EPUB Accessibility Techniques defines discovery and content accessibility requirements for EPUB®
Publications.
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document.
This document, EPUB Accessibility Techniques, provides guidance on how to meet the
[EPUB-A11Y-11] discovery and accessibility requirements for EPUB Publications.
This document does not cover techniques and best practices already addressed in [WCAG2] and
[WAI-ARIA-1.1] for which no substantive differences in application exist.
1.2 Terminology
This document uses the following terminology defined in EPUB 3 [EPUB-3]:
An assistive technology is not always a separate application from a Reading System. Reading
Systems often integrate features of standalone assistive technologies, such as text-to-speech
playback.
2. About the Techniques
The accessibility techniques described in this document are advisory in nature. They are intended to help
EPUB Creators create EPUB Publications that conform to the requirements in [EPUB-A11Y-11], but they
are not all applicable in all situations and there may be other ways to meet the requirements of that
specification. As a result, this document should not be read as providing prescriptive requirements.
These techniques also do not address issues in digital publishing for which no universally accessible
solutions exist. The W3C's Digital Publishing Interest Group has published a note that outlines many of
these issues [DPUB-Accessibility]. As solutions become available, they will be incorporated into the
appropriate document, whether this one or one it refers to.
If EPUB Creators encounter issues that are not covered in these or related techniques, they are
encouraged to report the issue to the appropriate community for guidance on how to meet accessibility
standards. The W3C Web Accessibility Interest Group has a
public mailing list where issues meeting [WCAG2] and [WAI-ARIA-1.1] requirements can be raised. The
W3C Publishing Community Group issue
tracker can be used to ask for support implementing EPUB-specific requirements and the EPUB 3 Working Group's issue tracker to report
issues with this document.
3. Discovery Metadata Techniques
3.1 Identify primary access modes
An access mode is defined as a "human sense perceptual system or cognitive faculty through which a
user may process or perceive the content of a digital resource." [ISO24751-3] For example, if an
EPUB Publication contains images and video, visual perception is required to consume the content
exactly as it was created.
There are four access modes that are typically specified for EPUB Publications:
textual — the publication contains text content (headings, paragraphs,
etc.).
visual — the publication contains visual content such as images, graphics,
diagrams, animations, and video.
auditory — the publication contains auditory content such as standalone
audio clips and audio soundtracks for video content.
tactile — the publication contains tactile content such as embedded braille
and tactile diagrams.
For a user to determine whether an EPUB Publication is suitable for their needs, they need to know
which of these access modes are required to consume the content. List all applicable access modes in
the [schema-org] accessMode property,
repeating the property for each applicable mode.
Note that the access modes of the content do not reflect any adaptations that have been provided. For
example, if a comic book also includes alternative text for each image, it does not have a textual
access mode. See the following section on sufficient access modes for how to
indicate that the available adaptations allow the content to be consumed in another mode.
The access modes sufficient to consume an EPUB Publication express a broader picture of the potential
usability than do the basic access modes. Where the basic access modes
identify the default nature of the media used in the publication, sufficient access modes identify
which modes, or sets of modes, a user requires to read the publication. Sufficient access modes
account for the affordances and adaptations that have been provided, allowing a user to determine
whether the content will be usable regardless of its default nature.
For example, consider an EPUB Publication that contains graphics and charts, as well as descriptions
for all these images. The publication has both textual and visual content, so the EPUB Creator will
include the following metadata entries to indicate this:
This metadata does not make clear whether a textual access mode is sufficient to read the entire
publication, or whether a visual one is, only that two modes are required by default. This
discrepancy is why sufficiency is also important to know.
The first set of sufficiency metadata the EPUB Creator inputs will establish the textual and visual
requirement:
The order in which the access modes are listed is not important. The only requirement is that they be
separated by commas.
Since the EPUB Creator has also included descriptions for all the images, the EPUB Creator can also
indicate that a purely textual access mode is sufficient to read the content:
Without this metadata, users would not have known that they could read the publication only via its
text content.
Note
A sufficient access mode of "visual" is not provided as the content is not entirely
image-based. Textual content is considered a separate mode as it can be read both visually and
aurally (text-to-speech). Photo books without text would be examples of works with a purely
visual sufficient access mode.
