User Agent Accessibility Guidelines 1.0
14 July 2001
This document specifies requirements that, if satisfied by user
agent developers, will lower barriers to accessibility. This
introduction (section 1) provides context for understanding the guidelines
listed in section 2. Section 1
explains the relationship of this document to other accessibility guidelines
published by the Web Accessibility Initiative, which user agents are expected
to conform, known limitations of
this document, and the relationship of this document to other software design
guidelines. Section 3 explains how to make claims that software conforms to these
guidelines and details about the applicability of the requirements for
different kinds of user agents.
"User Agent Accessibility Guidelines 1.0" (UAAG 1.0) is
part of a series of accessibility guidelines published by the Web Accessibility Initiative (WAI). The documents in this
series reflect an accessibility model in which Web content authors, format
designers, and software developers have roles in ensuring that users with
disabilities have access to the Web. These stakeholders intersect and
complement each other as follows:
- Protocol (e.g., HTTP) and content format (e.g., HTML, XML, SVG, etc.)
specifications allow communication on the Web. Format designers include
features that authors should use to create accessible content, and features
that user agents should support through an accessible user interface.
- Authors make use of the accessibility features of different format
specifications, use markup appropriately, write in clear and simple language,
organize a Web site consistently, etc. The "Web Content Accessibility
Guidelines 1.0" [WCAG10] explains the
responsibilities of authors in meeting the needs of users with disabilities. In
User Agent Accessibility Guidelines 1.0, WCAG 1.0 is considered the reference
for what defines accessible Web content. The "Authoring Tool Accessibility
Guidelines 1.0" [ATAG10] explains the
responsibilities of authoring tool developers. An accessible authoring tool
facilitates the creation of accessible Web content and may be operated by users
with disabilities.
- User agent developers design software that conforms to specifications
(including implementation of their accessibility features), provides an
accessible user interface, accessible documentation, and communicates with
other software (notably assistive technologies).
This document explains the responsibilities of user agents in meeting the
needs of users with disabilities. The requirements of this document interact
with those of the "Web Content Accessibility Guidelines 1.0"
[WCAG10] in a number of ways:
- UAAG 1.0 checkpoint 8.1 requires implementation of the accessibility
features of all implemented specifications. Features are those identified as
such and those that satisfy all of the requirements of WCAG 1.0
[WCAG10].
- UAAG 1.0
checkpoint 12.1 requires conformance to WCAG 1.0 for user agent
documentation.
- UAAG 1.0 also incorporates some terms and concepts from WCAG 1.0, a natural
consequence of fact that the documents were designed to complement one
another.
Formats, authors, and designers all have limitations. Formats generally do
not enable authors to encode all of their knowledge in a way that a user agent
can recognize
100%. A format may lack features required for accessibility. An author may not
make use of the accessibility features of a format or may misuse a format
(which can cause problems for user agents). A user agent designer may not
implement a format specification correctly or completely. Some requirements of
this document take these limitations into account.
- UAAG 1.0 includes requirements to satisfy the expectations set by WCAG 1.0
"until user agent" clauses. These clauses make additional requirements of
authors in order to compensate for some limitations of deployed user
agents.
- UAAG 1.0 includes several
repair requirements (e.g., checkpoints checkpoint 2.7 and
checkpoint
2.11) for cases where content does not conform to WCAG 1.0. Furthermore,
this document includes some requirements to address certain widespread
authoring practices that are discouraged because they may cause accessibility
or usability problems (e.g., some uses of HTML frames).
- Except for the indicated repair checkpoints, UAAG 1.0 only requires user
agents to handle what may be
recognized through protocols and formats. For example, user agents
are not expected to recognize that the author has used "clear and simple"
language to express ideas. Please see the section on checkpoint applicability for more
information about what the user agent is expected to recognize.
This document was designed specifically to improve the accessibility of user
agents with multimedia capabilities running in the following type of
environment (typically that of a desktop computer):
- The operating environment includes a keyboard;
- Assistive technologies may be used in the operating environment and may
communicate with the conforming user agent;
This document is not designed so that user agents on other types of
platforms (e.g., handheld devices, kiosks, etc.) will readily conform. This
document does not forbid conformance by any user agent, but some
requirements (e.g., implementation of certain APIs) are not likely to be
satisfied on environments other than the target environment. Future work by the
UAWG may address the accessibility of user agents running on
handheld devices, etc.
The target user agent is one designed for the general public to handle
general-purpose content in ordinary operating conditions. It is expected that a
conforming user agent will typically
consist of a Web browser, one or more media players, and possibly other
components.
This document was designed to improve the accessibility of target user
agents for users with one or more disabilities (including visual, hearing,
physical, and cognitive) in two ways:
- through its own user interface, and
- through other internal facilities, including its ability to communicate
with other technologies (especially assistive
technologies).
Technologies not addressed directly by this document (e.g., those for
braille rendering) will be essential to ensuring Web access for some users with
disabilities. Note that the ability of conforming user agents to communicate
well with assistive technologies will depend in part on the willingness of
assistive technology developers to follow the same standards and conventions
for communication.
