From MWBP to WCAG 2.0: Making content that meets Mobile Web Best Practices also meet Web Content Accessibility Guidelines 2.0
W3C Working Group Note 9 July 2009
Introduction
This page is part of a multi-page document. Please refer to the “How to Use This Document” section for more information.
For those familiar with Mobile Web Best Practices (MWBP), this page describes what also needs to be done to meet Web Content Accessibility Guidelines 2.0.
Summary of work required to make content that meets MWBP also meet WCAG 2.0
Compliance with the MWBP helps go some way towards achieving compliance with some WCAG 2.0 success criteria. This section provides a summary of these success criteria. There are three possible levels of effort required, labelled for simplicity with the keywords nothing, something and everything. To summarise, if your content already complies with the MWBP, to achieve compliance with WCAG 2.0, you need to do the following:
Nothing: If a provision is labelled “Nothing” then content that complies with MWBP already complies with the provision and no further effort is necessary.The following list includes all of the provisions that are marked “Nothing”. Links in this section point to the relevant provisions.
Something: If a provision is labelled “Something” then more effort of some kind is necessary to comply with the provision. All of the provisions marked “Something” are included in the list below. Each item in the list is a link to an explanation of what is required, in the next section of this report. For each there is a list of the provisions that may provide some compliance or are in some way related. There is no direct correspondence between one provision and another. In some cases, it may be necessary to make an extra effort or to consider a more diverse range of user needs. In these cases, the word “possibly” is used. In other cases scope may be different, giving partial compliance. In these cases the word “partially” is used. SC links in this section point to the detail section below; BP links in this section point to the MWBP Recommendation.
- 1.3.1 Info and Relationships partially covered in different ways by each of FONTS, STRUCTURE, STYLE_SHEETS_SUPPORT, STYLE_SHEETS_USE.
- 1.3.2 Meaningful Sequence possibly covered by TABLES_LAYOUT.
- 1.4.3 Contrast (Minimum), possibly covered in different ways by each of BACKGROUND_IMAGE_READABILITY and COLOR_CONTRAST.
- 1.4.6 Contrast (Enhanced), possibly covered in different ways by each of BACKGROUND_IMAGE_READABILITY and COLOR_CONTRAST.
- 1.4.8 Visual Presentation, partially covered by SCROLLING.
- 2.1.1 Keyboard possibly covered by OBJECTS_OR_SCRIPT.
- 2.1.3 Keyboard (No Exception) possibly covered by OBJECTS_OR_SCRIPT
- 2.4.2 Page Titled, possibly covered by PAGE_TITLE.
- 2.4.4 Link Purpose (In Context), covered by LINK_TARGET_ID, possibly partially covered by IMAGE_MAPS.
- 2.4.6 Headings and Labels, possibly partially covered in different ways by each of STRUCTURE and CONTROL_LABELLING.
- 2.4.9 Link Purpose (Link Only), covered by LINK_TARGET_ID.
- 3.1.5 Reading Level, possibly covered by CLARITY.
- 3.2.1 On Focus, partially covered by POP_UPS.
- 3.2.2 On Input, partially covered by POP_UPS.
- 3.2.3 Consistent Navigation partially covered by NAVIGATION.
- 3.2.5 Change on Request, possibly covered in different ways by each of AUTO_REFRESH, POP_UPS and REDIRECTION.
- 3.3.2 Labels or Instructions, partially covered in different ways by each of CONTROL_LABELLING and CONTROL_POSITION.
- 4.1.2 Name, Role, Value, partially covered in different ways by each of CONTROL_LABELLING and NO_FRAMES.
Everything: For all other success criteria, the MWBP do not ensure compliance and it will be necessary to do the work involved. These SCs are not related to any MWBPs.
