This specification specifies content conformance requirements for verifying the accessibility of EPUB®
Publications. It also specifies accessibility metadata requirements for the discoverability of EPUB
Publications.
Status of This Document
This section describes the status of this
document at the time of its publication. Other documents may supersede
this document. A list of current W3C publications and the latest revision
of this technical report can be found in the
W3C technical reports index at
https://www.w3.org/TR/.
Editor's note
Publishers not currently producing accessible content are encouraged to begin updating their
production processes to meet the requirements of [EPUB-A11Y-10] while this specification is being
developed. Content that meets the requirements of that version will typically also meet the
requirements of this specification with few changes necessary.
This document was published by the EPUB 3 Working Group as a
Working Draft.
This document is intended to become a W3C Recommendation.
Publication as a Working 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. It is inappropriate to cite this
document as other than work in progress.
This document was produced by a group
operating under the
W3C Patent
Policy.
W3C maintains a
public list of any patent disclosures
made in connection with the deliverables of
the group; that page also includes
instructions for disclosing a patent. An individual who has actual
knowledge of a patent which the individual believes contains
Essential Claim(s)
must disclose the information in accordance with
section 6 of the W3C Patent Policy.
This specification, EPUB Accessibility, addresses two key needs in the EPUB ecosystem:
discoverability of the accessible qualities of EPUB Publications; and
evaluation and certification of accessible EPUB Publications.
The provision of accessibility metadata facilitates informed decisions about the usability of an EPUB
Publication. Consumers can review the qualities of the content and decide whether an EPUB
Publication is appropriate for their needs, regardless of whether it meets the bar of accessible
certification. At a minimum, all EPUB Publications that conform to this specification meet the
accessibility metadata requirements described in § 2. Discoverability.
Although EPUB Creators have always been able to create EPUB Publications with a high degree of
accessibility, this specification sets formal requirements for certifying content accessible. These
requirements provide EPUB Creators a clear set of guidelines to evaluate their content against and
allows certification of quality. An accessible EPUB Publication is one that meets the accessibility
requirements described in § 3. Accessible Publications.
The specification also discusses the practice of optimizing EPUB Publications for specific reading
modalities. In these cases, the content cannot meet the broad accessibility requirements of this
specification, but by following its discoverability and reporting requirements EPUB Creators can
improve the ability of users to determine if the content still meets their needs. Refer to § 4. Optimized Publications for more information.
The specification also addresses the impact of distribution on the accessibility and discoverability
of content in § 5. Distribution.
This specification does not target a single version of EPUB. It is applicable to EPUB Publications
that conform to any version or profile, including future versions of the standard.
Ideally, these guidelines help evaluate any digital publication built on Open Web technologies,
although ensuring such application is outside the scope of this specification.
This specification takes an abstract approach to the accessibility requirements for EPUB
Publications, similar to how WCAG [WCAG2] separates its accessibility guidelines from the
techniques to achieve them. This approach allows the guidelines to remain stable even as the format
evolves.
To facilitate this approach, the companion EPUB
Accessibility Techniques [EPUB-A11Y-TECH-11] document outlines conformance techniques.
These techniques explain how to meet the requirements of this specification for different versions
of EPUB.
This specification is also designed to address the accessibility needs of users independent of
what languages they read. The same is true for the principles and success criteria defined in
[WCAG2]. The goal is to ensure that users can fully consume the information of a publication
regardless of their preferred reading modality.
At the same time, the language and writing conventions of the authored text will influence the
techniques necessary to meet the accessibility requirements. EPUB requires support for Unicode text
[EPUB-3], for example, which ensures the correct character data can be used (i.e., EPUB
Creators do not have to use images of text). Although this is an important feature, it is often
not enough on its own to ensure that the text is fully accessible in any given language (e.g.,
additional information about directionality, emphasis, pronunciation, etc. may also be
needed).
As a consequence, there may be language- or culture-specific practices for meeting accessibility
requirements. Whether these practices are defined within this specification and its techniques
or elsewhere (e.g., in WCAG techniques or language-specific best practice recommendations) will
depend on whether the issues are specific to EPUB or broadly affect all Web content.
1.3 Application to Older Versions
This section is non-normative.
This specification is applicable to any EPUB Publication, even if the content conforms to an older
version of EPUB that does not refer to this specification (e.g., EPUB 2 [OPF-201]).
Creators of such EPUB Publications should create content in conformance with the accessibility and
discoverability requirements of this specification. EPUB Creators should also upgrade to the latest
version of EPUB to get access to the most advanced accessibility features and techniques.
1.4 Terminology
This specification 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.
1.5 Conformance
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The key words MAY, MUST, MUST NOT, OPTIONAL, RECOMMENDED, and SHOULD in this document
are to be interpreted as described in
BCP 14
[RFC2119] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
2. Discoverability
2.1 Introduction
This section is non-normative.
Unlike web pages, EPUB Creators distribute EPUB Publications through many channels for personal
consumption — a model that has made EPUB a successful format for ebooks and other types of digital
publications. A consequence of this model, however, is that specific details about the accessibility
of a publication must travel with it.
