Styled System
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Styled System is a low-level, framework-agnostic suite of utilities. It can be used with many different libraries, including React, Vue.js, Angular, Styled Components, Emotion, JSS, and more. While Styled System will always remain fairly low-level, there are many other libraries built on top of the core concepts and functionality included in this library.

If you're looking for a framework-agnostic utility for managing design constraints and scales within a design system, and want to build custom components with a consistent learn-once-use-anywhere API, Styled System is a perfect choice.

If you're looking for something more batteries-included or something off-the-shelf that you can start using today, consider the following libraries, which are built on top of the core Styled System.


Rebass is a themeable primitive UI component library for React, built with Emotion, Styled Components, and Styled System. Since it is built with Styled System, any theme object created for Styled System should work with Rebass. Rebass components include a consistent style props API, and can be used to build out larger component libraries.

Rebass is completely themeable and includes a flexible variants API. Rebass is intended to serve as base components that you can extend to create custom component libraries and design systems. Rebass is also an excellent choice for building out prototypes and UI without needing to invest time in building a custom design system up-front. Rebass components can be used standalone or with apps built with Theme UI.


Reflexbox is the core Box and Flex layout components used to build Rebass. If you're looking for best-in-class developer ergonomics for handling flexbox layout, but don't need the additional components included in Rebass, this package is for you.

Theme UI

Theme UI is a batteries-included library, that's intended for creating themeable component libraries, apps, sites, and Gatsby themes. Theme UI is built with Styled System, Emotion, and MDX. It includes plugins and integrations for Gatsby, Typography.js, Prism, and more. Theme UI has first-class support for styling MDX and markdown content, and it also includes additional features like color modes and a growing library of theme presets. Use Theme UI if you're looking for a complete but flexible styling solution with theme-based design-constraints and developer ergonomics.

Theme Specification

The Theme Specification drives all the theming concepts used throughout these libraries. By conforming to this standard, theme objects created with any of the libraries above will work with the other libraries.

Other Community Libraries

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Theme Specification