- 1.2.1 Audio-only and Video-only (Prerecorded)
- 1.2.2 Captions (Prerecorded)
- 1.2.3 Audio Description or Media Alternative (Prerecorded)
- 1.2.4 Captions (Live)
- 1.2.5 Audio Description
- 1.2.6 Sign Language
- 1.2.7 Audio Description (Extended)
- 1.2.8 Full Text Alternative
- 1.2.9 Live Audio-only
- 1.3.3 Sensory Characteristics
- 1.4.2 Audio Control
- 1.4.5 Images of Text
- 1.4.7 Low or No Background Audio
- 1.4.9 Images of Text (No Exception)
- 2.1.2 No Keyboard Trap
- 2.2.1 Timing Adjustable
- 2.2.2 Pause, Stop, Hide
- 2.2.3 No Timing
- 2.2.4 Interruptions
- 2.2.5 Re-authenticating
- 2.3.1 Three Flashes or Below Threshold
- 2.3.2 Three Flashes
- 2.4.1 Bypass Blocks
- 2.4.5 Multiple Ways
- 2.4.7 Focus Visible
- 2.4.8 Location
- 3.1.1 Language of Page
- 3.1.2 Language of Parts
- 3.1.3 Unusual Words
- 3.1.4 Abbreviations
- 3.1.6 Pronunciation
- 3.2.4 Consistent Identification
- 3.3.1 Error Identification
- 3.3.3 Error Suggestion
- 3.3.4 Error Prevention (Legal, Financial, Data)
- 3.3.5 Help
- 3.3.6 Error Prevention (All)
Addressing WCAG 2.0 Success Criteria
This section lists each of the WCAG success criteria that are related to MWBP, which are listed under “something” above. For each SC, the section title is that of the SC. This is followed by a quotation of the text of the SC (sometimes abbreviated) and a list of the BPs that can help meet it.
1.3.1 Info and Relationships
Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text. (Level A)
- FONTS partially covers some of the sufficient techniques.
- STRUCTURE helps towards compliance with this success criterion. Although the BP title covers structural elements in general, it doesn't enumerate them. Using other commonly-accepted structural elements not mentioned in the BP can improve usability for mobile users as well as accessibility, and go some way toward compliance with this success criterion. These elements include lists, quotations and citations, table markup, and semantic aspects such as emphasis.
- STYLE_SHEETS_SUPPORT partially helps: In order to create content that can be read without style sheets it will probably be necessary to use structural markup, and so this helps compliance.
- STYLE_SHEETS_USE possibly helps: If content is styled with style sheets it will probably use structural markup, and so this may indirectly bring the same accessibility benefits as STYLE_SHEETS_SUPPORT, above.
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1.3.2 Meaningful Sequence
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1.4.3 Contrast (Minimum)
The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for following: (Level AA)
- Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;
- Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.
- Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.
- BACKGROUND_IMAGE_READABILITY helps with meeting this SC.
- COLOR_CONTRAST possibly helps with meeting this SC. However, the BP is concerned with unfavorable ambient light and the ability of devices to display contrasting color at all, while users may have color blindness and color perception deficits, which may lead to different results. Using the more precise criteria given in WCAG 2.0 may help ensure compliance. Note that WCAG 2.0 suggests a Contrast Ratio and the size of text to which the ratio applies.
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1.4.6 Contrast (Enhanced)
The visual presentation of text and images of text has a contrast ratio of at least 7:1, except for...: (Level AAA)
- BACKGROUND_IMAGE_READABILITY helps with meeting this SC.
- COLOR_CONTRAST possibly helps with meeting this SC. However, the BP is concerned with unfavorable ambient light and the ability of devices to display contrasting color at all, while users may have color blindness and color perception deficits, which may lead to different results. Using the more precise criteria given in WCAG 2.0 it may help ensure compliance. Note that WCAG 2.0 suggests a Contrast Ratio and the size of text to which the ratio applies.
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1.4.8 Visual Presentation
For the visual presentation of blocks of text, a mechanism is available to achieve the following: (Level AAA)
- foreground and background colors can be selected by the user.
- width is no more than 80 characters or glyphs (40 if CJK).
- text is not justified (aligned to both the left and the right margins).
