. Our findings challenge prevailing assumptions, revealing a degree of tolerance for posts that promote Western social life, human rights, and liberal democracy. Instead, the focus of the Chinese authorities is to curtail the US Embassy’s public engagement in discussing politically sensitive topics, particularly those related to China’s regime security. We contend that a hierarchical security framework can provide a more thorough understanding of China’s information control practices. This study extends previous research on China’s information control beyond the domestic context and provides a fresh examination of China’s domestic politics and foreign policy. It also highlights the potential and limitations of foreign public diplomacy in China’s cyberspace.