Accessibility

A brief overview of CoreUI for React features and limitations for the creation of accessible content.

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CoreUI for React provides an easy-to-use framework of ready-made styles, layout tools, and interactive components, allowing developers to create websites and applications that are visually appealing, functionally rich, and accessible out of the box.

Overview and limitations

The overall accessibility of any project built with CoreUI for React depends in large part on the author’s markup, additional styling, and scripting they’ve included. However, provided that these have been implemented correctly, it should be perfectly possible to create websites and applications with CoreUI for React that fulfill WCAG 2.1 (A/AA/AAA), Section 508, and similar accessibility standards and requirements.

Structural markup

CoreUI for React styling and layout can be applied to a wide range of markup structures. This documentation aims to provide developers with best practice examples to demonstrate the use of CoreUI for React itself and illustrate appropriate semantic markup, including ways in which potential accessibility concerns can be addressed.

Interactive components

CoreUI for React interactive components—such as modal dialogs, dropdown menus, and custom tooltips—are designed to work for touch, mouse, and keyboard users. Through the use of relevant WAI-ARIA roles and attributes, these components should also be understandable and operable using assistive technologies (such as screen readers).

Because CoreUI for React components are purposely designed to be fairly generic, authors may need to include further ARIA roles and attributes, as well as JavaScript behavior, to more accurately convey the precise nature and functionality of their component. This is usually noted in the documentation.

Color contrast

Some combinations of colors that currently make up CoreUI for React default palette—used throughout the framework for things such as button variations, alert variations, form validation indicators—may lead to insufficient color contrast (below the recommended WCAG 2.1 text color contrast ratio of 4.5:1 and the WCAG 2.1 non-text color contrast ratio of 3:1), particularly when used against a light background. Authors are encouraged to test their specific uses of color and, where necessary, manually modify/extend these default colors to ensure adequate color contrast ratios.

Content which should be visually hidden, but remain accessible to assistive technologies such as screen readers, can be styled using the .visually-hidden class. This can be useful in situations where additional visual information or cues (such as meaning denoted through the use of color) need to also be conveyed to non-visual users.

<p className="fg-danger">
  <span className="visually-hidden">Danger: </span>
  This action is not reversible
</p>

For visually hidden interactive controls, such as traditional “skip” links, use the .visually-hidden-focusable class. This will ensure that the control becomes visible once focused (for sighted keyboard users). Watch out, compared to the equivalent .sr-only and .sr-only-focusable classes in past versions, CoreUI’s .visually-hidden-focusable is a standalone class, and must not be used in combination with the .visually-hidden class.

<a className="visually-hidden-focusable" href="#content">Skip to main content</a>

Announcing messages

announce() reads a short message to screen reader users without moving focus, for a change the page shows but does not focus, such as a saved form or a filtered list. The toaster store announces every toast through it, whether or not a <CToaster> shows the toast.

import { announce } from '@coreui/react-pro'

announce('3 results')
announce('The connection was lost', { priority: 'high' })

Call it from an event handler or an effect, never while rendering: React may render a component more than once, and every call is a message. In an effect, return what it returns, useEffect(() => announce(message), [message]), so the cleanup cancels the message the first run sent when <StrictMode> runs the effect twice.

Messages go through live regions in every browser: role="log" with aria-live lets assistive technology tell them apart as status messages, as WCAG 2.2 Success Criterion 4.1.3 Status Messages asks. The options follow ariaNotify() from WAI-ARIA 1.3, which announce() does not call yet: Chromium’s source shows Chrome exposing it on ChromeOS and Android without passing it to ChromeVox or TalkBack, and the screen readers on Windows have not been measured with it.

The first call adds a visually hidden live region at the start of <body>. Every call adds a message of its own to it one task later, or 100 ms after a new region was created, so messages sent together each get read, in the order they were sent, and the same text is read again. Messages that are added together, those sent in one task and those that a wait releases at once (the first 100 ms of a region, or one of the waits below), go to the assertive region of their page or dialog when one of them is 'high', the 'high' ones first: with one message in each of the two regions, VoiceOver in Safari read only one of them. While a modal dialog is open the rest of the page is inert and screen readers ignore it, so the message goes to a region inside the dialog instead: the one holding focus, then the one around context, then the last one open in the document. A modal dialog is a native <dialog> opened with showModal(), or a shown element with aria-modal="true", such as the panel of a date picker, whose region leaves with it when the panel is removed. The dialog is picked when the message is added, so one opened right after the call still gets it, and its region leaves with it when it closes. A modal built without a native modal dialog, which hides the rest of the page with aria-hidden or inert, hides these regions as well.

Messages wait while the modal dialog they would go to, or the dialog holding focus, plays its closing transition, and until half a second after Modal, Offcanvas, Dialog or Drawer has closed its dialog. When a modal dialog closes, the rest of the page comes back to screen readers, and VoiceOver dropped a message added at that moment in Chrome, Safari and Firefox. With the wait, VoiceOver in Chrome and Firefox read a toast sent from the modal’s onClose or during the closing transition; after a dialog opened without a button to return to, focus fell to the page and Chrome still skipped it. A <dialog> the page opens and closes itself is not waited for, so send a message meant for the page about half a second after closing it. A message added to a dialog right before it starts closing is lost with it. A toast added together with setVisible(false) after an await can reach the dialog before its transition starts, so add it from onClose instead. Safari also skipped a message sent while the page was still loading, and read one sent a second later.

Option	Type	Default	Description
`context`	element	`null`	The element the message comes from. When focus is in no modal dialog, the dialog around it gets the message, which is how a dialog inside a shadow root, where the page cannot look, is found.
`priority`	`'normal'` \| `'high'`	`'normal'`	`'normal'` adds the message to the polite region, which waits until the screen reader is idle, unless it is added together with a `'high'` one; `'high'` adds it to the assertive region, which interrupts; keep it for the few messages that cannot wait. Some screen readers read both as polite.
`timeout`	number	`7000`	Time (ms) the message stays in the region once added; `0` keeps it until it is removed.

announce() returns a function that removes the message, or cancels it before it is added, for a status that a newer one replaces. It is the function @coreui/coreui-pro exports, so React components and vanilla plugins on one page add to the same regions, each copy with its own queue, and a dialog holds only the queue of the copy it comes with.

Reduced motion

CoreUI for React includes support for the prefers-reduced-motion media feature. In browsers/environments that allow the user to specify their preference for reduced motion, most CSS transition effects in CoreUI for React (for instance, when a modal dialog is opened or closed, or the sliding animation in carousels) will be disabled, and meaningful animations (such as spinners) will be slowed down.

On browsers that support prefers-reduced-motion, and where the user has not explicitly signaled that they’d prefer reduced motion (i.e. where prefers-reduced-motion: no-preference), CoreUI for React enables smooth scrolling using the scroll-behavior property.