Fluent 2 Design System

Build production-grade interfaces using Microsoft’s Fluent 2 design system with @fluentui/react-components (v9).

Quick Start

Every Fluent 2 React app requires a FluentProvider wrapping the component tree with a theme:

import {
  FluentProvider,
  webLightTheme,
  webDarkTheme,
  Button,
  tokens,
  makeStyles,
  mergeClasses,
} from "@fluentui/react-components";

export default function App() {
  return (
    <FluentProvider theme={webLightTheme}>
      <Button appearance="primary">Hello Fluent 2</Button>
    </FluentProvider>
  );
}

Install: npm install @fluentui/react-components

Core Architecture

Theming

• Built-in themes: webLightTheme, webDarkTheme, teamsLightTheme, teamsDarkTheme, teamsHighContrastTheme
• Custom branding: Use createLightTheme(brandRamp) / createDarkTheme(brandRamp) with a BrandVariants object (keys 10–160)
• Nesting: FluentProvider can nest for sub-trees with different themes
• Theme values are emitted as CSS custom properties on the provider element

Styling with Griffel

Use makeStyles (from @fluentui/react-components) — never inline styles or external CSS for token-aware styling.

const useStyles = makeStyles({
  root: {
    backgroundColor: tokens.colorNeutralBackground1,
    color: tokens.colorNeutralForeground1,
    display: "flex",
    gap: tokens.spacingHorizontalM,
    padding: tokens.spacingVerticalM,
  },
  active: {
    backgroundColor: tokens.colorBrandBackground,
    color: tokens.colorNeutralForegroundOnBrand,
  },
});

function MyComponent({ isActive }) {
  const styles = useStyles();
  return (
    <div className={mergeClasses(styles.root, isActive && styles.active)}>
      Content
    </div>
  );
}

Critical rules:

• Define makeStyles outside components (module scope)
• Use mergeClasses() to compose classes — never concatenate strings
• Use tokens.* for all colors, spacing, typography, radii, shadows — never hardcode hex/px values
• CSS shorthands (border, borderRadius, padding, etc.) are not supported — use shorthands.* helper or longhand properties
• Pseudo-selectors use nested objects: ":hover": { color: tokens.colorBrandForeground1 }
• Media queries use nested objects: "@media (min-width: 768px)": { flexDirection: "row" }

Component Model

All v9 components follow a consistent pattern:

• Slots: Named sub-parts (e.g., root, icon, content) that accept props or JSX
• Appearance variants: "primary", "secondary", "subtle", "transparent", "outline"
• Size variants: "small", "medium", "large"
• Shape variants: "rounded", "circular", "square"

Override component styles via className with makeStyles/mergeClasses.

Design Tokens

Tokens are the bridge between design intent and code. Always use tokens.* — never raw values.

For complete token reference tables (color, typography, spacing, elevation, stroke, corner radius), see references/tokens.md.

Token Categories at a Glance

Two-Layer Token System

1. Global tokens — context-agnostic raw values (e.g., colorBlue60, fontSize300)
2. Alias tokens — semantic meaning applied to globals (e.g., colorBrandBackground → blue, colorNeutralForeground1 → dark gray)

In code, consume alias tokens via the tokens object.

Layout

• Grid: Use CSS Grid/Flexbox — Fluent 2 v9 has no Stack component
• Spacing scale: 4px base unit. Values: XXS(2), XS(4), S(8), M(12), L(16), XL(20), XXL(24), XXXL(32)
• Column grid: 12-column framework recommended for web; use CSS grid
• Alignment: Use tokens.spacingHorizontal* and tokens.spacingVertical* for consistent spacing

Typography

• Primary typeface: Segoe UI (web), Segoe UI Variable (Windows), SF Pro (macOS/iOS), Roboto (Android)
• Font stack: tokens.fontFamilyBase = Segoe UI → system fallbacks → sans-serif
• Monospace: tokens.fontFamilyMonospace
• Text presets: Use <Text> component with preset variants — Caption1, Body1, Body1Strong, Subtitle1, Subtitle2, Title1, Title2, Title3, LargeTitle, Display
• Alignment: Left-align for LTR; Fluent handles RTL automatically via Griffel

Color System

Three palettes:

1. Neutral — blacks, whites, grays for surfaces, text, layout
2. Brand — accent colors reinforcing identity (default Microsoft brand = blue)
3. Shared/Status — cross-product colors: red (danger), green (success), yellow (warning), blue (informational)

Interaction states: rest → hover (darker) → pressed (darkest). Focus adds a thicker stroke, not a color change.

