Capyloon is an experimental, Web-based user agent and operating system built on and extending b2gOS (Boot to Gecko, the foundation of Firefox OS). It aims to provide users with privacy and control by liberating them from the limitations imposed by traditional OS vendors and service providers. Capyloon leverages the Web as an application platform, offering unique capabilities to manage online activity on the user's terms. The project explores decentralized web technologies like IPFS for content addressing and storage, and privacy-respecting Web Assembly plugins to process data locally. It focuses on creating an open ecosystem for content creators and plugin developers, with a strong emphasis on user agency and data portability.