In this report, we present technical experiments which reveal that WeChat communications that are conducted entirely among non-China-registered accounts are subject to content surveillance. We found that documents and images that were transmitted entirely among non-China-registered accounts were analyzed for Chinese political sensitivity. Upon analysis, files deemed politically sensitive were used to invisibly train and build up WeChat’s Chinese political censorship system. We also conducted analysis of WeChat’s public-facing policy documents, made data access requests, and engaged with Tencent data protection representatives to assess whether those methods could also explain, or uncover, the content surveillance carried out towards international users’ communications. We found that none of the information WeChat makes available to users explains the rationales for such surveillance or the transmission of content hashes from WeChat International to WeChat China.