Emotion CSS-in-JS Library

Emotion is a free and open-source, performant and flexible CSS-in-JS library for React and vanilla JavaScript. Created by Kye Hohenberger (tkh44) in 2017, Emotion is designed as a high-performance alternative to Styled Components with additional API flexibility. Used by System UI, Theme UI, and many production applications. Key features: multiple APIs: supports both the css prop (string or object styles) and styled component API (similar to styled-components), giving developers choice. Object styles: styles can be written as JavaScript objects (css({ color: 'blue', fontSize: 14 })) which are faster to evaluate than string parsing. String styles: supports tagged template literals like styled-components for familiar syntax. Theming: ThemeProvider with useTheme hook and responsive design patterns. Performance: Emotion caches serialized styles and avoids unnecessary re-renders. The css function returns a class name, enabling style composition without runtime overhead. SSR: server-side rendering with critical CSS extraction. Labels: debug labels for development tooling. Keyframes and global styles: @emotion/core exports keyframes and Global components. Composition: styles can be composed and combined (compose, css variables). Source maps: accurate source maps for debugging. Framework-agnostic core (@emotion/css) and React-specific package (@emotion/react). JavaScript/TypeScript. MIT.