The full set of entries in this example is as follows:
Note that sufficiency of access is often a subjective determination of the EPUB Creator based on
their understanding of what information is essential to comprehending the text. Some information
loss occurs by not being able to view a video, for example, but the EPUB Creator might regard the
visual or auditory losses as inconsequential if a transcript provides all the necessary information
to understand the concepts being conveyed.
The accessModeSufficient property, as defined in [schema-org], allows more
complicated expressions than can be represented in the EPUB 2 or 3 Package Document (e.g.,
definition of lists of values and inclusion of a human-readable description). A future version
of EPUB might allow for richer metadata, but the basic expression shown in this section is
sufficient for discovery purposes.
3.3 Identify accessibility features
Identifying all the accessibility features and adaptations included in an EPUB Publication allows
users to determine whether the content is usable at a more fine-grained level than the access modes
do.
For example, a math textbook might have a textual access mode, but that alone does not indicate
whether MathML markup is available. Whether a visual work only provides alternative text or whether
it includes extended descriptions is also important to know when gauging its usability.
The EPUB format requires that some accessibility features will always be present (e.g., a table of
contents). Do not exclude these features from the accessibility metadata, as users typically are not
aware what features are built into a format. Failing to include entries will reduce the
discoverability of the publication when users search for specific features.
There are three widely recognized hazards that can affect readers of digital content:
flashing — if a resource flashes more than three times a second, it can cause seizures (e.g.,
videos and animations). See also [WCAG2] Guideline
2.3.
motion simulation — if a resource simulates motion, it can cause a user to become nauseated
(e.g., a video game drawn on the [HTML] canvas element or parallax scrolling with CSS).
sound — certain sound patterns, such as ringing and buzzing, can cause seizures, while loud
or sudden changes in volume can also negatively affect users.
EPUB Creators have to report whether their EPUB Publications contain resources that present any of
these hazards to users, as they can have real physical effects.
Note
What precisely constitutes a sound hazard, and how to test for these hazards, is not standardized
as of publication of this document. EPUB Creators will have to use their discretion on when to
specify a sound hazard until additional guidance is developed. This technique will be updated
whenever there is more clarity on this issue.
Unlike other accessibility properties, the presence of hazards can be expressed both positively and
negatively. This design decision was made because users most often search for content that is free
from hazards that affect them, but also want to know what dangers are present in any publications
they discover.
Do not skip reporting hazards just because an EPUB Publication does not contain any content that
could present risks. Users cannot infer a meaning when no metadata is present. The value
"none" can be used in such cases instead of repeating each non-hazard.
If an EPUB Publication contains a hazard, provide additional information about its source and nature
in the accessibility summary.
If hazards cannot be definitively determined, report the value "unknown".
An accessibility summary provides a brief, human-readable description of the accessibility
characteristics of an EPUB Publication, or lack thereof.
If an EPUB Publication does not meet the requirements for content accessibility in [EPUB-A11Y-11],
the reason(s) it fails should be noted in the summary.
Do not repeat this property unless it contains the summary in another language. In the case of
multiple summaries, use the xml:lang attribute to differentiate the language.
The use of the schema:accesibilityAPI property is no longer necessary for EPUB
Publications. EPUB Creators are not responsible for the interaction between Reading Systems and the
underlying platform APIs.
Meeting the requirements of [WCAG2] is a better measure of the accessibility of scripting, as this
property does not differentiate between ARIA markup used for document structure or for identifying
controls.
3.7 Identify Input Control Methods
The use of the schema:accesibilityControl property is no longer necessary for EPUB
Publications. This property does not differentiate issues arising from the Reading System interface
from those in the underlying content, which has led to confusion about its use.
Meeting the requirements of [WCAG2] will mitigate most known issues with the content and is
sufficient for authoring purposes.
3.8 Examples
The following examples show the metadata that would be added to an EPUB Publication that has textual
and visual access modes, is sufficient for reading by text, contains alternative text and MathML
markup, and has a flashing hazard.
4. WCAG Techniques
4.1 General Guidance
Techniques for meeting the requirements of the [WCAG2] are defined in Techniques for WCAG. This document does not
repeat those techniques.
In general, the differences between the application of WCAG techniques to Web pages and their
application to EPUB Content Documents is minimal, but the following sections outline some key
differences.
