This study investigates how COVID-19-related content, especially conspiracy theories, is communicated on “dark platforms” — digital platforms that are less regulated and moderated, hence can be used for hosting content and content creators that may not be tolerated by their more mainstream counterparts. The objective of this study is two-fold: First, it introduces the concept of dark platforms, which differ from their mainstream counterparts in terms of content governance, user-base and technological infrastructure. Second, using 8kun and Gab as examples, this study investigates how the ongoing COVID-19 pandemic has been communicated on dark platforms, with a focus on conspiracy theories. Over 60,000 COVID-19-related posts were studied to identify the most prominent conspiracy theories, their themes, and the actors who promoted them, as well as the broader information ecosystem through network analysis. While pressure on social media to deplatform conspiracy theorists continues to grow, we argue that more research needs to be done to critically investigate the impacts of further marginalizing such groups. To this end, the concept of dark platform as can serve as a heuristic device for researching a wider range of fringe platforms.