Cardstack is a composable open software ecosystem built on the principles of shared code, data, and revenue. It functions as an experience layer for the decentralized internet, enabling developers to build applications that bridge Web2 and Web3 technologies. The platform provides a full-stack development framework, ready-to-use applications, and tools to integrate with external systems like blockchains and LLMs. A key feature is its on-chain revenue and reward protocol, which automates payouts to contributors and decentralized infrastructure services based on usage analytics. The project, managed by the Cardstack Foundation in Zug, Switzerland, aims to create a sustainable and open alternative to centralized application platforms by giving users control over their data and fostering a community-driven economy powered by the CARD token.