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SearchShared Web Experiences: Barriers Common to Mobile Device Users and People
with Disabilities
[Editors' Draft, 25 May 2009]
Status: This document is an in-progress Editor's
Draft. The published version is at www.w3.org/WAI/mobile/experiences.
Please send comments to wai-eo-editors@w3.org (a publicly archived list).
People with disabilities using computers have similar interaction limitations as people without disabilities who are using mobile devices. Both experience similar barriers when interacting with Web sites. There is also significant overlap between the design solutions for both. For more information, see:
- Web Content Accessibility and Mobile Web: Making a Web Site Accessible Both for People with Disabilities and for Mobile Devices introduces the overlap between W3C guidelines for accessibility and best practices for mobile devices and links to detailed technical resources.
- Introduction to Web Accessibility
- How People with Disabilities Use the Web
This page provides examples of barriers that people with disabilities and people using mobile devices experience when interacting with Web content. For a comprehensive comparison, see Relationship between Mobile Web Best Practices (MWBP) and Web Content Accessibility Guidelines (WCAG). Mobile devices vary widely and not all the problems are present on all models. These barriers are grouped under four principles: perceivable, operable, understandable and robust. These principles lay the foundation necessary for anyone to access and use Web content, as described in Understanding the Four Principles of Accessibility section of Introduction to Understanding WCAG 2.0.
Shared experiences discussed below are also available in tabular format.
This page includes links to some relevant solutions in:
- Web Content Accessibility Guidelines (WCAG) 1.0
- Web Content Accessibility Guidelines (WCAG) 2.0
- Mobile Web Best Practices 1.0
Contents
- Perceivable
- Information conveyed solely with color
- Large pages or large images
- Multimedia with no captions
- Audio-only prompts (beeps) for important information (warnings, errors)
- Non-text objects (images, sound, video) with no text alternative
- Text entry
- Content formatted using tables or CSS, and reading order not correct when linearized (for example when CSS or tables not rendered)
- Information conveyed only using CSS (visual formatting)
- Operable
- Understandable
- Robust
Perceivable
Information and user interface components must be presentable to users in ways they can perceive.
Experiences discussed below are also available in tabular format.
Information conveyed solely with color
User perceives color incorrectly or not at all, and so misses or misunderstands information or makes mistakes.
Disabilities Context: User who is blind or colorblind perceives color incorrectly or not at all.
- WCAG 2.0 success criteria: 1.4.1 Use of Color,
- 1.3.1 Info and Relationships,
- 1.4.3 Contrast (Minimum) and
- 1.4.6 Contrast (Enhanced).
Mobile Context: Many screens have limited color palette and color difference is not presented. Device is used in poor lighting (for example, outdoors), so colors are not clearly perceived.
- MWBP 1.0 Best Practice: USE_OF_COLOR and
- COLOR_CONTRAST.
Large pages or large images
User only sees small areas at a time, is unable to relate different areas of a page, and so becomes disoriented or has to scroll excessively. Additionally, user cannot access picture details because the picture is shrunk.
Disabilities Context: User with restricted field of vision or using screen magnifier gets only small part of page or image at a time.
- WCAG 1.0 Checkpoint: 12.3.
- WCAG 2.0 Success Criteria: 1.4.8 Visual Presentation.
Mobile Context: Mobile device has small screen (viewport).
- MWBP 1.0 Best Practice: PAGE_SIZE_USABLE and SCROLLING.
Multimedia with no captions
User misses auditory information.
Disabilities Context: User who is deaf or hard of hearing cannot hear.
- WCAG 2.0 Success Criteria: 1.2.2 Captions (Prerecorded), 1.2.4 Captions (Live) and 1.2.8 Media Alternative (Prerecorded).
Mobile Context: Mobile users often turn off sound in public places (trains, hotel lobbies); or often cannot hear in noisy places (streets, nightclubs).
- MWBP 1.0 Best Practice: NON-TEXT-ALTERNATIVES.
Audio-only prompts (beeps) for important information (warnings, errors)
User cannot operate or interact correctly with content, misses prompts, makes mistakes.
Disabilities Context: User who is deaf or hard of hearing cannot perceive content.
- WCAG 2.0 Success Criteria: 1.2.1 Audio-only and Video-only (Prerecorded)
Mobile Context: Users often cannot hear in noisy (street, nightclub) or in public places (trains, hotel lobbies).
