This document, “Mobile Accessibility: How WCAG 2.0 and Other W3C/WAI Guidelines Apply to Mobile” describes how the Web Content Accessibility Guidelines (WCAG) 2.0 [[WCAG20]] and its principles, guidelines, and success criteria can be applied to mobile web content, mobile web apps, native apps, and hybrid apps using web components inside native apps. It provides informative guidance, but does not set requirements. It also highlights the relevance of the User Agent Accessibility Guidelines 2.0 [[UAAG20]] in the mobile context.
This document is intended to become a Working Group Note and is part of a series of technical and educational documents published by the W3C Web Accessibility Initiative (WAI).
This document is an Editor's Draft being developed by the Mobile Accessibility Task Force (Mobile A11Y TF) operating under the terms of its Work Statement under the joint coordination and review of the Web Content Accessibility Guidelines Working Group (WCAG WG) and the User Agent Accessibility Guidelines Working Group (UAWG), which is part of the Web Accessibility Initiative (WAI) of the World Wide Web Consortium (W3C).
WCAG 2.0 is a stable web standard. Comments on this document will not affect WCAG 2.0 wording.
Publication as an Editors' Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. This document should always be cited as a work in progress.
This document provides informative guidance (but does not set requirements) with regard to interpreting and applying Web Content Accessibility Guidelines (WCAG) 2.0 [WCAG20] to web and non-web mobile content and applications.
While the World Wide Web Consortium (W3C)'s W3C Web Accessibility Initiative (WAI) is primarily concerned with web technologies, its guidance is also relevant to non-web technologies. The W3C-WAI has published the Note Guidance on Applying WCAG 2.0 to Non-Web Information and Communications Technologies (WCAG2ICT) to provide authoritative guidance on how to apply WCAG to non-web technologies such as mobile native applications. The current document is a mobile-specific extension of this effort.
W3C Mobile Web Initiative Recommendations and Notes pertaining to mobile technologies also include the Mobile Web Best Practices and the Mobile Web Application Best Practices. These offer general guidance to developers on how to create content and applications that work well on mobile devices. The current document is focused on the accessibility of mobile web and applications to people with disabilities and is not intended to supplant any other W3C work.
"Mobile" is a generic term for a broad range of wireless devices and applications that are easy to carry and use in a wide variety of settings, including outdoors. Mobile devices range from small handheld devices (e.g. feature phones, smartphones) to somewhat larger tablet devices. The term also applies to "wearables" such as "smart"-glasses, "smart"-watches and fitness bands, and is relevant to other small computing devices such as those embedded into car dashboards, airplane seatbacks, and household appliances.
While mobile is viewed by some as separate from "desktop/laptop", and thus perhaps requiring new and different accessibility guidance, in reality there is no absolute divide between the categories. For example:
Furthermore, the vast majority of user interface patterns from desktop/laptop systems (e.g. text, hyperlinks, tables, buttons, pop-up menus, etc.) are equally applicable to mobile. Therefore, it's not surprising that a large number of existing WCAG 2.0 techniques can be applied to mobile content and applications (see Appendix A). Overall, WCAG 2.0 is highly relevant to both web and non-web mobile content and applications.
That said, mobile devices do present a mix of accessibility issues that are different from the typical desktop/laptop. The "Discussion of Mobile-Related Issues" section that follows, explains how these issues can be addressed in the context of WCAG 2.0 as it exists or with additional best practices. All of the advice in this document can be applied to mobile web sites, mobile web applications, and hybrid web-native applications. Most of the advice also applies to native applications (also known as "mobile apps").
Note: WCAG 2.0 does not provide testable success criteria for some of the mobile-related issues. The work of the Mobile Accessibility Task Force has been to develop techniques and best practices in these areas. When the techniques or best practices don't map to specific WCAG success criteria, they aren't given a sufficient, advisory or failure designation. This doesn't mean that they are optional for creating accessible web content on a mobile platform, but rather that they cannot currently be assigned a designation. The Task Force anticipates that some of these techniques will be included as sufficient or advisory in a potential future iteration of WCAG.
The current document references existing WCAG 2.0 Techniques that apply to mobile platform (see Appendix A) and provides new best practices, which may in the future become WCAG 2.0 Techniques that directly address emerging mobile accessibility challenges such as small screens, touch and gesture interface, and changing screen orientation.