One point to note is that the WCAG techniques cover a greater range of technologies and content types
than are typically found in an EPUB Publication, so many are not applicable.
The following sets of techniques are the most applicable to EPUB Content Documents:
Other techniques will apply depending on the technologies used (e.g., a [SWF] video in EPUB 2) or
any alternative formats embedded in the EPUB Publication (e.g., a PDF form).
4.1.1 Helpful Resources
EPUB Creators not familiar with the [WCAG2] may find the number of techniques daunting, as they
are intended to provide broad coverage of possible solutions.
Assistance applying these techniques to EPUB Content Documents is available from the following
sources:
4.2.1 Ensure meaningful order of content across spreads
[WCAG2] Success Criterion 1.3.2
specifies that each Web page have a meaningful order (i.e., that the visual presentation of the
content match the underlying markup).
As EPUB allows two documents to be rendered together in a synthetic spread [EPUB-3], the order of
content within a single document cannot always be evaluated in isolation. Content may span
visually from one document to the next. For example, a sidebar might span the bottom of two
pages.
Ordering each document separately by the visual display will lead to users of assistive
technologies encountering gaps between the start and end of the spanned text. If the markup
cannot be arranged to provide a more logical reading experience (e.g., the beginning of the
spanned content at the end of the first page followed by the conclusion at the start of the
next), another means of satisfying this criteria will be necessary to avoid failure (e.g., a
hyperlink could be provided to allow a user to jump from the break point on the first page to
the continuation on the next).
The reason an EPUB Publication passes by meeting these requirements has to do with differences in
how a user interacts with the set of documents in an EPUB Publication. In particular, although
an EPUB Publication typically consists of many Content Documents, Reading Systems automatically
provide the ability for the user to move seamlessly from one document to the next, so long as
they are listed in the spine [EPUB-3]. To the user, an EPUB Publication is a single document they have complete
access to, not a set of disconnected pages that they need links to move through.
The required table of contents provides a second method to access the major headings of the
publication. The user can jump to any heading and continue to navigate from there, regardless of
how the publication is chunked.
Following these two requirements therefore satisfies the need for multiple ways to access the
content. Reading Systems also typically provide search capabilities, something the EPUB Creator
cannot provide, so users also have a third option available in most cases.
Although EPUB Creators only need to follow EPUB requirements to meet this criterion, they are
still encouraged to provide additional methods to improve access beyond the minimum. Some
suggestions include:
adding at least one link to every Content Document in the spine to the table of contents,
when feasible;
adding an index to locate major topics; and
adding additional navigation aids to the EPUB Navigation Document (e.g., lists of figures
and tables).
4.2.2.1 Note About the Table of Contents
A common question about the EPUB table of contents is what completeness it needs to have with
respect to the headings of the publication. Although the obvious answer seems like it should
be a simple aggregation of all headings for all sections, practically there are several
usability challenges to this approach.
Factors such as device screen sizes can make the table of contents for publications with a
deep hierarchy of headings unreadable, so EPUB Creators will trim headings below a certain
depth to improve the readability. Further, Reading Systems do not always provide structured
access to the headings in the table of contents, or provide shortcuts to navigate the links.
The result is that users have to listen to each link one at a time to find where they want
to go, a tedious and time-consuming process.
Although it is expected that Reading Systems will improve access to the table of contents as
accessibility support for EPUB evolves — making complete tables of contents usable by
everyone — there are legitimate usability reasons why they are not provided now.
When EPUB Creators choose not to provide links to all the headings, however, they should
optimize the linking they do provide for the best overall reading experience. Some
considerations on how to achieve this include:
ensuring that there is at least one link to every EPUB Content Document — allowing
the user to reach each document simplifies navigation to the minor headings within
them; and
only omitting minor headings from the table of contents — although a subjective
decision, there is often a level of diminishing value for navigation (e.g., fourth
level and lower headings often only delimit short subsections on a topic).
4.2.3 Ensure the order of table of contents entries matches linear order
The table of contents provides users more than just links into the content. It is also a means to
understand the structure and ordering of an EPUB Publication. Consequently, users may have
difficulty locating where they are in a publication, where they want to go, and also how to
return to previous locations when the order of entries in the table of contents does not match
the linear reading order.
