United States Web Design System

The United States Web Design System includes a library of open source UI components and a visual style guide for U.S. federal government websites.

This repository is for the design system code itself. We maintain another repository for the documentation and website. To see the design system and its documentation on the web, visit https://designsystem.digital.gov.

United States Web Design System

Background

USWDS components and style guide follow industry-standard accessibility guidelines and use the best practices of existing style libraries and modern web design. The U.S. Digital Service and 18F created USWDS for designers and developers. USWDS is a project of GSA’s Technology Transformation Service, maintained by the Office of Products and Programs. They are designed for use by government product teams who want to create beautiful, easy-to-use online experiences for the public. To learn more about the project, check out this blog post and to view websites and applications check out our list here.

Recent updates

Information about the most recent release of the design system can always be found in the release history. We include details about significant updates and any backwards incompatible changes along with a list of all changes.

Getting started

We’re glad you’d like to use the design system — here’s how you can get started:

Using the design system

How you implement the design system depends on the needs of your project and your workstyle. We recommend implementing the design system with npm, but we also provide a direct download if npm will not work for you or your project.

Download the design system if you are not familiar with npm and package management.
Use the design system npm package if you are familiar with using npm and package management.

Download and install

Download the USWDS zip file from the latest USWDS release and open that file.

After extracting the zip file you should see the following file and folder structure:
```
uswds-2.12.2/
├── css/
│   ├── uswds.min.css.map
│   ├── uswds.min.css
│   └── uswds.css
├── fonts/
├── img/
├── js/
│   ├── uswds-init.js
│   ├── uswds-init.min.js
│   ├── uswds-init.min.js.map
│   ├── uswds.min.js.map
│   ├── uswds.min.js
│   └── uswds.js
└── scss/
```
The three files critical to any USWDS project are the stylesheet, the library, and the intializer. Any project requires both the stylesheet and library to function properly.

Stylesheet: This is the compiled CSS stylesheet that describes how design system components look. Reference either uswds.css or uswds.min.css in the <head> of your document.

Library: This is the compiled JavaScript that controls component interactivity. Reference either uswds.js or uswds.min.js at the end of the <body> of your document.

Initializer: This small JavaScript file (less than 1 KB minified) helps the browser know if the USWDS JavaScript library is loading properly. This prevents component content from "flashing" or "shifting" while the page loads. Reference uswds-init.min.js in the <head> of your page, or inline its contents directly into the <script> tag.
Copy these files and folders into a relevant place in your project's code base. Here is an example structure for how this might look:
```
example-project/
├── assets/
│   ├── uswds-2.12.2/
│   ├── stylesheets/
│   ├── images/
│   └── javascript/
└── index.html
```
You'll notice in our example above that we also outline a stylesheets, images and javascript folder in your assets folder. These folders are to help organize any assets that are unique to your project and separate from the design system assets.

Reference the stylesheet, library, and initializer in each HTML page or dynamic template in your project. We also provide Sass (.scss) files in the zip package which you should use to generate new CSS with project-specific settings. See Sass and theme settings for more information.

Here is an example of how to reference these assets in your index.html file:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <title>My Example Project</title>
    <script src="assets/uswds-2.12.2/js/uswds-init.min.js"></script>
    <link rel="stylesheet" href="assets/uswds-2.12.2/css/uswds.min.css" />
  </head>
  <body>
    <script src="assets/uswds-2.12.2/js/uswds.min.js"></script>
  </body>
</html>

We offer both the CSS and the JavaScript in two versions — minified and un-minified. (In the examples above, we are using the minified files.) Use the minified files in a production environment or to reduce the file size of your downloaded assets. Use the un-minified files if you are in a development environment or would like to debug the CSS or JavaScript assets in the browser.

And that’s it — you should now be able to copy our code samples into your index.html and start using the design system.

Install using npm

npm is a package manager for Node-based projects. USWDS maintains a uswds package that includes both the pre-compiled and compiled files — just like the direct download. npm packages make it easy to update and install the design system from the command line.

Install Node/npm. Below is a link to find the install method that coincides with your operating system:
- Node v12.13.0 (current LTS), Installation guides
Note for Windows users: If you are using Windows and are unfamiliar with Node or npm, we recommend following Team Treehouse's tutorial for more information.

Make sure you have installed it correctly:

npm -v
6.13.0 # This line may vary depending on what version of Node you've installed.

