Theme UI

The Design Graph Framework

Theme UI is a library for creating themeable user interfaces based on constraint-based design principles. Build custom component libraries, design systems, web applications, Gatsby themes, and more with a flexible API for best-in-class developer ergonomics.

https://theme-ui.com

Built for design systems, white-labels, themes, and other applications where customizing colors, typography, and layout are treated as first-class citizens and based on a standard Theme Specification, Theme UI is intended to work in a variety of applications, libraries, and other UI components. Colors, typography, and layout styles derived from customizable theme-based design scales help you build UI rooted in constraint-based design principles.

• The next evolution of Styled System
• From the creators of utility-based, atomic CSS methodologies
• Theme-based styling with the sx prop
• Style MDX content with a simple, expressive API
• Works with Typography.js themes
• Compatible with virtually any UI component library
• Works with existing Styled System components
• Quick mobile-first responsive styles
• Built-in support for dark modes
• Primitive page layout components
• Plugin for use in Gatsby sites and themes
• Completely customizable with robust theming
• Built with a standard Theme Specification for interoperability
• Built with Emotion for scoped styles

Getting Started

npm install theme-ui

Any styles in your app can reference values from the global theme object. To provide the theme in context, wrap your application with the ThemeProvider component and pass in a custom theme object.

// basic usage
import React from 'react'
import { ThemeProvider } from 'theme-ui'
import theme from './theme'

export default props => (
  <ThemeProvider theme={theme}>{props.children}</ThemeProvider>
)

The theme object follows the System UI Theme Specification, which lets you define custom color palettes, typographic scales, fonts, and more. Read more about theming.

// example theme.js
export default {
  fonts: {
    body:
      'system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif',
    heading: '"Avenir Next", sans-serif',
    monospace: 'Menlo, monospace',
  },
  colors: {
    text: '#000',
    background: '#fff',
    primary: '#33e',
  },
}

sx prop

The sx prop works similarly to Emotion's css prop, accepting style objects to add CSS directly to an element in JSX, but includes extra theme-aware functionality. Using the sx prop for styles means that certain properties can reference values defined in your theme object. This is intended to make keeping styles consistent throughout your app the easy thing to do.

The sx prop only works in modules that have defined a custom pragma at the top of the file, which replaces the default React.createElement function. This means you can control which modules in your application opt into this feature without the need for a Babel plugin or additional configuration.

/** @jsx jsx */
import { jsx } from 'theme-ui'

export default props => (
  <div
    sx={{
      fontWeight: 'bold',
      fontSize: 4, // picks up value from `theme.fontSizes[4]`
      color: 'primary', // picks up value from `theme.colors.primary`
    }}>
    Hello
  </div>
)

Read more about how the custom pragma works.

Responsive styles

The sx prop also supports using arrays as values to change properties responsively with a mobile-first approach. This API originated in Styled System and is intended as a terser syntax for applying responsive styles across a singular dimension.

/** @jsx jsx */
import { jsx } from 'theme-ui'

export default props => (
  <div
    sx={{
      // applies width 100% to all viewport widths,
      // width 50% above the first breakpoint,
      // and 25% above the next breakpoint
      width: ['100%', '50%', '25%'],
    }}
  />
)

Documentation

• Theming
• The sx Prop
• Layout
• Color Modes
• Styled
• MDX Components
• Theme Spec
• Gatsby Plugin
• API

MIT License