EPUB Creators should therefore ensure that the entries in the table of contents always match the
linear order of the content. Specifically, the order of entries should reflect both:
the order of EPUB Content Documents in the spine; and
the order of each referenced section within its respective Content Document.
Only if there is a logical case for an alternative arrangement of entries should the ordering
differ. Such scenarios typically only occur when the content does not have to be read linearly
or when additional information is included at the end of a table of contents. For example, the
table of contents for a magazine might be ordered to list all the major articles first, followed
by features, etc.
When the ordering of the table of contents does not match the content, EPUB Creators should
include an explanation why in the accessibility summary.
EPUB Creators should avoid including links to supplementary content at the end of the table of
contents. Links to figure, tables, illustrations and similar content is better included as a
separate navigation elements (either in the EPUB Navigation Document or in the spine). EPUB
Creators can include links to these additional navigation lists in the table of contents.
4.3 Semantics
4.3.1 ARIA roles and epub:type
Note
The following guidance is only for EPUB Content Documents. The type attribute is
the only means of adding structural information to Media Overlay Documents so that features
like lists and tables can be navigated more efficiently. It is also required in the EPUB
Navigation Document to identify key structures.
Although the role attribute may seem similar in nature to the type attribute [EPUB-3], their target uses in EPUB Content Documents do not
overlap.
The key difference between these attributes is that the role attribute bridges
accessibility in content while the type attribute provides hooks to enable Reading
System behaviors. Omitting roles lessens the accessibility for users of Assistive Technologies,
in other words, while omitting types diminishes certain functionality in Reading Systems (e.g.,
pop-up footnotes or special presentations of the content).
Since each attribute offers different advantages, it is not necessary that they be used together.
Due to the lack of restrictions on where EPUB Creators can use the type attribute,
pairing the attributes may cause accessibility issues (e.g., putting roles on the [HTML]
body element).
In particular, the use of the type attribute is not a means of satisyfing
requirements for ARIA roles in WCAG.
For EPUB Creators looking to move from the type attribute to using ARIA roles, the
EPUB Type to ARIA Role
Authoring Guide guide details notable authoring differences between the two attributes.
It also includes a mapping table of semantics in the EPUB Structural Semantics Vocabulary to
equivalent ARIA roles in [DPUB-ARIA-1.0] and [WAI-ARIA-1.1].
4.3.2 Do not repeat semantics across chunked content
Although EPUB Publications appear as single contiguous documents to users when read, they are
typically composed of many individual EPUB Content Documents. This practice keeps the amount of
markup that has to be rendered small to reduce the load time in Reading Systems (i.e., to
minimize the time the user has to wait for a document to appear). It is rare, at least for
books, for an EPUB Publication to contain only one Content Document with all the content in
it.
When content is chunked in this way, it often requires the EPUB Creator to make decisions about
how best to restructure the information. A part, for example, will typically not include all the
chapters that belong to it. The EPUB Creator will instead separate the part heading from each
chapter, putting each into a separate document.
Although visually these restructuring decisions can be hidden from readers, they impact the
functionality of Assistive Technologies. In the case of [WAI-ARIA-1.1] roles, the result is
that only the subset present in the currently-loaded EPUB Content Document are exposed to users.
An Assistive Technology cannot provide a list of landmarks for the whole publication, as it
cannot see outside the current document.
To counteract this destructuring effect, EPUB Creators sometimes think to re-add or re-identify
structures in the belief that having this information in every document will be helpful to users
(e.g., adding an extra [HTML] section element around a chapter to indicate it
belongs to a part, or putting the part semantic on the body tag). All this practice
does, however, is add repetition that is not only disruptive when reading but can make the
structure of the publication harder to follow. EPUB Creators are therefore advised not to
attempt to rebuild structures in these ways.
For example, consider a book that has five parts and each part contains five chapters.
Structurally, each chapter belongs to its part (i.e., is grouped with it), as in the following
markup:
Since this would lead to a large content file, the part heading is typically split out into its
own Content Document so that it will appear on its own page:
Doing so introduces a new part landmark into each document, which will cause an
Assistive Technology to inform the user that the landmark is available to navigate to.
