Focusable element has no keyboard trap

  • Rule Type:composite
  • Rule Id: 80af7b
  • Last modified: Aug 24, 2020
  • Accessibility Requirements Mapping:
    • 2.1.2 No Keyboard Trap (Level A)
      • Learn More about 2.1.2 No Keyboard Trap
      • Required for conformance to WCAG 2.0 and later on level A and higher.
      • Outcome mapping:
        • Any failed outcomes: success criterion is not satisfied.
        • All passed outcomes: success criterion needs further testing.
        • An inapplicable outcome: success criterion needs further testing.
    • WCAG Non-Interference
      • Learn More about WCAG Non-Interference
      • Not required to conformance to any W3C accessibility recommendation.
      • Outcome mapping:
        • Any failed outcomes: WCAG 2 conformance requirement is not satisfied.
        • All passed outcomes: WCAG 2 conformance requirement needs further testing.
        • An inapplicable outcome: WCAG 2 conformance requirement needs further testing.
    • G21: Ensuring that users are not trapped in content
      • Learn More about technique G21
      • Not required to conformance to any W3C accessibility recommendation.
      • Outcome mapping:
        • Any failed outcomes: technique is not satisfied.
        • All passed outcomes: technique needs further testing.
        • An inapplicable outcome: technique needs further testing.

Description

This rule checks for keyboard traps. This includes use of both standard and non-standard keyboard navigation to navigate through all content without becoming trapped.

Applicability

The rule only applies to any HTML or SVG element that is focusable.

Note: This rule only applies to HTML and SVG. Thus, it is a partial check for WCAG 2.0 success criterion 2.1.2, which applies to all content.

Expectation

For each test target, the outcome of one of the following rules is "passed":

Assumptions

There are currently no assumptions.

Accessibility Support

There are no major accessibility support issues known for this rule.

Background

Test Cases

Passed

Passed Example 1

Open in a new tab

No trap for keyboard navigation.

<a href="#">Link 1</a> <button>Button1</button>

Passed Example 2

Open in a new tab

Using tabindex="1".

<div tabindex="1">Text</div>

Passed Example 3

Open in a new tab

Using tabindex="-1".

<div tabindex="-1">Text</div>

Passed Example 4

Open in a new tab

Keyboard trap with help information in a paragraph before, and where the method advised works.

<script>
	var trapOn = false
</script>

<p>Press the M-key to Exit</p>
<a id="link1" href="#">Link 1</a>
<button id="btn1" onblur="(function(e){trapOn=true; document.getElementById('btn2').focus();})(event)">
	Button 1
</button>
<button
	id="btn2"
	onkeydown="(function(e){ if (e.keyCode === 77){trapOn=false;document.getElementById('link2').focus();}})(event)"
	onblur="(function(e){ if(trapOn){document.getElementById('btn1').focus();}})(event)"
>
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Passed Example 5

Open in a new tab

Keyboard trap with help information within the trap, and where the method advised works.

<script>
	var trapOn = false
</script>

<a id="link1" href="#">Link 1</a>
<button id="btn1" onblur="(function(e){trapOn=true; document.getElementById('btn2').focus();})(event)">
	Button 1
</button>
<p>Press the M-key to Exit</p>
<button
	id="btn2"
	onkeydown="(function(e){ if (e.keyCode === 77){trapOn=false;document.getElementById('link2').focus();}})(event)"
	onblur="(function(e){ if(trapOn){document.getElementById('btn1').focus();}})(event)"
>
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Passed Example 6

Open in a new tab

Keyboard trap with "help" link that once clicked exposes the instructions.

