Created in January 2011 by Tencent Holdings, Weixin, ‘micro message’ in Chinese, was initially a text and voice messaging mobile application. As it expanded, it has transformed and accumulated new functions, to the point that it seems today to be almost indispensable to Chinese society, as evidenced by its extremely high number of users. The international version of Weixin, WeChat, was launched in April 2012 in the context of the global expansion and strengthening of the enterprise. Weixin/WeChat has in fact built its own complex, dense and localised model, which is very different from its so-called Western counterparts. Through an analysis of its industrial strategy and functionalities, this chapter proposes to discuss the scale and complexity of China’s most important communication tool, by explaining its structuring role in society, and by doing so, aims to contribute to better understanding its expansion, experimentation and current limitations. It will, first, return to the historical conditions of the diversification of the services offered by Weixin and will, then, analyse their main socio-technical and socio-economic characteristics before, finally, describing its internationalisation strategies and their difficulties.