Create a package.json file. You can do this manually, but an easier method is to use the npm init command. This command will prompt you with a few questions to create your package.json file.
Add uswds to your project’s package.json:
```
npm install --save uswds@latest
```

The uswds module is now installed as a dependency. You can use the un-compiled files found in the node_modules/uswds/dist/ directory.

node_modules/uswds/
├── dist/
│   ├── css/
│   ├── fonts/
│   ├── img/
│   ├── js/
│   └── scss/

Note: We do not recommend directly editing the design system files in node_modules. One of the benefits of using a package manager is its ease of upgrade and installation. If you make customizations to the files in the package, any upgrade or re-installation will wipe them out.

Using the USWDS package

If you want to take full advantage of USWDS custom settings and add build new styles and components with the USWDS toolset, you'll need a way to access the assets in the USWDS package and compile custom CSS from the USWDS source files.

USWDS uses the task manager Gulp as a way to add USWDS assets to a project and compile our CSS from the package source. Gulp is a useful and powerful tool, but it can be difficult to set up if you are new to it.

The uswds-gulp repo is made for developers new to Gulp or those who just want a simple setup to get started quickly. The repo contains files and instructions for installing Gulp 4.0 in your project, initializing USWDS, and compiling CSS from the source files.

Sass and theme settings

The design system is customizable using the power of Sass (Syntactically Awesome Style Sheets). The critical files you'll need in your project are those in dist/scss/theme:

scss
├── components/
├── core/
├── elements/
├── lib/
├── packages/
├── settings/
├── theme/
│   ├── _uswds-theme-color.scss
│   ├── _uswds-theme-components.scss
│   ├── _uswds-theme-custom-styles.scss
│   ├── _uswds-theme-general.scss
│   ├── _uswds-theme-spacing.scss
│   ├── _uswds-theme-typography.scss
│   ├── _uswds-theme-utilities.scss
│   ├── styles.scss

_uswds-theme-color.scss: theme color settings
_uswds-theme-components.scss: theme component settings
_uswds-theme-custom-styles.scss: additional project CSS for customizing or adding to what USWDS provides
_uswds-theme-general.scss: General theme settings
_uswds-theme-spacing.scss: Theme spacing settings
_uswds-theme-typography.scss: Theme typography settings
_uswds-theme-utilities.scss: Utility class output settings
styles.scss: The primary Sass file that you'll compile. It collects theme settings, USWDS source files, and custom CSS

styles.scss looks something like the following code. It adds all the project theme settings, then adds USWDS source, and finally adds your project's custom styles:

@import "uswds-theme-general";
@import "uswds-theme-typography";
@import "uswds-theme-spacing";
@import "uswds-theme-color";
@import "uswds-theme-utilities";
@import "uswds";
@import "uswds-theme-custom-styles";

Technical note: The @import 'uswds' statement above needs to reference the uswds.scss file in node_modules/uswds/dist/scss. The gulpfile in uswds-gulp is set up to do this automatically, using gulp-sass and includePaths.

Sass compilation requirements

The design system requires autoprefixing to work properly. This is included in the uswds-gulp package.

Autoprefixing uses a service like gulp-autoprefixer to automatically add vendor prefixes to the precompiled stylesheets. Don't add vendor prefixes to your custom styles manually — it is more reliable to use autoprefixing. We use the following autoprefixer settings via .browserslistrc config:

> 2%
last 2 versions
IE 11
not dead

Note: media query sorting is no longer required as of USWDS 2.5.0. We stopped sorting media queries with csso in USWDS 2.5.1 because it wasn't outputting as expected. While both the minified and unminified CSS files are modestly larger as a result: 268 KB unsorted vs. 259 KB sorted, our testing indicates that once the files are compressed server side with gzip, the unsorted CSS is actually smaller: 36 KB unsorted and gzipped vs. 38 KB sorted and gzipped. As a result, we recommend that teams do not use media query sorting at this time.

We recommend using a minifier like csso to compress your final compiled CSS and sourcemaps like gulp-sourcemaps to keep track of the location of all the source Sass for easier debugging.

JavaScript

require('uswds') will load all of USWDS’s JavaScript onto the page. Add this line to whatever initializer you use to load JavaScript into your application.

Use another framework or package manager

If you’re using another framework or package manager that doesn’t support npm, you can find the source files in this repository and use them in your project. Otherwise, we recommend that you follow the download instructions. Please note that the core team isn’t responsible for all frameworks’ implementations.

