Fluent UI Web Components

Microsoft's Fluent UI Web Components is designed to help you build web apps using Web Components styled with the Fluent design language.

Installation

Install

Fluent UI should be installed as a dependency of your app.

Yarn

yarn add @fluentui/web-components@beta

NPM

npm i @fluentui/web-components@beta

pnpm

pnpm add @fluentui/web-components@beta

From CDN

A pre-bundled script that contains all APIs needed to use FAST Foundation is available on CDN. You can use this script by adding type="module" to the script element and then importing from the CDN.

<!DOCTYPE html>
<html lang="en">
  <head>
    <script type="module" src="https://unpkg.com/@fluentui/web-components@beta"></script>
  </head>
  <!-- ... -->
</html>

The above CDN location points to the latest Beta release of @fluentui/web-components. It is advised that when you deploy your site or app, you import the specific version you have developed and tested with.

For simplicity, examples throughout the documentation will assume the library has been installed from NPM, but you can always replace the import location with the CDN URL.

Setup

Fluent UI Web Components are styled using tokens in the form of CSS variables. You can use the setTheme utility to provide a theme for your website or application.

import { setTheme } from '@fluentui/web-components';
import { webLightTheme } from '@fluentui/tokens';

setTheme(webLightTheme);

Usage

That's it. You can now use Fluent UI Web Components in your app.

Importing the defined component:

import '@fluentui/web-components/button.js';

Defining the element yourself using named imports:

import { ButtonDefinition, FluentDesignSystem } from '@fluentui/web-components';

ButtonDefinition.define(FluentDesignSystem.registry);

Developer Experience

For convenience we have included a CEM (custom elements manifest) at the root of the project.

import CEM from '@fluentui/custom-elements.json' with { type: 'json' };

Development

To start the component development environment, run yarn start.

Known issue with Storybook site hot-reloading during development

Storybook will watch modules for changes and hot-reload the module when necessary. This is usually great but poses a problem when the module being hot-reloaded defines a custom element. A custom element name can only be defined by the CustomElementsRegistry once, so reloading a module that defines a custom element will attempt to re-register the custom element name, throwing an error because the name has already been defined. This error will manifest with the following message: Failed to execute 'define' on 'CustomElementRegistry': the name "my-custom-element-name" has already been used with this registry

This is a known issue and will indicate that you need to refresh the page. We're working on surfacing a more instructive error message for this case.

Testing

On CI, a static test harness build is first generated by running Vite in build mode. The Playwright tests are then run against the generated harness. To run Playwright tests in this mode, use the command yarn nx run web-components:e2e.

To run Playwright tests locally in UI mode, use the command yarn nx run web-components:e2e:local. This will start a local development server with Vite and open the Playwright test runner UI.