- MWBP 1.0 Best Practice: NON_TEXT_ALTERNATIVES.
Non-text objects (images, sound, video) with no text alternative
User cannot perceive important information or loses information due to lack of alternative.
Disabilities Context: User who is blind cannot perceive content that include non-text objects. Furthermore, information not available to user whose browser, assistive technology, other user agent doesn't support object.
- WCAG 1.0 Checkpoint: 1.1.
- WCAG 2.0 Success Criteria: 1.1.1 Non-text content.
Mobile Context: User can be billed for download volume so images might be turned off to save costs. Some mobile user agents have limited support to non-text objects so user losses information. Some user agents also shrunk images in size to fit the device's screen which can make images meaningless.
- MWBP 1.0 Best Practice: NON_TEXT_ALTERNATIVES and OBJECTS_OR_SCRIPT.
Text entry
User has difficulty entering text so text is entered incorrectly or mistakes are made.
Disabilities Context: User with motor disability (for example, partial paralysis, hand tremor, lack of sensitivity, coordination) has difficulty entering information.
- WCAG 2.0 Guideline: 3.3 Input Assistance: Help users avoid and correct mistakes.
Mobile Context: Device has small keypad which has limited functionality compared to a full keyboard, or is held in an unsteady hand.
- MWBP 1.0 Best Practice: MINIMIZE_KEYSTROKES,
- PROVIDE_DEFAULTS and
- DEFAULT_INPUT_MODE.
Content formatted using tables or CSS, and reading order not correct when linearized (for example when CSS or tables not rendered)
User cannot understand the content correctly when it's presented in a linear order.
Disabilities Context: User who is blind reads content in document tree order.
- WCAG 2.0 Success Criteria: 1.3.2 Meaningful Sequence.
Mobile Context: Meaning of content can be changed because of reformatting or restructuring in adaptation process.
- MWBP 1.0 Best Practice: TABLES_LAYOUT, TABLES_NESTED and TABLES_ALTERNATIVES.
Information conveyed only using CSS (visual formatting)
User is unable to access information encoded in visual formatting or in CSS.
Disabilities Context: User who is blind doesn't perceive visual formatting effects.
- WCAG 1.0 Checkpoint: 6.1.
- WCAG 2.0 Success Criteria: 1.3.1 Info and relationship.
Mobile Context: Often no or limited CSS support or diverging CSS support by mobile browser.
- MWBP 1.0 Best Practice: STYLE_SHEETS_SUPPORT.
Operable
User interface components and navigation must be operable.
Experiences discussed below are also available in tabular format.
Mouse required for interaction and navigation
User is unable to navigate all content, or wastes time moving through numerous links.
Disabilities Context: Some users with a motor disability cannot use a mouse. Users who are blind also do not use the mouse.
- WCAG 2.0 Guideline: 2.1 Keyboard Accessible.
Mobile Context: Device has no mouse, only alphanumeric keypad or joystick.
- MWBP 1.0 Best Practice: OBJECTS_OR_SCRIPT, IMAGE_MAPS, NAVBAR, BALANCE and ACCESS_KEYS.
Scripting required to operate content
User cannot operate the content so loses some information.
Disabilities Context: User's assistive technology or browser doesn't support scripting.
- WCAG 2.0 Conformance Requirement: Conformance Requirement 4: Only Accessibility-Supported Ways of Using Technologies and
- Conformance Requirement 5: Non-Interference.
Mobile Context: Scripting turned off or not supported.
- MWBP 1.0 Best Practice: OBJECTS_OR_SCRIPT.
Special plugin required
User can not perceive content or can not operate interface.
Disabilities Context: Plugin turned off, or not installed, or not compatible with assistive technology. Plugin not operable with preferred input device.
- WCAG 1.0 Checkpoint: 11.1.
- WCAG 2.0 Success Criteria: 2.1.1 Keyboard and
- 2.1.3 Keyboard (No Exception)
Mobile Context: Plugin turned off, or not installed, or not available; not compatible with input device (for example, requires mouse).
- MWBP 1.0 Best Practice: OBJECTS_OR_SCRIPT.
Missing or inappropriate page title
User cannot easily scan to get an overview because of missing, inappropriate, or long page title.