- line spacing (leading) is at least space-and-a-half within paragraphs, and paragraph spacing is at least 1.5 times larger than the line spacing.
- text can be resized without assistive technology up to 200 percent in a way that does not require the user to scroll horizontally to read a line of text on a full-screen window.
- SCROLLING partially helps ensure compliance with the last aspect of this SC (number 5 in the list).
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All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes, except where the underlying function requires input that depends on the path of the user's movement and not just the endpoints. (Level A)
- OBJECTS_OR_SCRIPT may possibly help: As non-compliance derives from the use of scripting or objects, content that does not use these, or in which they are used in a redundant way, complies with this this SC.
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2.1.3 Keyboard (No Exception)
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2.4.2 Page Titled
Web pages have titles that describe topic or purpose
- PAGE_TITLE may possibly help. However, the accessibility techniques are more detailed, and in particular may lead to a title that is longer than suitable for a mobile device. Tip: While for the mobile context it is important to keep the title short, for the general user it is also important to provide an adequate description. One way to do this (known as “front loading”) is to place the most differentiating information first. More generic information (for example the section of a site) can be placed following this, or omitted for mobile delivery.
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2.4.4 Link Purpose (In Context)
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2.4.6 Headings and Labels
Headings and labels describe topic or purpose. (Level AA)
- STRUCTURE may help comply with this SC as regards the use of headings.
- CONTROL_LABELLING may help comply with this SC as regards the use of form labels.
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2.4.9 Link Purpose (Link Only)
A mechanism is available to allow the purpose of each link to be identified from link text alone, except where the purpose of the link would be ambiguous to users in general. (Level AAA)
- LINK_TARGET_ID may ensure compliance with this success criterion. However, the intent of the SC is to ensure that users can identify the purpose of the link out of context (for example, in a list of links created by the user agent). The SC also requires consistent identification (same destination, same description).
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3.1.5 Reading Level
When text requires reading ability more advanced than the lower secondary education level after removal of proper names and titles, supplemental content, or a version that does not require reading ability more advanced than the lower secondary education level, is available. (Level AAA)
- CLARITY may possibly help but it concerns a different aspect of language comprehension. WCAG is concerned with a user's reading ability, while this BP is concerned with reading difficulty due to context of use (for example, small screen, distracting environnment, lack of time).
When any component receives focus, it does not initiate a change of context. (Level A)
- POP_UPS partially covers this SC (as it concerns popup windows). WCAG 2.0 considers a number of different changes of context and a popup window is just one of them.
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Changing the setting of any user interface component does not automatically cause a change of context unless the user has been advised of the behavior before using the component. (Level A)
- POP_UPS partially covers this SC (as it concerns popup windows). WCAG 2.0 considers a number of different changes of context and a popup window is just one of them.
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3.2.3 Consistent Navigation
Navigational mechanisms that are repeated on multiple Web pages within a set of Web pages occur in the same relative order each time they are repeated, unless a change is initiated by the user. (Level AA)
- NAVIGATION helps partially, although WCAG is more detailed and specific (“same relative order”) than the MWBP (“same navigation”).
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3.2.5 Change on Request
Changes of context are initiated only by user request or a mechanism is available to turn off such changes. (Level AAA)
- AUTO_REFRESH may possibly help. This SC requires that refresh be started only by user request, but this BP concerns using auto-refresh started automatically and stopped by user request. If auto-refresh is used compliance is not necessarily achieved. However, if auto-refresh is not used at all, this does ensure compliance with the success criterion.
- POP_UPS partially covers this SC (as it concerns popup windows). WCAG 2.0 considers a number of different changes of context and a popup window is just one of them.
- REDIRECTION may partially help. It ensures that redirection is initiated only by user request, and therefore ensures compliance in the automatic redirects situation.
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3.3.2 Labels or Instructions
Labels or instructions are provided when content requires user input. (Level A)
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4.1.2 Name, Role, Value
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Updated 27 June 2009.