4.3.3 Include EPUB landmarks
[WAI-ARIA-1.1] landmarks are
similar in nature to EPUB
landmarks [EPUB-3]: both are designed to provide users with quick access to the major
structures of a document, such as chapters, glossaries and indexes. ARIA landmarks are compiled
automatically by Assistive Technologies from the roles that have been
applied to the markup, so EPUB Creators only need to follow the requirement to include roles for
the landmarks to be made available to users.
Although automatic generation of ARIA landmarks simplifies authoring, it also means that ARIA
landmarks are limited to how the EPUB Publication has been chunked up into Content Documents. An
Assistive Technology can only present the landmarks available in the currently-loaded document;
it cannot provide a complete picture of all the landmarks in a multi-document publication (see
the previous section for more discussion about content chunking).
EPUB landmarks, on the other hand, are compiled by the EPUB Creator prior to distribution, and
are not directly linked to the use of the type attribute [EPUB-3] in the content. They are designed to simplify
linking to major sections of the publication in a machine-readable way, as Reading Systems do
not scan the entire publication for landmarks, either. EPUB landmarks are typically not as
numerous as ARIA landmarks, as Reading Systems only expose so many of these navigation aids.
Given these differences in application, however, it is important to include EPUB landmarks and
not rely only on the presence of ARIA roles to facilitate navigation, and vice versa. Each aids
navigation in its own way.
The EPUB specification does not require that EPUB Creators include a specific set of landmarks,
but it is recommended to include a link to the start of the body matter as well as to any major
reference sections (e.g., table of contents, endnotes, bibliography, glossary, index).
4.3.3.1 Helpful Resources
The following resources explain EPUB and ARIA landmarks in more detail.
[WCAG2] Success Criterion 2.4.2 requires
that each Web page include a title. EPUB has a similar requirement for EPUB Publications:
publications require a [DCTERMS] title element in the Package Document metadata.
The [WCAG2] requirement is not satisfied by the EPUB requirement, however.
When authoring an EPUB Publication each EPUB Content Document also requires a descriptive title
that describes its content. If not provided, Assistive Technologies often will announce the name
of the file to users.
If the title includes structural context (e.g., the part heading a chapter belongs to, or the
name of the publication), order the title such that the most precise description of the current
document comes first.
For more information about titles, see Technique H25.
To a user, an EPUB Publication appears as a single document that they read from beginning to end,
even though the content is often split across numerous EPUB Content Documents. As a result,
their natural expectation is that the headings reflect their position in the overall hierarchy
of the publication, despite the publication not actually being a single document (e.g., if a
part heading is expressed in an [HTML] h1 element, each chapter that belongs to
the part will have an h2 heading).
Technique G141: Organizing a page
using headings instructs EPUB Creators on correctly using numbered headings within a
document, but with EPUB Publications the numbered headings also need to remain consistent across
documents. Practically, this means that each EPUB Content Document does not have to begin with
an h1 heading unless the first heading is a top-level heading — the first heading
needs to have a numbered heading element that reflects its actual position in the
publication.
EPUB Creators also to need chunk their content so that the first heading in a document always has
the highest number. For example, if a document starts with an h3 heading, there
should not be an h2 heading later in the document (e.g., do not include the start
of a new section with the trailing subsections of the previous). It is acceptable for there to
be subsequent headings at the same level as the first (e.g., multiple subsections in one
document could all have h3 headings).
4.4.3 Heading topic or purpose
[WCAG2] Success Criterion 2.4.6
currently states that all headings must describe their topic or purpose. The implication of this
wording is that all chapters in a novel, for example, have a topic or purpose and that the topic
or purpose is always clearly reflected by the title of the chapter. Not only is this not always
the case, but this success criterion also complicates the use of chapter numbers as headings
since these do not establish a topic.
By this interpretation, the headings in publications should always pass provided they are
unique.
It is expected that the wording of the success criterion will be updated to better reflect the
uniqueness requirement, likely in the future WCAG 3 due the complexities of changing the wording
for WCAG 2.
4.5 Descriptions
4.5.1 Include alternative text descriptions
The first version of these techniques only required alternative text for images regardless of
their complexity. This exception is no longer valid.
EPUB Creators must now ensure that their image-based content meets [WCAG2] requirements for
alternative text and extended descriptions to conform with [EPUB-A11Y-11].
