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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:

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

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

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:

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

Open in a new tab

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

Open in a new tab

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

Open in a new tab

This meta element refreshes the page after 30 seconds.

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

Failed Example 2

Open in a new tab

This meta element redirects the user after 20 hours.

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

Failed Example 3

Open in a new tab

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

Open in a new tab

This meta element has no content attribute.

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

Inapplicable Example 2

Open in a new tab

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

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

Inapplicable Example 3

Open in a new tab

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>

Inapplicable Example 4

Open in a new tab

This meta element has an invalid content attribute, and is therefore inapplicable.

<head>
	<meta http-equiv="refresh" content="-00.12 foo" />
</head>

Inapplicable Example 5

Open in a new tab

This meta element has an invalid content attribute, and is therefore inapplicable.

<head>
	<meta http-equiv="refresh" content="; 72001" />
</head>

Inapplicable Example 6

Open in a new tab

This meta element has an invalid content attribute, and is therefore inapplicable.

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

Inapplicable Example 7

Open in a new tab

This meta element has an invalid content attribute, and is therefore inapplicable.

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

Inapplicable Example 8

Open in a new tab

This meta element has an invalid content attribute, and is therefore inapplicable.

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

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:

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:

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, 20 December 2023

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) 0.57.2 Automated tool Consistent Alfa (fully automated) Report
Alfa (semi-automated) 0.57.2 Semi-automated tool Consistent Alfa (semi-automated) Report
Axe DevTools Pro 4.37.1 Semi-automated tool Consistent Axe DevTools Pro Report
Axe-core 4.8.3 Automated tool Consistent Axe-core Report
Equal Access Accessibility Checker 3.1.42-rc.0 Automated tool Partial Equal Access Accessibility Checker Report
Total Validator 17.4.0 Linter Consistent Total Validator Report
Total Validator (+Browser) 17.4.0 Automated tool Consistent Total Validator (+Browser) Report
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