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id ebe86a
name Focusable element has no keyboard trap via non-standard navigation
rules_format 1.1
rule_type atomic
description This rule checks if it is possible to use non-standard keyboard navigation to navigate through content where focus is trapped when using standard ways of keyboard navigation.
accessibility_requirements
input_aspects
DOM Tree
CSS Styling
acknowledgments
authors funding
Anne Thyme Nørregaard
Carlos Duarte
Dagfinn Rømen
Geir Sindre Fossøy
Malin Øvrebø
Shadi Abou-Zahra
Stein Erik Skotkjerra
WAI-Tools

Applicability

This rule applies to any HTML or SVG element that is focusable where focus cannot cycle to the browser UI by using standard keyboard navigation.

Expectation 1

For each target element help information is visible and included in the accessibility tree or can be accessed from within the keyboard trap.

Note: As per WCAG 2.0 Success Criterion 2.1.1 Keyboard the help information should be accessible through a keyboard interface.

Expectation 2

The help information explains how to cycle to the browser UI, or on how to get to a point from where it is possible to cycle to the browser UI, using standard keyboard navigation.

Expectation 3

For each target element focus can cycle to the browser UI by using the method advised in the help information.

Note: Cycling back to the browser UI can be done both by moving forward through the tab order and by moving backwards. It is not possible to fulfill this expectation by using browser specific shortcuts to return to the browser UI.

Background

Assumptions

  • It is not possible to use unmodified arrow or tab keys, or other standard exit methods to move focus away.
  • The focus order in keyboard navigation is cyclical, not linear, meaning that the focus order will cycle to the first/last element when it moves away from the last/first element.

Accessibility Support

Some browsers have settings that will immediately cycle focus back to the web document. This fulfills the expectation because focus can cycle to the browser UI and the browser UI cycles focus back to the web document.

Bibliography

Examples

Passed

Passed Example 1

These focusable button elements have scripts that create a keyboard trap. The document includes help information in a paragraph before the button elements and the method advised works to escape the keyboard trap.

<script src="/test-assets/focusable-no-keyboard-trap/keyboard.js"></script>

<p>Press Ctrl+M to Exit</p>
<a id="link1" href="#">Link 1</a>
<button id="btn1" onfocus="trapOn = true" onblur="moveFocusToButton('btn2')" onkeydown="escapeTrapOnCtrlM(event)">
	Button 1
</button>
<button id="btn2" onfocus="trapOn = true" onblur="moveFocusToButton('btn1')" onkeydown="escapeTrapOnCtrlM(event)">
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Passed Example 2

These focusable button elements have scripts that create a keyboard trap. The document includes help information within the trap and the method advised works to escape the keyboard trap.

<script src="/test-assets/focusable-no-keyboard-trap/keyboard.js"></script>

<a id="link1" href="#">Link 1</a>
<button id="btn1" onfocus="trapOn = true" onblur="moveFocusToButton('btn2')" onkeydown="escapeTrapOnCtrlM(event)">
	Button 1
</button>
<p>Press Ctrl+M to Exit</p>
<button id="btn2" onfocus="trapOn = true" onblur="moveFocusToButton('btn1')" onkeydown="escapeTrapOnCtrlM(event)">
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Passed Example 3

These focusable button elements have scripts that create a keyboard trap. The document includes help information in a "help" link that once clicked exposes the instructions to escape the keyboard trap.

<script src="/test-assets/focusable-no-keyboard-trap/keyboard.js"></script>

<div onkeydown="escapeTrapOnCtrlM(event)">
	<a id="link1" href="#">Link 1</a>
	<button id="btn1" onfocus="trapOn = true" onblur="moveFocusTo('helpLink')">
		Button 1
	</button>
	<a id="helpLink" href="#" onclick="showHelpText()">How to go the next element</a>
	<div id="helptext"></div>
	<button id="btn2" onblur="moveFocusTo('btn1')">
		Button 2
	</button>
</div>
<a id="link2" href="#">Link 2</a>

Failed

Failed Example 1

These focusable button elements create a keyboard trap with no instructions.

<script src="/test-assets/focusable-no-keyboard-trap/keyboard.js"></script>

<a id="link1" href="#">Link 1</a>
<button id="btn1" onfocus="trapOn = true" onblur="moveFocusToButton('btn2')" onkeydown="escapeTrapOnCtrlM(event)">
	Button 1
</button>
<button id="btn2" onfocus="trapOn = true" onblur="moveFocusToButton('btn1')" onkeydown="escapeTrapOnCtrlM(event)">
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Failed Example 2

These focusable button elements create a keyboard trap with instructions that don't give advice on the method for proceeding.

<script src="/test-assets/focusable-no-keyboard-trap/keyboard.js"></script>

<p>Go to the next element</p>
<a id="link1" href="#">Link 1</a>
<button id="btn1" onfocus="trapOn = true" onblur="moveFocusToButton('btn2')" onkeydown="escapeTrapOnCtrlM(event)">
	Button 1
</button>
<button id="btn2" onfocus="trapOn = true" onblur="moveFocusToButton('btn1')" onkeydown="escapeTrapOnCtrlM(event)">
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Failed Example 3

These focusable button elements create a keyboard trap with help text, where the method advised doesn't work.

<script src="/test-assets/focusable-no-keyboard-trap/keyboard.js"></script>

<a id="link1" href="#">Link 1</a>
<button id="btn1" onfocus="trapOn = true" onblur="moveFocusToButton('btn2')">
	Button 1
</button>
<p>Press Ctrl+M to Exit</p>
<button id="btn2" onfocus="trapOn = true" onblur="moveFocusToButton('btn1')">
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Inapplicable

Inapplicable Example 1

This focusable button elements do not create a keyboard trap.

<a id="link1" href="#">Link 1</a>
<button id="btn1">Button 1</button>
<button id="btn2">Button 2</button>
<a id="link2" href="#">Link 2</a>