Proposed Meta element has no refresh delay (no exception)

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 0. 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 that no functionality was provided by the website for the user to adjust the timer.

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 effectively a redirect, it is exempt from this rule. Since refreshing the same page with a time of 0 can cause rapid screen flashes it is strongly recommended to avoid this.

Bibliography

Accessibility Requirements Mapping

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

Secondary Requirements

This rule is related to the following accessibility requirements, but was not designed to test this requirements directly. These secondary requirements can either be stricter than the rule requires, or may be satisfied in ways not tested by the rule:

2.2.1 Timing Adjustable (Level A): This success criterion is less strict than this rule. This is because this criterion allows redirects longer than 20 hours. Some of the failed examples satisfy this success criterion.

Input Aspects

The following aspects are required in using this rule.

DOM Tree

Test Cases

Passed

Passed Example 1

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This meta element redirects the user immediately. Users won’t notice the change in context.

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

Passed Example 2

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The first valid meta element redirects immediately.

<head>
	<meta http-equiv="refresh" content="0; https://w3.org" />
	<meta http-equiv="refresh" content="30; https://w3.org" />
</head>

Failed

Failed Example 1

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This meta element refreshes the page after 30 seconds.

<head>
	<meta http-equiv="refresh" content="30" />
</head>

Failed Example 2

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This meta element redirects the user after 20 hours.

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

Failed Example 3

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The first meta element is not valid (because of the colon instead of a semi-colon in the content attribute), the second one redirects after 20 hours.

<head>
	<meta http-equiv="refresh" content="0: https://w3.org" />
	<meta http-equiv="refresh" content="72001; https://w3.org" />
</head>

Inapplicable

Inapplicable Example 1

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This meta element has no content attribute.

<head>
	<meta http-equiv="refresh" />
</head>

Inapplicable Example 2

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This meta element has no http-equiv="refresh" attribute.

<head>
	<meta content="72001" />
</head>

Inapplicable Example 3

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This meta element has an invalid content attribute (because of the colon instead of a semi-colon), and is therefore inapplicable.

<head>
	<meta http-equiv="refresh" content="0: http://example.com" />
</head>