Are browser dialog boxes accessible?

Question

Are browser dialog boxes considered accessible by WCAG A/AA standards? The dialog boxes I am referring to are the ones that are native to the browser like the following in Chrome:

Answer 1

Browser dialog box are accessible as long as your browser follows the UAAG requirements, which should be the case for the most modern used browsers (Edge, Safari, Chrome, Firefox, ...).

In your example, this dialogbox is launched when the window.onbeforeunload event is fired.

It can be a good solution to answer to the WCAG 3.2.5 point:

3.2.5 Change on Request: Changes of context are initiated only by user request or a mechanism is available to turn off such changes. (Level AAA)

http://www.w3.org/TR/UNDERSTANDING-WCAG20/consistent-behavior-no-extreme-changes-context.html

So this prevent, for instance, a third party script to redirect the user outside of the page without its confirmation, or the user to mistakenly close the wrong window.

But of course, opening a dialog box when not the result of a user action is not accessible.

Answer 2

There are 3 different Guidelines from W3C/WAI (Web Accessibility Initiative):

• WCAG 2.0 for Web Content
• ATAG for Authoring Tool (tl;dr CMS)
• UAAG for User Agents (tl;dr graphical web browsers and many more like sites that'll embed content - ads, videos, weather forecast, etc)

The relevant guideline for browser dialog boxes is UAAG as in "does the UA expose web content in an accessible manner and are its own controls accessible - mouse and touch and keyboard, playing well with OS accessibility APIs"

Following ATAG allows a disabled person to create content on its own website as an admin or content writer or translator and such. A website can be accessible to its visitors but the backoffice/admin also needs to be accessible to employees, content producers, etc

And finally, there's also WAI-ARIA for Accessible Rich Internet Applications for rich widgets, web applicaitons whatever it means. tl;dr should be used as a complement to HTML5