4.5.1.1 Helpful Resources
The following documents provide guidance on including extended descriptions:
[WCAG2] Success Criterions 3.1.1
and 3.1.2 deal with the language of
a page and changes of language with in, respectively.
For EPUB Publications, the Package Document is also an important source of metadata information
about the publication. For example, Reading Systems expose details of the publications to users
in their bookshelves using this information.
Consequently, it is necessary to provide the language of all text content in the Package Document
to conform with these WCAG success criteria. The easiest way to meet this requirement is to add
an xml:lang attribute on the root package element
[EPUB-3].
If individual metadata fields within the Package Document are expressed in a different language,
it is similarly required that the language change be identified by an xml:lang
attribute on the element for the field.
Providing this information enables Reading Systems to correctly render the text content in the
proper language for users.
Note
The languages specified in the Package Document have no effect on individual EPUB
Content Documents (i.e., the language of each document must be specified using the language
expression mechanisms it provides).
4.6.2 Language of the EPUB Publication
In addition to being able to express the language of text content, the Package Document also
allows EPUB Creators to identify the languages of the EPUB Publication in dc:language elements
[EPUB-3].
Although it is not strictly required to set this information to meet [WCAG2] Success Criterion 3.1.1, as it is
only informative, it should be considered a best practice to always set this field with the
proper language information. (Note that EPUB3 requires the language always be specified, so
omitting will fail validation requirements.)
Although Reading Systems do not use this language information to render the text content of the
EPUB Publication, they do use it to optimize the reading experience for users (e.g., to preload
text-to-speech engines so users do not have a delay when synthesizing the text).
Note
The languages specified in the Package Document have no effect on individual EPUB
Content Documents (i.e., the language of each document must be specified using the language
expression mechanisms it provides).
4.7 Text
4.7.1 Use Unicode for text content
[WCAG2] Success Criterion 1.1.1
requires that text equivalents be provided for all non-text content to meet Level A. In some
regions (e.g., Asia), it is not uncommon to find images of individual text characters, despite
the availability of Unicode character equivalents. This practice occurs for various reasons,
such as ease of translation of older documents and for compatibility across Reading Systems. The
use of images in most instances leads to the text not being accessible to non-visual users,
however.
When individual characters are replaced by images, there is invariably a negative effect on
text-to-speech playback, even when alternative text is provided (e.g., if single characters
within a word are replaced by images, the word will not be read as a single unit of text). It is
also problematic for visual users, as the images often scale poorly and the characters cannot be
changed to different font families to meet user preferences.
The use of Unicode characters for all text content avoids this problem, allowing content to
successfully meet the minimum requirement for Level A.
For compliance with Level AA, EPUB Creators are directed to Success Criterion 1.4.5 which further
restricts the use of images of text to only a set of essential cases.
4.8 Accessible Alternatives
As EPUB Publications can be composed of more than one rendition, it is possible that different
versions of the content will have different levels of accessibility. For example, an image-based
version of the content that lacks alternative text or descriptions could be bundled with a
WCAG-compliant text-based serialization. This type of accessible bundling is acceptable, as
[WCAG2] allows non-conforming content provided a conforming alternate
version is available.
The [EPUBMultipleRenditions-10] specification defines a set of features for creating these types of
EPUB Publications. It specifies a set of attributes that allow a Reading System to automatically
select a preferred rendition for the user or to provide the user the option to manually select
between the available options. This functionality technically meets the requirements of [WCAG2] in
terms of ensuring the user can access the accessible version.
In practice, however, the [EPUBMultipleRenditions-10] specification is not broadly supported in
Reading Systems at the time of publication. As a result, a user who obtains an EPUB Publication that
contains more than one rendition will only have access to the default. Unless this rendition is the
accessible one, the EPUB Publication might not be readable by them.
EPUB Creators therefore need to use their best discretion when implementing this functionality to
meet accessibility requirements. EPUB Publications that contain multiple renditions are conformant
to the [EPUB-A11Y-11] specification if at least one rendition meets all the content requirements,
but EPUB Creators at a minimum need to note that a Reading System that supports multiple renditions
is required in their accessibility summary. Any other methods the EPUB
Creator can use to make this dependence known is advisable (e.g., in the distribution metadata).