Disabilities Context: User who is blind typically uses a screen reader feature to get a list of the currently open windows, by window title. Therefore, if the page title is long, inappropriate or missing, user cannot perceive the content.
- WCAG 1.0 Checkpoint: 13.2.
- WCAG 2.0 Success Criteria: 2.4.2 Page titled.
Mobile Context: Page title truncated to fit narrow viewport of mobile device.
- MWBP 1.0 Best Practice: PAGE_TITLE.
Inconsistency between focus (tab) order and logical document content sequence
User is unable to navigate content in logical sequence, becomes disoriented.
Disabilities Context: User with motor disability uses keyboard for navigation not mouse. User who is blind also often use tab navigation to move from one element to another.
- WCAG 1.0 Checkpoint: 9.4.
- WCAG 2.0 Success Criteria: 2.4.3 Focus order.
Mobile Context: Mobile devices may not have a pointing device so the user may have to navigate elements serially.
- MWBP 1.0 Best Practice: TAB_ORDER.
Non descriptive link label
User cannot determine to follow or not to follow a link because the link label is not descriptive enough.
Disabilities Context: User can not determine purpose of a link when read out of context. User who is blind often accesses a list of links on a page without the context around them.
- WCAG 1.0 Checkpoint: 13.1.
- WCAG 2.0 Success Criteria: 2.4.4 Link Purpose (In Context) and
- 2.4.4 Link Purpose (Link only).
Mobile Context: User can not determine purpose of link.
- MWBP 1.0 Best Practice: LINK_TARGET_ID and LINK_TARGET_FORMAT.
Understandable
Information and the operation of user interface must be understandable.
Experiences discussed below are also available in tabular format.
Long words, long and complex sentences, jargon
User has difficulty understanding information.
Disabilities Context: Users with some types of cognitive disabilities have difficulty processing information. Users who are deaf and whose native language is sign, have difficulty processing complex written language.
- WCAG 1.0 Checkpoint: 14.1.
- WCAG 2.0 Success Criteria: 3.1.5 Reading level.
Mobile Context: Text is displayed in small font, and user is often distracted by ambient conditions (background noise, conversations, moving objects in field of vision).
Content spawning new windows without warning user
User becomes disoriented among windows; back button doesn't work. User closes window, not realizing it is last in stack, closing browser instance.
Disabilities Context: User with low vision, or restricted field of vision, or blindness, or cognitive disabilities doesn't realize active window is new.
- WCAG 1.0 Checkpoint: 10.1.
- WCAG 2.0 Success Criteria: 3.1.2 On focus,
- 3.2.2 On input and
- 3.2.5 Change on request.
Mobile Context: Single window interface. Multiple stacked windows on small screen hide each other.
- MWBP 1.0 Best Practice: POP_UPS.
Blinking, moving, scrolling or auto-updating content
User has difficulty reading and comprehending content.
Disabilities Context: People with reading disabilities, cognitive limitations, and learning disabilities do not have sufficient time to read or comprehend information.
- WCAG 2.0 Success Criteria: 2.2.2 Pause, Stop, Hide and 3.2.5 Change on request.
Mobile Context: Reduced size of mobile viewport or poor ambient lighting makes it difficult to see content. Auto-refreshed pages may also have cost implications if they are left open or put unnoticed into the background.
- MWBP 1.0 Best Practice: AUTO_REFRESH and IMAGES_SPECIFY_SIZE.
Robust
Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.
Experiences discussed below are also available in tabular format.
Invalid or unsupported markup
User cannot access the content because browser or adaptation system chokes on markup or rejects or garbles it.
Disabilities Context: User's assistive technology or browser cannot handle markup.
- WCAG 2.0 Success Criteria: 4.1.1 Parsing.
Mobile Context: Some older mobile browsers do not display content with invalid markup.
- MWBP 1.0 Best Practice: VALID_MARKUP.
Scripting required to generate content
User cannot access the content so loses some information because scripting is not supported by the user agent.
Disabilities Context: User's assistive technology or browser doesn't support scripting.
- WCAG 1.0 Checkpoint: 6.3.
- WCAG 2.0 Success Criteria: Understanding Guideline 4.1
Mobile Context: Scripting turned off or not supported.
- MWBP 1.0 Best Practice: OBJECTS_OR_SCRIPT.