Meta element has no refresh delay

Description

This rule checks that the meta element is not used for delayed redirecting or refreshing.

Applicability

This rule applies to the first meta element in a document for which all the following are true:

• the element has an http-equiv attribute value of "refresh"; and
• the element has a valid content attribute value, as described in the meta refresh pragma directive.

Expectation

For each target, the time from the content attribute value is between 0 and 72000 (20 hours). To determine the time, run the shared declarative refresh steps on the meta element as described in the HTML refresh state.

Assumptions

• This rule assumes no functionality was provided by the website for the user to adjust the timer.
• This rule assumes that the refresh was not essential, which is listed as a valid exception to 2.2.1 Time Adjustable.

Accessibility Support

Not all major web browsers parse the value of the content attribute in the same way. Some major browsers, when they are unable to parse the value, default to a 0 seconds delay, whereas others will not redirect at all. This can cause some pages to be inapplicable for this rule, while still having a redirect in a minority of web browsers.

Background

Because a refresh with a timing of 0 is a redirect, it is exempt from this rule. Since this can cause rapid screen flashes it is strongly recommended to avoid this.

This rule is designed specifically for 2.2.1 Timing Adjustable, which can be satisfied if the time limit is over 20 hours long. All pages that fail this because of a “refresh” meta element also do not satisfy 3.2.5 Change on Request. In order to adequately test the expectation, some of the passed examples do not satisfy 3.2.5 Change on Request.

Bibliography

• Understanding Success Criterion 2.2.1: Timing Adjustable
• Understanding Success Criterion 2.2.4: Interruptions
• Understanding Success Criterion 3.2.5: Change on Request
• G110: Using an instant client-side redirect
• H76: Using meta refresh to create an instant client-side redirect
• F40: Failure of Success Criterion 2.2.1 and 2.2.4 due to using meta redirect with a time limit
• F41: Failure of Success Criterion 2.2.1, 2.2.4, and 3.2.5 due to using meta refresh with a time-out

Accessibility Requirements Mapping

• 2.2.1 Timing Adjustable (Level A)

  • Learn more about 2.2.1 Timing Adjustable
  • 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
• 2.2.4 Interruptions (Level AAA)

  • Learn more about 2.2.4 Interruptions
  • Required for conformance to WCAG 2.0 and later on level AAA.
  • 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
• 3.2.5 Change on Request (Level AAA)

  • Learn more about 3.2.5 Change on Request
  • Required for conformance to WCAG 2.0 and later on level AAA.
  • 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
• G110: Using an instant client-side redirect

  • Learn more about technique G110
  • Not required for 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
• H76: Using meta refresh to create an instant client-side redirect

  • Learn more about technique H76
  • Not required for 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

Input Aspects

The following aspects are required in using this rule.

• DOM Tree

Test Cases

Passed

Passed Example 1

Open in a new tab

This page redirects to a new page immediately.

<head>
	<meta http-equiv="refresh" content="0; URL='https://github.com'" />
</head>

Passed Example 2

Open in a new tab

The first valid meta element on this page redirects to a new page immediately.

<head>
	<meta http-equiv="refresh" content="0; https://w3.org" />
	<meta http-equiv="refresh" content="5; https://w3.org" />
</head>

Passed Example 3

Open in a new tab

This page redirects after more than 20 hours.

<head>
	<meta http-equiv="refresh" content="72001; https://w3.org" />
</head>

Failed

Failed Example 1

Open in a new tab

This page refreshes after 30 seconds.

<head>
	<meta http-equiv="refresh" content="30" />
</head>
<body>
	<p>This page refreshes after 30 seconds.</p>
</body>

Failed Example 2

Open in a new tab

This page redirects to a new page after 30 seconds.

<head>
	<meta http-equiv="refresh" content="30; URL='https://w3.org'" />
</head>
<body>
	<p>This page redirects afte 30 seconds.</p>
</body>

Failed Example 3

Open in a new tab

The first meta element on this page is not valid because it uses colon (“:”) rather than semicolon (“;”). The second meta element redirects to a new page after 5 seconds.

<head>
	<meta http-equiv="refresh" content="0: https://w3.org" />
	<meta http-equiv="refresh" content="5; https://w3.org" />
</head>
<body>
	<p>This page refreshes after 5 seconds.</p>
</body>

Failed Example 4

Open in a new tab

This page redirects to a new page after exactly 20 hours.