If you’re interested in maintaining a package that helps us distribute USWDS, the project’s build system can help you create distribution bundles to use in your project. Please read our contributing guidelines to locally build distributions for your framework or package manager.

CSS architecture

The CSS foundation of this site is built with the Sass preprocessor language.
The CSS organization and naming conventions follow 18F’s Front End Guide.
We format our code with Prettier, per the formatting section of the 18F Front End Guide.
CSS selectors are prefixed with usa (For example: .usa-button). This identifier helps the design system avoid conflicts with other styles on a site which are not part of USWDS.
Uses a BEM approach for naming CSS selectors. Blocks are separated from elements with two underscores (__). Multi-word blocks use single hyphens instead of spaces. Modifier classes are additive — proper markup requires the base class and the modifier class or classes. Modifier classes consist of the base class plus a modifier suffix, separated by two hyphens (--) as in .usa-button.usa-button--secondary or usa-accordion.usa-accordion--bordered.
Uses modular CSS for scalable, modular, and flexible code.
Uses nesting when appropriate. Nest minimally with up to two levels of nesting.
Hard-coded magic numbers are avoided.
Media queries are built mobile first.
Spacing units are set with the units() function as described in the USWDS 2.0 documentation. In general, we use spacing in multiples of 8px — expressed as a multiple in units([multiple]). For instance units(2) is the equivalent of 2 * 8px or 16px. In the final, compiled CSS, this value will be expressed in rem, as a multiple of the base font size set with $theme-base-font-size.

For more information, visit: 18F’s CSS Front End Guide

JS customization

Unfortunately, customizing the JavaScript for the USWDS currently requires NodeJS and a module bundler like Browserify or Webpack. We apologize for this inconvenience, and are working to resolve it in a future release of the design system.

USWDS JavaScript is separated into components (just as with the CSS and HTML) and initialized with event handlers when the DOM is ready. These components are accessible as CommonJS modules that can be required in other JavaScript files, then built for the browser. The components are not accessible in the global browser scope, but can be extended to be included by requiring components and setting it to a global scope:

window.uswds = require("./components");

Each component has a standardized interface that can be used to extend it further. The components store a HTML class (like .usa-accordion__button[aria-controls]) used to link HTML elements with the JavaScript component. When a component is initialized, it searches through the current HTML DOM to find all elements that match the class and initializes the component JavaScript for those elements. The primary methods for each component include:

on: Initialize a component's JavaScript behavior by passing the root element, such as window.document.
off: The opposite of on, de-initializes a component, removing any JavaScript event handlers on the component.
hide: Hide the whole component.
show: Shows a whole, hidden component.
toggle: Toggles the visibility of a component on and off based on the previous state.

Some components have additional methods based on that component's functionality. Any additional methods are found in that component's JavaScript file.

If you’re using a modern framework like React or Angular you can import components and initialize them in your library's DOM ready lifecycle event.

Importing a modular component.

import USWDS from "../node_modules/uswds/src/js/components";
const { characterCount, accordion } = USWDS; // deconstruct your components here

React hooks example:

function App() {
  const ref = document.body;

  useEffect(() => {
    // initialize
    characterCount.on(ref);
    // default ref is document.body, if you want to use
    // default you do not have to pass arguments
    accordion.on();

    // remove event listeners when component un-mounts.
    return () => {
      characterCount.off();
      accordion.off();
    };
  });
}

Angular example:

export class App implements OnInit {
  constructor() {
    this.ref = document.body;
    // default ref is document.body, if you want to use
    // default you do not have to pass arguments
  }

  ngOnInit() {
    // initialize
    characterCount.on(this.ref);
    accordion.on();
  }

  // remove event listeners when component un-mounts.
  ngOnDestroy() {
    characterCount.off();
    accordion.off();
  }
}

Those using Webpack 5 can take advantage of the updated exports field which allows declaration for requests like import "uswds" or import accordion from "uswds/src/js/components/accordion"

Customization, theming, and tokens

USWDS 2.0 provides extensive support for theming via its theme settings files introduced in Sass and theme settings, above.

Set theme settings with USWDS design tokens, not with values directly. They tend to be quoted strings like 'desktop' or 'md' or unitless numbers like 2 or -1.5. Tokens are the values passed into the USWDS functions and mixins that parse them. They are the keys that, through the mechanism of a function or mixin, unlock a value — they are not the values themselves.

Visit the Design tokens section of USWDS 2.0 documentation for more on the available tokens for color, spacing units, font size, and more.