This section will be updated with techniques for using multiple renditions when there is enough
support in Reading Systems to broadly recommend their use.
5. EPUB Techniques
5.1 Page Markers
5.1.1 Provide page break markers
Both the EPUB Structural Semantics Vocabulary [EPUB-SSV] and Digital Publishing WAI-ARIA 1.0
Module [DPUB-ARIA-1.0] include a semantic for static page breaks: pagebreak and doc-pagebreak,
respectively.
It is recommended that both semantics be applied to EPUB 3 content to ensure maximum
compatibility with Reading Systems and Assistive Technologies.
A title or aria-label attribute is required on the element, as it
provides the value that is announced to the user. Do not include the page number as text
content, as this practice forces the user to hear it announced wherever it occurs (e.g., without
any context in the middle of a sentence).
EPUB 2 does not include markup to identify static page break marks in the content. Page break
destinations can be included to enable hyperlinking, but the page
list is the only way a user can jump to the locations.
Do not use the [HTML] a element to identify page break locations in EPUB 3 Publications.
Although this element was previously defined as the anchor for a hyperlink destination, its
purpose has been changed in [HTML] for use solely as a link.
5.1.2 Identify pages in audio playback
Readers rarely stop reading to review each new page number, so when page numbers are read aloud
in the audio playback of a publication it is not only distracting, but can be confusing, as well
(e.g., the number could be read out in the middle of a sentence).
To mitigate this potential annoyance to readers, EPUB Creators need to identify page
announcements in the EPUB 3 media overlays document when they are included. Identification
allows a Reading System to provide a playback experience where the numbers are automatically
skipped.
To identify page numbers in EPUB 3 Publications, attach an epub:type attribute with
the value "pagebreak"
[EPUB-SSV] to each par
element [EPUB-3] that identifies a page number in the media overlay documents.
Note that as EPUB 2 does not provide text and audio synchronization, this technique does not
apply.
5.1.3 Provide a page list
A page list — a list of hyperlinks to the static page break locations — is the most effective way
for users to find static page locations. Without a page list, the user would have to navigate
each page marker in the text, provided they are available and the Reading System provides such
functionality.
When a page list is included, Reading Systems can provide users direct access to the list or use
it to provide automatic page jump functionality.
The EPUB Navigation Document allows the inclusion of a page-listnav [EPUB-3], while the EPUB 2 NCX file provides the same functionality
through the pageList element [OPF-201].
5.1.4 Identify the pagination source
Users typically want to know the source of the page break markers included in an EPUB Publication
when they are derived from a static media. Considerations like which printing, by which
publisher or imprint, and whether the pagination comes from the hard or soft cover edition will
affect decisions about its usefulness (e.g., does it exactly match the pagination of a print
book used in a classroom).
To allow users to determine the suitability of the pagination, identify the ISBN of the source
work in the Package Document metadata.
EPUB 3 allows the source of pagination to be explicitly identified using the source-of property with the
value "pagination" [EPUB-3].
The source-of property is particularly useful when there are multiple sources for an
EPUB Publication as it disambiguates which one the pagination came from.
If an ISBN is not available, include as much information as possible about the source publication
(e.g., the publisher, date, edition, and binding).
If the page break markers are unique to the EPUB Publication, do not identify a print source.
6. Distribution Techniques
6.1 Do not restrict access through digital rights management
EPUB Publications typically require preservation of the publisher's and author's intellectual
property when distributed (e.g., so that they can be made available for individual sale through
online bookstores or distributed through library systems). The most common way to address this need
has been through the application of digital rights management (DRM) schemes to the packaged EPUB
Publication. DRM enables a variety of security features that aren't native to the EPUB format, such
as the ability to limit access to a single user and to limit the length of time the person can
access the publication (e.g., library loans).
In general, DRM can be made to work interoperably with Assistive Technologies, but problems arise
when DRM restrictions remove direct access to an EPUB Publication or restrict access to the content
within it. Unless the Reading System implementing the DRM provides API level access to the content,
it can prove difficult, or even impossible, to generate text-to-speech playback, or for a
refreshable braille display to have access to the underlying text, as well as cause other
accessibility issues.
The application of digital rights management therefore must not impair or impede the functionality of
Assistive Technologies on EPUB Publications users have the right to access.