<head>
	<meta http-equiv="refresh" content="72000; https://w3.org" />
</head>
<body>
	<p>This page redirects after exactly 20 hours.</p>
</body>

Inapplicable

Inapplicable Example 1

Open in a new tab

This page will not refresh because it lacks a content attribute.

<head>
	<meta http-equiv="refresh" />
</head>
<body>
	<p>This page does not refresh.</p>
</body>

Inapplicable Example 2

Open in a new tab

This page will not refresh because it lacks a http-equiv attribute.

<head>
	<meta content="30" />
</head>
<body>
	<p>This page does not refresh.</p>
</body>

Inapplicable Example 3

Open in a new tab

This ‘meta’ element contains an invalid content attribute and will not refresh the page.

<head>
	<meta http-equiv="refresh" content="0: https://w3.org" />
</head>
<body>
	<p>This page does not redirect.</p>
</body>

Inapplicable Example 4

Open in a new tab

This ‘meta’ element contains an invalid content attribute and will not refresh the page.

<head>
	<meta http-equiv="refresh" content="-00.12 foo" />
</head>
<body>
	<p>This page does not refresh.</p>
</body>

Inapplicable Example 5

Open in a new tab

This ‘meta’ element contains an invalid content attribute and will not refresh the page.

<head>
	<meta http-equiv="refresh" content="; 30" />
</head>
<body>
	<p>This page does not refresh.</p>
</body>

Inapplicable Example 6

Open in a new tab

This ‘meta’ element contains an invalid content attribute and will not refresh the page.

<head>
	<meta http-equiv="refresh" content="" />
</head>
<body>
	<p>This page does not refresh.</p>
</body>

Inapplicable Example 7

Open in a new tab

This ‘meta’ element contains an invalid content attribute and will not refresh the page.

<head>
	<meta http-equiv="refresh" content="+5; https://w3.org" />
</head>
<body>
	<p>This page does not redirect.</p>
</body>

Inapplicable Example 8

Open in a new tab

This ‘meta’ element contains an invalid content attribute and will not refresh the page.

<head>
	<meta http-equiv="refresh" content="foo; URL='https://w3.org'" />
</head>
<body>
	<p>This page does not redirect.</p>
</body>

Glossary

Attribute value

The attribute value of a content attribute set on an HTML element is the value that the attribute gets after being parsed and computed according to specifications. It may differ from the value that is actually written in the HTML code due to trimming whitespace or non-digits characters, default values, or case-insensitivity.

Some notable case of attribute value, among others:

• For enumerated attributes, the attribute value is either the state of the attribute, or the keyword that maps to it; even for the default states. Thus <input type="image" /> has an attribute value of either Image Button (the state) or image (the keyword mapping to it), both formulations having the same meaning; similarly, “an input element with a type attribute value of Text” can be either <input type="text" />, <input /> (missing value default), or <input type="invalid" /> (invalid value default).
• For boolean attributes, the attribute value is true when the attribute is present and false otherwise. Thus <button disabled>, <button disabled="disabled"> and <button disabled=""> all have a disabled attribute value of true.
• For attributes whose value is used in a case-insensitive context, the attribute value is the lowercase version of the value written in the HTML code.
• For attributes that accept numbers, the attribute value is the result of parsing the value written in the HTML code according to the rules for parsing this kind of number.
• For attributes that accept sets of tokens, whether space separated or comma separated, the attribute value is the set of tokens obtained after parsing the set and, depending on the case, converting its items to lowercase (if the set is used in a case-insensitive context).
• For aria-* attributes, the attribute value is computed as indicated in the WAI-ARIA specification and the HTML Accessibility API Mappings.

This list is not exhaustive, and only serves as an illustration for some of the most common cases.

The attribute value of an IDL attribute is the value returned on getting it. Note that when an IDL attribute reflects a content attribute, they have the same attribute value.

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.

Rule Versions

1. Latest version, 25 October 2022

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.

Implementation	Type	Consistency	Report
Alfa (fully automated) 0.80.0	Automated tool	Consistent
Alfa (semi-automated) 0.80.0	Semi-automated tool	Consistent
Axe DevTools Pro 4.37.1	Semi-automated tool	Consistent
Axe-core 4.8.3	Automated tool	Consistent
Equal Access Accessibility Checker 3.1.42-rc.0	Automated tool	Consistent
QualWeb 3.0.0	Automated tool	Partial
SortSite 6.45	Automated tool	Consistent
Total Validator 17.4.0	Linter	Consistent
Total Validator (+Browser) 17.4.0	Automated tool	Consistent