The User Agent Accessibility Guidelines (UAAG) 2.0 [UAAG2] is meant for the developers of user agents (e.g. web browsers and media players), whether for desktop/laptop or mobile operating systems. A user agent that follows UAAG 2.0 will improve accessibility through its own user interface, through options it provides for rendering and interacting with content, and through its ability to communicate with other technologies, including assistive technologies.
To assist developers of mobile browsers, the UAAG 2.0 Reference support document contains numerous mobile examples. These examples are also available in a separate list of mobile-related examples, maintained by the User Agent Accessibility Guidelines Working Group (UAWG).
The Authoring Tool Accessibility Guidelines (ATAG) 2.0 [ATAG2] provides guidelines for the developers of authoring tools, whether for desktop/laptop or mobile operating systems. An authoring tool that follows ATAG 2.0 will be both more accessible to authors with disabilities (Part A) and designed to enable, support, and promote the production of more accessible web content by all authors (Part B).
To assist developers of mobile authoring tools, the Implementing ATAG 2.0 support document contains numerous mobile authoring tool examples.
One of the most common characteristics of mobile devices is the small size of their screens. This limited size places practical constraints on the amount of information that can be effectively perceived by users at any one time, even when high screen resolution might enable large amounts of information to be rendered. The amount of information that can be displayed is even further limited when magnification is used, for example by people with low vision. See 2.2 Zoom/Magnification.
Some best practices for helping users to make the most of small screens include
A variety of methods allow users to control content size on mobile devices with small screens. Some of these features are targeted at all users (e.g. browser “pinch zoom” features), while others tend to be made available as "accessibility features" targeted at people with visual or cognitive disabilities.
Note on reflow: There are important accessibility differences between zoom/magnification features that horizontally reflow content, especially text, and those that do not. When text content is not reflowed, users must pan back and forth as they read each line.
Zoom/Magnification features include the following:
The WCAG 2.0 success criterion that is most related to zoom/magnification is
SC 1.4.4 requires text to be resizable without assistive technology up to at least 200 percent. To meet this requirement content must not prevent text magnification by the user.
Some methods for supporting magnification/zoom include:
Accessibility features geared toward specific populations of people with disabilities fall under the definition of assistive technology adopted by WCAG and thus cannot be relied upon to meet success criterion 1.4.4. For example, an OS-level zoom feature that magnifies all platform content and has features to specifically support people with low vision is likely considered an assistive technology.
Mobile devices are more likely than desktop/laptop devices to be used in varied environments including outdoors, where glare from the sun or other strong lighting sources is more likely. This scenario heightens the importance of use of good contrast for all users and may compound the challenges that users with low vision have accessing content with poor contrast on mobile devices.
The WCAG 2.0 success criteria related to the issue of contrast are:
SC 1.4.3. allows for different contrast ratios for large text. Allowing different contrast ratios for larger text is useful because larger text with wider character strokes is easier to read at a lower contrast. This allows designers more leeway for contrast of larger text, which is helpful for content such as titles. The ratio of 18-point text or 14-point bold text described in the SC 1.4.3 was judged to be large enough to enable a lower contrast ratio for web pages displayed on a 15-inch monitor at 1024x768 resolution with a 24-inch viewing distance. Mobile device content is viewed on smaller screens and in different conditions so this allowance for lessened contrast on large text must be considered carefully for mobile apps.
For instance, the default text size for mobile platforms might be larger than the default text size used on non-mobile devices. When determining which contrast ratio to follow, developers should strive to make sure to apply the lessened contrast ratio only when text is roughly equivalent to 1.2 times bold or 1.5 times (120% bold or 150%) that of the default platform size. Note, however, that the use of text that is 1.5 times the default on mobile platforms does not imply that the text will be readable by a person with low vision. People with low vision will likely need and use additional platform level accessibility features and assistive technology such as increased text size and zoom features to access mobile content.
With limited screen “real estate” but a variety of gesture options available, mobile developers have experimented with a variety of screen layouts beyond the conventional web paradigm in which the user begins at the “top” and generally works down. Some mobile layouts start the user somewhere in the “middle” and provide highly dynamic visual experiences in which new content may be pulled in from any direction or the user’s point of regard may shift in various directions as previously off-screen content is brought on-screen.