Accessibility

• All components include ARIA roles, keyboard navigation (via Tabster), and focus management
• High contrast: use teamsHighContrastTheme or handle @media (forced-colors: active) with system colors (ButtonText, Highlight, etc.)
• Focus indicators are visible by default — never remove them
• Ensure WCAG contrast via semantic token pairing (e.g., colorNeutralForeground1 on colorNeutralBackground1)

Component Inventory

For the full categorized component list with usage notes, see references/components.md.

Most-Used Components

Actions: Button, CompoundButton, SplitButton, ToggleButton, MenuButton, Link Inputs: Input, Textarea, Select, Combobox, Dropdown, Checkbox, RadioGroup, Switch, Slider, SpinButton, DatePicker, TimePicker Layout: Card, Divider, Drawer, Dialog, Popover, Tooltip Data Display: Table, DataGrid, Tree, Accordion, Badge, Avatar, AvatarGroup, Tag, Persona Navigation: TabList, Breadcrumb, Nav (preview) Feedback: Toast, MessageBar, ProgressBar, Spinner, Skeleton Surfaces: Menu, Toolbar, Overflow

Common Patterns

App Shell Layout

const useStyles = makeStyles({
  app: {
    backgroundColor: tokens.colorNeutralBackground1,
    display: "grid",
    gridTemplateColumns: "1fr",
    gridTemplateRows: "auto 1fr auto",
    height: "100vh",
    width: "100%",
  },
  header: {
    borderBottom: `${tokens.strokeWidthThin} solid ${tokens.colorNeutralStroke1}`,
    paddingTop: tokens.spacingVerticalS,
    paddingBottom: tokens.spacingVerticalS,
    paddingLeft: tokens.spacingHorizontalM,
    paddingRight: tokens.spacingHorizontalM,
  },
  content: {
    display: "grid",
    gridTemplateColumns: "280px 1fr",
    overflow: "hidden",
  },
  nav: {
    borderRight: `${tokens.strokeWidthThin} solid ${tokens.colorNeutralStroke1}`,
    overflowY: "auto",
  },
  main: {
    overflowY: "auto",
    paddingLeft: tokens.spacingHorizontalL,
    paddingRight: tokens.spacingHorizontalL,
    paddingTop: tokens.spacingVerticalL,
    paddingBottom: tokens.spacingVerticalL,
  },
});

Custom Brand Theme

import { createLightTheme, createDarkTheme } from "@fluentui/react-components";

const myBrand = {
  10: "#020305", 20: "#111723", 30: "#16263D",
  40: "#193253", 50: "#1B3F6A", 60: "#1B4C82",
  70: "#18599B", 80: "#1267B4", 90: "#3174C2",
  100: "#4F82C8", 110: "#6790CF", 120: "#7F9ED5",
  130: "#96ADDC", 140: "#ADBCE3", 150: "#C4CBE9",
  160: "#DBDBF0",
};

const lightTheme = createLightTheme(myBrand);
const darkTheme = createDarkTheme(myBrand);

Dark Mode Toggle

function App() {
  const [isDark, setIsDark] = useState(false);
  return (
    <FluentProvider theme={isDark ? webDarkTheme : webLightTheme}>
      <Switch
        label="Dark mode"
        checked={isDark}
        onChange={(_, data) => setIsDark(data.checked)}
      />
    </FluentProvider>
  );
}

Anti-Patterns

• ❌ Hardcoded colors (color: "#333") — use tokens.colorNeutralForeground1
• ❌ CSS shorthand properties in makeStyles (border: "1px solid red") — use longhand or shorthands.*
• ❌ String concatenation of classNames — use mergeClasses()
• ❌ Inline style props for token-based values — use makeStyles with tokens
• ❌ Importing from @fluentui/react (v8) in v9 projects — use @fluentui/react-components
• ❌ Using v8 Stack — use CSS Grid or Flexbox
• ❌ Overriding CSS custom properties from the color system directly in CSS — the adaptive color system is JS-driven
• ❌ Removing focus indicators — accessibility requirement