Storybook is the open-source documentation + development environment for UI components. Each component renders in isolation across all variants + states, enabling visual review, accessibility testing, visual regression detection, and consumer documentation.
For design systems + component libraries, Storybook is the de-facto standard. Used by Airbnb, Shopify, Google, IBM, and most modern design systems.
Beyond documentation, Storybook integrates with: Chromatic for visual regression testing, MSW for API mocking in component stories, Pa11y + axe for accessibility testing. The full Storybook + Chromatic + MSW stack is the modern frontend dev environment.