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-equivattribute value of"refresh"; and - the element has a valid
contentattribute 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
- 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
2.2.4 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
failedoutcomes: success criterion is not satisfied - All
passedoutcomes: success criterion needs further testing - An
inapplicableoutcome: success criterion needs further testing
- Any
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
failedoutcomes: success criterion is not satisfied - All
passedoutcomes: success criterion needs further testing - An
inapplicableoutcome: success criterion needs further testing
- Any
G110: Using an instant client-side redirect
- Learn more about technique G110
- Not required for conformance to any W3C accessibility recommendation.
- Outcome mapping:
- Any
failedoutcomes: technique is not satisfied - All
passedoutcomes: technique needs further testing - An
inapplicableoutcome: technique needs further testing
- Any
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
failedoutcomes: technique is not satisfied - All
passedoutcomes: technique needs further testing - An
inapplicableoutcome: technique needs further testing
- Any
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.
Test Cases
Passed
Passed Example 1
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
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
This meta element refreshes the page after 30 seconds.
<head>
<meta http-equiv="refresh" content="30" />
</head>
Failed Example 2
This meta element redirects the user after 20 hours.
<head>
<meta http-equiv="refresh" content="72001; URL='https://w3.org'" />
</head>
Failed Example 3
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
This meta element has no content attribute.
<head>
<meta http-equiv="refresh" />
</head>
Inapplicable Example 2
This meta element has no http-equiv="refresh" attribute.
<head>
<meta content="72001" />
</head>
Inapplicable Example 3
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
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
This meta element has an invalid content attribute, and is therefore inapplicable.
<head>
<meta http-equiv="refresh" content="; 72001" />
</head>
Inapplicable Example 6
This meta element has an invalid content attribute, and is therefore inapplicable.
<head>
<meta http-equiv="refresh" content="" />
</head>
Inapplicable Example 7
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
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:
- 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 eitherImage Button(the state) orimage(the keyword mapping to it), both formulations having the same meaning; similarly, “an input element with atypeattribute value ofText” can be either<input type="text" />,<input />(missing value default), or<input type="invalid" />(invalid value default). - For boolean attributes, the attribute value is
truewhen the attribute is present andfalseotherwise. Thus<button disabled>,<button disabled="disabled">and<button disabled="">all have adisabledattribute value oftrue. - 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
This is the first version of this ACT rule.
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 (semi-automated) 0.57.2 | Semi-automated tool | Consistent | |
| Axe DevTools Pro 4.37.1 | Semi-automated tool | Consistent | |
| Axe-core 4.8.1 | Automated tool | Consistent | |
| Equal Access Accessibility Checker 3.1.42-rc.0 | Automated tool | Partial | |
| QualWeb 3.0.0 | Automated tool | Partial | |
| Total Validator 17.1.0 | Linter | Consistent | |
| Total Validator (+Browser) 17.3.0 | Automated tool | Consistent | |