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Swup A11y Plugin

A swup plugin for enhanced accessibility.

Loading new content via AJAX is a great experience for most users, but comes with serious shortcomings for screen reader users. This plugin will improve that:

  • Announce page visits to screenreaders by reading the new page title
  • Restore focus after swapping out the content
  • Skip animations for users with a preference for reduced motion

Accessibility can be hard to get right. That's why we're keen to hear your feedback. Share your experience and suggest improvements by opening an issue on this repo. Let's make swup better together!

Installation

Install the plugin from npm and import it into your bundle.

npm install @swup/a11y-plugin
import SwupA11yPlugin from '@swup/a11y-plugin';

Or include the minified production file from a CDN:

<script src="https://unpkg.com/@swup/a11y-plugin@5"></script>

Usage

To run this plugin, include an instance in the swup options.

const swup = new Swup({
  plugins: [new SwupA11yPlugin()]
});

Markup

The plugin should work out of the box if you use proper semantic markup for your content, i.e. a descriptive h1 for each page heading. See the options below for customizing what tags to look for.

<body> <!-- will be focused -->
  <header>
    Logo
  </header>
  <main>
    <h1>Page Title</h1> <!-- will be announced -->
    <p>Lorem ipsum dolor sit amet</p>
  </main>
</body>

Announcements

The plugin will announce the new page to screen readers after navigating to it. It will look for the following and announce the first one found:

  • Heading label: <h1 aria-label="About"></h1>
  • Heading content: <h1>About</h1>
  • Document title: <title>About</title>
  • Page URL: /about/

The easiest way to announce a page title differing from the main heading is using aria-label. The example below will be announced as Homepage.

<h1 aria-label="Homepage">Project Title</h1>

Focus

On page navigation, the plugin will reset focus to the body, imitating default browser behavior. When clicking anchor links on the same page, the plugin will focus the target of the link.

Tip

When linking to other sections on the page, make sure to target a single item that is descriptive of the section, e.g. a heading or a button. Linking to a large container has multiple issues: Some browsers will scroll to the center of the targeted container, disorienting near-sighted users with increased zoom. Screen readers will also start reading out the content of the targeted element, which can be overwhelming when a whole content section is being read out.

Styling

Browsers will display a visible outline around elements focused by this plugin. That's great for orientation of keyboard users, but tends to be annoying for mouse users. We can make both groups of users happy by using a combination of the :focus and :focus-visible pseudo-class to hide any focus outlines while the site is being used with a mouse:

:focus:not(:focus-visible) {
  outline: none;
}

See these guides on Controlling focus and Styling focus for details and more examples.

Options

All options with their default values:

{
  headingSelector: 'h1',
  respectReducedMotion: true,
  autofocus: false,
  announcements: {
    visit: 'Navigated to: {title}',
    url: 'New page at {url}'
  }
}

headingSelector

The selector for finding page headings. The content of the first found heading will be read to screenreaders after a new page was loaded.

respectReducedMotion

Whether to respects users' preference for reduced motion.

Disable animated page transitions and animated scrolling if a user has enabled a setting on their device to minimize the amount of non-essential motion. Learn more about prefers-reduced-motion.

autofocus

Whether to focus elements with an autofocus attribute after navigation.

Caution

Make sure to use this wisely. Automatically focussing elements can be useful to draw attention to inputs, but it comes with a list of drawbacks on its own, especially for screen-reading technology. See Autofocus accessibility considerations for details.

announcements

How the new page is announced. A visit is announced differently depending on whether the new page has a title or not. If found, the main heading or document title is announced. If neither is found, the new url will be announced instead:

  • Title found? Read announcements.visit, replacing {title} with the new title
  • No title? Read announcements.visit too, but replacing {title} with the content of announcements.url
{
  announcements: {
    visit: 'Navigated to: {title}',
    url: 'New page at {url}'
  }
}

Translations

For multi-language sites, pass in a nested object keyed by locale. The locale must match the html element's lang attribute exactly. Use an asterisk * to declare fallback translations.

Note

Swup will not update the lang attribute on its own. For that, you can either install the Head Plugin to do it automatically, or you can do update it yourself in the content:replace hook.

{
  announcements: {
    'en-US': {
      visit: 'Navigated to: {title}',
      url: 'New page at {url}'
    },
    'de-DE': {
      visit: 'Navigiert zu: {title}',
      url: 'Neue Seite unter {url}'
    },
    'fr-FR': {
      visit: 'Navigué vers : {title}',
      url: 'Nouvelle page à {url}'
    },
    '*': {
      visit: '{title}',
      url: '{url}'
    }
  }
}

Visit object

The plugin extends the visit object with a new a11y key that can be used to customize the behavior on the fly.

{
  from: { ... },
  to: { ... },
  a11y: {
    announce: 'Navigated to: About',
    focus: 'body'
  }
}

visit.a11y.announce

The text to announce after the new page was loaded. This is the final text after choosing the correct language from the announcements option and filling in any placeholders. Modify it to read a custom announcement.

Since the text can only be populated once the new page was fetched and its contents are available, the only place to inspect or modify this would be right before the content:announce hook.

swup.hooks.before('content:announce', (visit) => {
  visit.a11y.announce = 'New page loaded';
});

visit.a11y.focus

The element to receive focus after the new page was loaded, by default the body. Can be customized per visit. Set it to a selector string to select an element, or set it to false to not move the focus on this visit.

Hooks

The plugin adds two new hooks: content:announce and content:focus. Both run directly after the internal content:replace handler, when the new content is already in the DOM.

content:announce

Executes the announcement of the new page title.

swup.hooks.on('content:announce', () => console.log('New content was announced'));

content:focus

Executes the focussing of the new page.

swup.hooks.on('content:focus', () => console.log('New content received focus'));

Methods on the swup instance

The plugin adds the following method to the swup instance:

announce

Announce something programmatically. Use this if you are making use of options.resolveUrl and still want state changes to be announced.

swup.announce?.(`Filtered by ${myFilterString}`);