6.2 Include accessibility metadata in distribution records
When an EPUB Publication is ingested into a distribution system, such as a bookstore or library, a
metadata record is often provided separately to the distributor. In these scenarios, the metadata
used to enable discovery of the publication typically comes from the distribution record alone, not
from the metadata in the Package Document.
The result is that it is necessary to include as much accessibility metadata in distribution records
as their vocabularies allow.
Note
The use of distribution records does not remove the requirement to include accessibility metadata
in the Package Document. The metadata in the Package Document ensures accessibility information
is always available with the publication.
6.2.1 Helpful Resources
See the following resources for more information about including accessibility metadata in
distribution records:
Note that this change log only identifies substantive changes since EPUB Accessibility Techniques 1.0 — those
that affect the conformance of EPUB Publications or are similarly noteworthy.
10-Nov-2021: Added techniques for setting language in the Package Document. See issue 1842.
25-Oct-2021: Removed the generic technique labels for each section. See issue 1866.
29-Sep-2021: Added TITLES-003 to explain that headings only have to be
unique, not define the topic or purpose of a section. See issue 1810.
10-June-2021: Clarified the technique on meaningful sequence that it applies to content that spans
pages in a spread and is not about ordering documents in the spine. See issue 1695.
25-May-2021: Updated the section on ARIA roles to make clear that the epub:type
attribute does not have to be used in coordination, nor that roles are required where
epub:type is used.
13-Apr-2021: Added an example of using the source-of property in EPUB 3 to identify
which dc:source element is the source of pagination. See issue 1600.
19-Feb-2021: References to WCAG 2.0 have been updated to undated references to WCAG 2 (except where
WCAG 2.0 is explicitly mentioned for conformance).
16-Nov-2020: The techniques for accessibility controls and APIs have been replaced with descriptions of why these properties are not
necessary to set. See issue 1286.
B. Acknowledgements
This section is non-normative.
The following members of the EPUB 3 Working Group contributed to the development of this specification:
Juliette Alexandria (Access2online Inc.)
Luc Audrain (W3C Invited Expert)
Will AWAD (Newgen Knowledgeworks)
Sofia Bautista (Legible Media Inc.)
Laura Brady (W3C Invited Expert)
Leah Brochu (National Network for Equitable Library Service)
Matthew C. Chan (House of Anansi Press)
Yu-Wei Chang (Taiwan Digital Publishing Forum)
Fred Chasen (Scribd)
Garth Conboy (Google LLC)
Juan Corona (Legible Media Inc.)
Dave Cramer (W3C Invited Expert, chair)
Romain Deltour (DAISY Consortium)
Marisa DeMeglio (DAISY Consortium)
Brady Duga (Google LLC)
Reinaldo Ferraz (NIC.br - Brazilian Network Information Center)
John Foliot (W3C Invited Expert)
Teenya Franklin (Pearson plc)
Hadrien Gardeur (EDRLab)
Matt Garrish (DAISY Consortium)
Jen Goulden (Crawford Technologies)
Ivan Herman (W3C, staff contact)
Tetsu Hoshino (Kodansha, Publishers, Ltd.)
Norikazu Ishizu (Kadokawa Corporation)
Norihito IYENAGA (Kodansha, Publishers, Ltd.)
Ken Jones (Circular Software)
Deborah Kaplan (W3C Invited Expert)
Bill Kasdorf (Book Industry Study Group)
George Kerscher (DAISY Consortium)
Kazuhito Kidachi (Mitsue-Links Co., Ltd.)
Masakazu Kitahara (Voyager Japan, Inc.)
Toshiaki Koike (Voyager Japan, Inc.)
Ryo Kuroda (ACCESS CO., LTD.)
Charles LaPierre (Benetech)
Dan Lazin (Google LLC)
Laurent Le Meur (EDRLab)
Farrah Little (National Network for Equitable Library Service)
Karan Malhotra (Newgen Knowledgeworks)
Makoto Murata (DAISY Consortium)
Cristina Mussinelli (Fondazione LIA)
Yoichiro Nagao (Kodansha, Publishers, Ltd.)
Yoshinori Ohmura (SHUEISHA Inc.)
Rachel Osolen (National Network for Equitable Library Service)