<script>
	var trapOn = false

	function showHelpText() {
		document.getElementById('helptext').innerHTML = '<p>Press the M-key to Exit</p>'
	}
</script>

<div onkeydown="(function(e){ if (e.keyCode === 77){trapOn=false;document.getElementById('link2').focus();}})(event)">
	<a id="link1" href="#">Link 1</a>
	<button id="btn1" onblur="(function(e){trapOn=true; document.getElementById('helpLink').focus();})(event)">
		Button 1
	</button>
	<a id="helpLink" href="#" onclick="showHelpText()">How to go the next element</a>
	<div id="helptext"></div>
	<button id="btn2" onblur="(function(e){ if(trapOn){document.getElementById('btn1').focus();}})(event)">
		Button 2
	</button>
</div>
<a id="link2" href="#">Link 2</a>

Failed

Failed Example 1

Open in a new tab

Keyboard trap one element.

<a href="#">Link 1</a>
<button onblur="setTimeout(() => this.focus(), 10)">
	Button1
</button>

Failed Example 2

Open in a new tab

Keyboard trap group.

<button onblur="setTimeout(() => this.nextElementSibling.focus(), 10)">
	Button1
</button>
<button onblur="setTimeout(() => this.previousElementSibling.focus(), 10)">
	Button2
</button>
<button>
	Button3
</button>

Failed Example 3

Open in a new tab

A focusable element between keyboard traps.

<button onblur="setTimeout(() => this.focus(), 10)">Button 1</button>
<button>Button 2</button>
<button onblur="setTimeout(() => this.focus(), 10)">Button 3</button>

Failed Example 4

Open in a new tab

Keyboard trap with no instructions.

<script>
	var trapOn = false
</script>

<a id="link1" href="#">Link 1</a>
<button id="btn1" onblur="(function(e){trapOn=true; document.getElementById('btn2').focus();})(event)">
	Button 1
</button>
<button
	id="btn2"
	onkeydown="(function(e){ if (e.keyCode === 77){trapOn=false;document.getElementById('link2').focus();}})(event)"
	onblur="(function(e){ if(trapOn){document.getElementById('btn1').focus();}})(event)"
>
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Failed Example 5

Open in a new tab

Keyboard trap with instructions that doesn't give advise on the method for proceeding.

<script>
	var trapOn = false
</script>

<p>Go to the next element</p>
<a id="link1" href="#">Link 1</a>
<button id="btn1" onblur="(function(e){trapOn=true; document.getElementById('btn2').focus();})(event)">
	Button 1
</button>
<button
	id="btn2"
	onkeydown="(function(e){ if (e.keyCode === 77){trapOn=false;document.getElementById('link2').focus();}})(event)"
	onblur="(function(e){ if(trapOn){document.getElementById('btn1').focus();}})(event)"
>
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Failed Example 6

Open in a new tab

Keyboard trap with help text, where the method advised doesn't work.

<script>
	var trapOn = false
</script>

<a id="link1" href="#">Link 1</a>
<button id="btn1" onblur="(function(e){trapOn=true; document.getElementById('btn2').focus();})(event)">
	Button 1
</button>
<p>Press the M-key to Exit</p>
<button id="btn2" onblur="(function(e){ if(trapOn){document.getElementById('btn1').focus();}})(event)">
	Button 2
</button>
<a id="link2" href="#">Link 2</a>

Inapplicable

Inapplicable Example 1

Open in a new tab

No focusable element.

<h1>Page 1</h1>

Inapplicable Example 2

Open in a new tab

Disabled element.

<button type="button" disabled>Click Me!</button>

Inapplicable Example 3

Open in a new tab

Hidden element using display:none.

<button type="button" style="display:none;">Click Me!</button>

Inapplicable Example 4

Open in a new tab

Hidden element using visibility:hidden.

<a href="#" style="visibility:hidden;">Link 1</a> <button style="visibility:hidden;">Button1</button>

Glossary

Outcome

An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

  • Inapplicable: No part of the test subject matches the applicability
  • Passed: A test target meets all expectations
  • Failed: A test target does not meet all expectations

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such "interim" results can be expressed with the incomplete outcome.


Useful Links


Implementations

This section is not part of the official rule. It is populated dynamically and not accounted for in the change history or the last modified date. This section will not be included in the rule when it is published on the W3C website.

No Implementations

Implementation reports are not provided for this rule.

Acknowledgments

Table of Contents