React Cosmos ranks #10 in Design Systems & Component Libraries AI search.

React Cosmos is an open-source sandbox for developing and testing React UI components in isolation. Originally created in 2015 within Hootsuite's Bucharest Analytics team and first presented at ReactEurope 2015 in Paris, the project has grown to over 8,700 GitHub stars under the stewardship of lead maintainer Ovidiu Cherecheș. It centers on a file-system fixture convention that lets developers define and bookmark component states, a browser-based UI playground for browsing and interacting with those fixtures, and a full-stack plugin system for extensibility. React Cosmos integrates natively with Vite, Webpack, Next.js, and React Native, and can export an interactive static component library to any hosting service. It is MIT-licensed, written entirely in TypeScript, and community-funded through GitHub Sponsors.

React Cosmos is a free, open-source, React-exclusive component sandbox that enables frontend developers to build, test, and iterate on UI components in isolation using a file-system fixture model, an interactive browser UI, and a full-stack plugin system.