This paper identifies and conceptualizes the role of mobile chat applications (WhatsApp, WeChat, LINE, KakaoTalk, Snapchat, Firechat, Signal, Telegram, and others) as tools of political protest. Drawing on several dozen interviews with activists and journalists in Hong Kong and China, the paper focuses on political activism from 2014-present, emphasizing the significance of chat apps in contexts of surveillance. It explores the ways that mobile-first tools have changed the organization and mobilization of protest movements, as well as the ways that leaders and other participants seek to persuade those outside the movement. The paper also considers the vast amount of content that chat apps have produced (from intra-group chats to communiques aimed at journalists, to memes and art, to photos and clips, to dis- and misinformation) and the ways that news organizations have used chat apps as tools for covering large-scale protests. The paper emphasizes the shift from open social media (e.g. Twitter) to a still-evolving mix of open and closed conversations in chat apps.