Such user interfaces can be disorienting when the only indicators of the state of the user interface and what is happening in response to user actions are visual.
The WCAG 2.0 success criterion related to the issue of non-linear layouts is:
Mobile device design has evolved away from built-in physical keyboards (e.g. fixed, slide-out) towards devices that maximize touchscreen area and display an on-screen keyboard only when the user has selected a user interface control that accepts text input (e.g. a textbox).
However, keyboard accessibility remains as important as ever. WCAG 2.0 requires keyboard control at Level A and keyboard control is supported by most major mobile operating systems via keyboard interfaces, which allow mobile devices to be operated using external physical keyboards (e.g. keyboards connected via Bluetooth, USB On-The-Go) or alternative on-screen keyboards (e.g. scanning on-screen keyboards).
Supporting these keyboard interfaces benefits several groups with disabilities:
Several WCAG 2.0 success criteria are relevant to effective keyboard control:
The high screen resolution of mobile devices means that many interactive elements can be shown together on a small screen. But these elements must be big enough and have enough distance from each other so that users can safely target them by touch.
Best practices for touch target size include the following:
Note: Screen magnification should not need to be used to obtain this size, because magnifying the screen often introduces the need to pan horizontally as well as vertically, which can decrease usability.
Many mobile devices are designed to be primarily operated via gestures made on a touchscreen. These gestures can be simple, such as a tap with one finger, or very complex, involving multiple fingers, multiple taps and drawn shapes.
Some (but not all) mobile operating systems provide work-around features that let the user simulate complex gestures with simpler ones using an onscreen menu.
Some best practices when deciding on touchscreen gestures include the following:
Technique M003 - Activating elements via the click event
Another issue with touchscreen gestures is that they might lack onscreen indicators that remind people how and when to use them. For example, a swipe in from the left side of the screen gesture to open a menu is not discoverable without an indicator or advisement of the gesture. See 4.6 Provide instructions for custom touchscreen and device manipulation gestures.
Note: While improving the accessibility of touchscreen gestures is important, keyboard accessibility is still required by some users and to meet WCAG 2.0. See 3.1 Keyboard Control for Touchscreen Devices.
In addition to touchscreen gestures, many mobile operating systems provide developers with control options that are triggered by physically manipulating the device (e.g. shaking or tilting). While device manipulation gestures can help developers create innovative user interfaces, they can also be a challenge for people who have difficulty holding or are unable to hold a mobile device.
Some (but not all) mobile operating systems provide work-around features that let the user simulate device shakes, tilts, etc. from an onscreen menu.
Therefore, even when device manipulation gestures are provided, developers should still provide touch and keyboard operable alternative control options. See 3.1 Keyboard Control for Touchscreen Devices.
Another issue with control via device manipulation gestures is that they might lack onscreen indicators that remind people how and when to use them. See Touchscreen gesture instructions. See 4.6 Provide instructions for custom touchscreen and device manipulation gestures.
Mobile sites and applications should position interactive elements where they can be easily reached when the device is held in different positions.
When designing mobile web content and applications many developers attempt to optimize use with one hand. This can benefit people with disabilities who may only have one hand available, however, developers should also consider that an easy-to-use button placement for some users might cause difficulties for others (e.g. left- vs. right-handed use, assumptions about thumb range of motion). Therefore, flexible use should always be the goal.
Some (but not all) mobile operating systems provide work-around features that let the user temporarily shift the display downwards or sideways to facilitate one-handed operation.
Some mobile applications automatically set the screen to a particular display orientation (landscape or portrait) and expect that users will respond by rotating the mobile device to match. However, some users have their mobile devices mounted in a fixed orientation (e.g. on the arm of a power wheelchair).
Therefore, mobile application developers should try to support both orientations. If it is not possible to support both orientations, developers should ensure that it is easy for all users to change the orientation to return to a point at which their device orientation is supported.
Changes in orientation must be programmatically exposed to ensure detection by assistive technology such as screen readers. For example, if a screen reader user is unaware that the orientation has changed the user might perform incorrect navigation commands.