This document allows a certain amount of flexibility in the features a user
agent must support in order to conform. For example, some user agents may
conform even though they do not support certain content types (such as video or
audio) or input modalities
(such as mouse or voice). See the section on conformance for more information.
People with (or without) disabilities access the Web with widely varying
sets of capabilities, software, and hardware. Some users with disabilities:
- May not be able to see, hear, move, speak, or may not be able to process
some types of information easily or at all.
- May have difficulty reading or comprehending text.
- May not have or be able to use a keyboard or pointing device.
This document does not include requirements to meet all known accessibility
needs. Some known limitations of this document include the following:
- Input modalities. This document only includes requirements for keyboard,
pointing device, and voice input modalities. This document includes several
checkpoints related to voice input as part of general input requirements (e.g.,
the checkpoints of
guideline 7 and
guideline 11)) but does not otherwise address voice-based navigation or
control. Note: The UAWG intends to
coordinate further work on the topics of voice input and synthesized speech
rendering with groups in W3C's Voice Browser
Activity.
- Output modalities. This document does not include requirements for braille
rendering. Some requirements are specific to graphical rendering and others
specific to synthesized speech rendering (speech rendering requirements are
made by
checkpoint 4.12 to checkpoint 4.16). Many of the requirements of this document
are generic enough to apply to any output modality (including braille). User
agents conform to this document by
supporting some combination of graphical and audio/speech rendering output; see
the section on content type
labels for more information.
- Size and color of non-text content. This document includes some checkpoints
to ensure that the user is able to control the size and color of visually
rendered text content (checkpoints 4.1 and 4.3). This
document does not in general address control of the size and color of visually
rendered non-text
content. Note: Resizing capabilities may be
required for conformance to other specifications (e.g., SVG
[SVG]).
- Background image interference. The requirement of
checkpoint 3.1 to allow the user to turn off rendering of background images
does not extend to multi-layered rendering.
- User control of every user interface component. This document includes some
requirements for user control of user interface components that may be changed
through content (see guideline 5). However, these requirements do not account for
every user interface component that the author may affect (e.g., the author
might supply a script that causes text to scroll in the status bar). User
agents are required to follow software usability guidelines (see checkpoint 7.3),
which are also expected to include requirements for user control over user
interface behavior. Note. It is more difficult for users to
distinguish content from user interface when both are rendered as sound in one
dimension, than it is when both are rendered visually in two dimensions.
Developers of aural user agents are therefore strongly encouraged to apply the
requirements of this document to both content and user agent components.
- Time. This document includes requirements for control of some time
parameters (including checkpoint 2.4, checkpoint 4.4,
checkpoint
4.5, and checkpoint 4.12). The requirements are for time parameters
that the user agent recognizes and controls. This document does not include
requirements for control of time parameters managed on the server.
- Security. This document does not address security issues that may arise as
a result of these requirements. For instance, requirements that software be
able to read and write content and user interface information through APIs
raise security issues. See the section on restricted functionality and
conformance.
- Intellectual property. This document does not address intellectual property
issues that may arise as a result of these requirements.
Note: The User Agent Accessibility Guidelines Working Group
may address these topics in a future version of the User Agent Accessibility
Guidelines. Even though UAAG 1.0 does not address these
topics, user agent developers are encouraged to consider them in their
designs.
Considerable effort has been made to ensure that the requirements of this
document are compatible with other good software design practices. However,
this document does not purport to be a complete guide to good software design.
For instance, the general topic of user interface design for computer software
exceeds the scope of this document, though some user interface requirements
have been included because of their importance to accessibility. The
"Techniques for User Agent Accessibility Guidelines 1.0"
[UAAG10-TECHS] includes some references to general software design
guidelines and platform-specific accessibility guidelines (see checkpoint 7.3).
Involving people with disabilities in the design and testing of software will
generally improve the accessibility of the software.
Installation is an important aspect of both accessibility and general
software usability. On platforms where a user can install a user agent, the
installation (and update) procedures need to be accessible. This document does
not include a checkpoint requiring that installation procedures be accessible.
Since this document considers installation to be part of software usage, the
different aspects of installation (user interface, documentation,
operating environment conventions, etc.) are already covered by the
complete set of checkpoints.
Many users without disabilities are likely to benefit from the requirements
developed to benefit users with disabilities. For example, users without
disabilities:
- may have a text-only screen, a small screen, or a slow Internet connection
(e.g., via a mobile phone browser). These users are likely to benefit from the
same features that provide access to people with low vision or blindness.
- may be in a situation where their eyes, ears, or hands are busy or
interfered with (e.g., driving to work, working in a noisy environment, etc.).
These users are likely to benefit from the same features that provide access to
people who cannot use a mouse or keyboard due to a visual, hearing, or physical
disability.
- may not understand fluently the natural language of spoken content. These
users are likely to benefit from the same visual rendering of text
equivalents that make spoken language accessible to people with a
hearing disability.
Software that satisfies the requirements of this document is expected to be
more flexible, manageable, extensible, and beneficial to all users. For
example, a user agent architecture that allows programmatic access to
content and the user
interface will encourage software modularity and reuse, and will
enable operation by scripting tools and automated test engines in addition to
assistive technologies.