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.
Background
The meta http-equiv="refresh"
directive is an HTML tag used to instruct browsers to automatically refresh or reload a web page after a specified time interval. This can be useful for updating content dynamically or redirecting users to another page.
The content
attribute in the meta http-equiv="refresh"
directive is used to define the time interval, in seconds, after which the browser should automatically refresh or reload the web page. For example, content="5"
would instruct the browser to refresh the page every 5 seconds. Careful consideration of the refresh interval is crucial to ensure optimal user experience and accessibility, particularly for individuals who may require more time to consume or interact with web content.
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.
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.
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
failed
outcomes: success criterion is not satisfied - All
passed
outcomes: success criterion needs further testing - An
inapplicable
outcome: 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
failed
outcomes: success criterion is not satisfied - All
passed
outcomes: success criterion needs further testing - An
inapplicable
outcome: 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
failed
outcomes: technique is not satisfied - All
passed
outcomes: technique needs further testing - An
inapplicable
outcome: 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
failed
outcomes: technique is not satisfied - All
passed
outcomes: technique needs further testing - An
inapplicable
outcome: 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 atype
attribute 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
true
when the attribute is present andfalse
otherwise. Thus<button disabled>
,<button disabled="disabled">
and<button disabled="">
all have adisabled
attribute 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
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 five 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
- cantTell: Whether the rule is applicable, or not all expectations were met could not be fully determined by the tester.
- Untested: The tester has not attempted to evaluate the test subject.
Note: A rule has one passed
or failed
outcome for every test target. When a tester evaluates a test target it can also be reported as cantTell
if the rule cannot be tested in its entirety. For example, when applicability was automated, but the expectations have to be evaluated manually.
When there are no test targets the rule has one inapplicable
outcome. If the tester is unable to determine whether there are test targets there will be one cantTell
outcome. And when no evaluation has occurred the test target has one untested outcome. This means that each test subject always has one or more outcomes.
Outcomes used in ACT Rules can be expressed using the outcome property of the [EARL10-Schema][].
Rule Versions
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.