Components that are repeated across multiple pages should be presented in a consistent layout. In responsive web design, where components are arranged based on device size and screen orientation, web pages within a particular view (set size and orientation) should be consistent in placement of repeated components and navigational components. Consistency between the different screen sizes and screen orientations is not a requirement under WCAG 2.0.
The WCAG 2.0 success criteria that are most related to the issue of consistency are:
The small screen size on many mobile devices limits the amount of content that can be displayed without scrolling.
Positioning important page information so it is visible without requiring scrolling can assist users with low vision and users with cognitive impairments.
If a user with low vision has the screen magnified only a small portion of the page might be viewable at a given time. Placing important elements before the page scroll allows those who use screen magnifiers to locate important information without having to scroll the view to move the magnified area. Placing important elements before the page scroll also makes it possible to locate content without performing an interaction. This assists users that have cognitive impairments such as short-term memory disabilities. Placing important elements before the page scroll also helps ensure that elements are placed in a consistent location. Consistent and predictable location of elements assists people with cognitive impairments and low vision.
When multiple elements perform the same action or go to the same destination (e.g. link icon with link text), these should be contained within the same actionable element. This increases the touch target size for all users and benefits people with dexterity impairments. It also reduces the number of redundant focus targets, which benefits people using screen readers and keyboard/switch control.
The WCAG 2.0 success criterion that is most related to grouping of actionable elements is:
For more information on grouping operable elements, see H2: Combining adjacent image and text links for the same resource technique.
Elements that trigger changes should be sufficiently distinct to be clearly distinguishable from non-actionable elements (content, status information, etc.). Providing a clear indication that elements are actionable is relevant for web and native mobile applications that have actionable elements like buttons or links, especially in interaction modes where actionable elements are commonly detected visually (touch and mouse use). Interactive elements must also be detectable by users who rely on a programmatically determined accessible name (e.g. screen reader users).
Visual users who interact with content using touch or visual cursors (e.g. mice, touchpads, joysticks) should be able to clearly distinguish actionable elements such as links or buttons. Existing interface design conventions are aimed at indicating that these visual elements are actionable. The principle of redundant coding ensures that elements are indicated as actionable by more than one distinguishing visual feature. Following these conventions benefits all users, but especially users with vision impairments.
Visual features that can set an actionable element apart include shape, color, style, positioning, text label for an action, and conventional iconography.
Examples of distinguishing features:
The WCAG 2.0 success criteria do not directly address issue of clear visual indication that elements are actionable but are related to the following success criteria:
The ability to provide control via custom touchscreen and device manipulation gestures can help developers create efficient new interfaces. However, for many people, custom gestures can be a challenge to discover, perform and remember.
Therefore, instructions (e.g. overlays, tooltips, tutorials, etc.) should be provided to explain what gestures can be used to control a given interface and whether there are alternatives. To be effective, the instructions should, themselves, be easily discoverable and accessible. The instructions should also be available anytime the user needs them, not just on first use, though on first use they may be made more apparent through highlighting or some other mechanism.
These WCAG 2.0 success criteria are relevant to providing instructions for gestures:
On some mobile devices, the standard keyboard can be customized in the device settings and additional custom keyboards can be installed. Some mobile devices also provide different virtual keyboards depending on the type of data entry. This can be set by the user or can be set to a specific keyboard. For example, using the different HTML5
input types - such as
<input type="tel"> (see HTML5: States of the
type attribute) - on a website will show different keyboards automatically when users are entering information into that field. Setting the type of keyboard helps prevent errors and ensures formats are correct but can be confusing for people who are using a screen reader when there are subtle changes in the keyboard.
Users can enter information on mobile devices in multiple ways such as on-screen keyboard, Bluetooth keyboard, touch, and speech. Text entry can be time-consuming and difficult in certain circumstances. Reduce the amount of text entry needed by providing select menus, radio buttons, check boxes or by automatically entering known information (e.g. date, time, location).
Mobile devices provide many features to help users with disabilities interact with content. These include platform characteristics such as zoom, larger fonts, and captions. The features and functions available differ depending on the device and operating system version. For example, most platforms have the ability to set large fonts, but not all applications honor it for all text. Also, some applications might increase font size but not wrap text, causing horizontal scrolling.
WCAG 2.0 Techniques that Apply to Mobile
UAAG Mobile Accessibility Examples