Using tokens in theme settings

The following is an example of theme settings from _uswds-theme-spacing.scss:

$theme-site-max-width: "desktop";
$theme-site-margins-breakpoint: "desktop";
$theme-site-margins-width: 4;
$theme-site-margins-mobile-width: 2;

The USWDS uses those tokens to build component styles:

.usa-example {
  @include u-padding-x($theme-site-margins-mobile-width);
  max-width: units($theme-site-max-width);

  @include at-media($theme-site-margins-breakpoint) {
    @include u-padding-x($theme-site-margins-width);
  }
}

This is the functional equivalent of:

.usa-example {
  @include u-padding-x(2);
  max-width: units("desktop");

  @include at-media("desktop") {
    @include u-padding-x(4);
  }
}

Which, if $theme-respect-user-font-size is set to true would output something like:

.usa-example {
  padding-left: 1rem;
  padding-right: 1rem;
  max-width: 64rem;
}

@media screen and (min-width: 64em) {
  .usa-example {
    padding-left: 2rem;
    padding-right: 2rem;
  }
}

In general, USWDS sets variables with tokens, and passes those variables into functions and mixins in the source Sass.

Set the base asset paths (fonts and images)

The values of $theme-font-path and $theme-image-path will be appended to USWDS font paths and image paths, respectively:

$theme-font-path:   '../fonts';
$theme-image-path:  '../img';

Where things live

HTML markup for the components is located in: src/components in the site root. These, however, are written in the templating language Nunjucks. It's best to get HTML source markup directly from designsystem.digital.gov/components
Sass stylesheets are located in: dist/scss/ (/core, /elements, /components). Compiled CSS is located in the downloadable zip file.
JS is located in: src/js (/components, /utils).
Fonts are located in: dist/fonts.
Images and icons are located in: dist/img.

Browser support

We’ve designed the design system to support older and newer browsers through progressive enhancement. The current major version of the design system (2.0) follows the 2% rule: we officially support any browser above 2% usage as observed by analytics.usa.gov. Currently, this means that the design system version 2.0 supports the newest versions of Chrome, Firefox, Safari, and Internet Explorer 11 and up.

Accessibility

The design system also meets the WCAG 2.0 AA accessibility guidelines and conforms to the standards of Section 508 of the Rehabilitation Act. We’re happy to answer questions about accessibility — email us for more information.

Fractal

We're using Fractal to generate an interactive component library for the design system. You can run it locally after npm install with:

npm start

Then, visit http://localhost:3000/ to see the design system in action.

Optional: To re-build when code changes are made, run the following command from the project directory in a separate terminal window:

npm run watch

Template compatibility

Many of our Fractal view templates are compatible with Nunjucks (for JavaScript/Node), Jinja (Python), and Twig (PHP) out of the box. Components that reference other components use a Fractal-specific {% render %} tag that will either need to be implemented in other environments or replaced with the appropriate {% include %} tags.

Long-term support of v1.x

Version 1.x is in maintenance mode. We will only make critical updates like security patches.

Need installation help?

Do you have questions or need help with setup? Did you run into any weird errors while following these instructions? Feel free to open an issue here:

https://github.com/uswds/uswds/issues.

You can also email us directly at uswds@gsa.gov.

Contributing to the code base

For complete instructions on how to contribute code, please read CONTRIBUTING.md. These instructions also include guidance on how to set up your own copy of the design system style guide website for development.

If you would like to learn more about our workflow process, check out the Workflow and Issue label Glossary pages on the wiki.

If you have questions or concerns about our contributing workflow, please contact us by filing a GitHub issue or emailing our team.

Reuse of open-source style guides

Much of the guidance in USWDS leans on open source designs, code, and patterns from other civic and government organizations, including:

Consumer Financial Protection Bureau’s Design Manual
U.S. Patent and Trademark Office’s Design Patterns
Healthcare.gov Style Guide
UK’s Government Digital Service’s UI Elements
Code for America’s Chime Styleguide
Pivotal Labs Component Library

Licenses and attribution

A few parts of this project are not in the public domain. Attribution and licensing information for those parts are described in detail in LICENSE.md.

The rest of this project is in the worldwide public domain, released under the CC0 1.0 Universal public domain dedication.

Contributing

All contributions to this project will be released under the CC0 dedication alongside the public domain portions of this project. For more information, see CONTRIBUTING.md.

wendellpiez/uswds