An online bookstore aggregating content from publishers and authors, for example, does not know the
production quality that went into each submission unless the publisher informs them through
metadata.
Ensuring that any interested party can discover the accessible qualities of an EPUB Publication is
therefore a primary concern. Users must be able to gauge the usability of an EPUB Publication when
they purchase, borrow, or otherwise obtain it, a determination that requires knowing the affordances
made to meet the accessibility requirements.
Similarly, content that does not meet the accessibility requirements of this specification does not
necessarily fail to meet the needs of individual users.
Only through the provision of rich metadata can a user decide if the content is suitable for
them.
2.2 Package Metadata
All EPUB Publications MUST include [schema-org] accessibility metadata in the Package Document that
exposes their accessible properties, regardless of whether the publications also meet the accessibility or optimization
requirements.
EPUB Publications MUST include the following accessibility metadata:
accessMode — a
human sensory perceptual system or cognitive faculty necessary to process or perceive the
content (e.g., textual, visual, auditory, tactile).
accessibilityFeature — features and adaptations that contribute to the overall
accessibility of the content (e.g., alternative text, extended descriptions, captions).
accessibilityHazard — any potential hazards that the content presents (e.g.,
flashing, motion simulation, sound).
accessibilitySummary — a human-readable summary of the overall accessibility, which
includes a description of any known deficiencies (e.g., lack of extended descriptions,
specific hazards).
EPUB Publications SHOULD include the following [schema-org] accessibility metadata:
accessModeSufficient — a set of one or more access modes sufficient to consume the
content without significant loss of information. An EPUB Publication can have more than one
set of sufficient access modes for its consumption depending on the types of content it
includes (i.e., unlike access modes, this property
takes into account any affordances for content that is not broadly accessible, such as the
inclusion of transcripts for audio content).
EPUB Creators MAY include additional [schema-org] accessibility metadata not specified in this
section.
Accessibility metadata can also be included in linked records [EPUB-3] (i.e., metadata records referenced from link
elements), but the inclusion of such metadata solely in a linked record does not satisfy the
discoverability requirements of this specification.
3. Accessible Publications
3.1 Introduction
This section is non-normative.
EPUB builds on the Open Web Platform, with HTML, CSS, JavaScript and SVG, the core technologies used
for content authoring. The use of these technologies means that EPUB Creators can author EPUB
Publications with a high degree of accessibility simply through the proper application of
established web accessibility techniques.
The primary source producing accessible web content is the W3C Web Content Accessibility Guidelines
(WCAG) [WCAG2]. This specification leverages the extensive work done in WCAG to establish
benchmarks for accessible content, and the same four high-level content principles — perceivable,
operable, understandable, and robust — are central to creating EPUB Publications that are
accessible.
This section defines how to apply the conformance criteria defined in WCAG and addresses qualities
unique to EPUB Publications.
EPUB Publications authored to comply with the requirements in this section will have a high degree of
accessibility for users with a wide variety of reading needs and preferences.
3.2 Relationship to WCAG
This section is non-normative.
WCAG [WCAG2] and its associated techniques
provide extensive coverage of issues and solutions for web content accessibility — from tables to
embedded multimedia to rich semantics. They represent the foundation that this specification builds
upon.
This specification does not repeat the requirements or techniques introduced in those documents, as
it risks breaking compatibility between the two standards (e.g., putting guidance out of sync, or in
conflict). At the same time, although this specification does not call out those requirements, it
does not diminish their importance in creating EPUB Publications that are accessible.
This specification instead defines how to apply WCAG to an EPUB Publication — which is a collection of web documents as opposed to a single page — and
adds an additional set of requirements. These requirements are no more
or less important than those covered in WCAG; they are simply necessary to follow for EPUB
Publications. (Each requirement explains its relationship to WCAG in its respective section.)
The same is true of the techniques in the EPUB Accessibility Techniques document
[EPUB-A11Y-TECH-11]. It provides coverage of techniques that are unique to EPUB Publications, or
that need clarification in the context of an EPUB Publication. It does not mean that the rest of the
WCAG techniques are not applicable.
As a result, although EPUB Creators can read this section without deep knowledge of WCAG conformance,
to implement the accessibility requirements of this specification requires an understanding of
WCAG.
Because this specification adds requirements that are not a part of WCAG, an EPUB Publication can
conform to WCAG without conforming to this specification.
3.3 WCAG Conformance
3.3.1 WCAG Conformance Requirements
To conform to this specification, an EPUB Publication:
MUST meet the requirements of Level A, but it is strongly RECOMMENDED
that it meet the requirements of Level AA
[WCAG2].
The reporting flexibility offered by these requirements is to ensure that this specification can
be adapted for use in regions that mandate accessibility but without negating or superseding the
requirements in effect in those regions.
This specification sets the baseline requirement to WCAG 2.0 Level A, for example, primarily to
provide EPUB Creators backwards compatibility for older content and flexibility to encourage
adoption of accessible production where no formal requirements exist. Most accessibility
practitioners do not recognize this level as providing a high degree of accessibility,
however.
Ideally, EPUB Creators should try to conform to the latest version of WCAG 2 at Level AA, but
local and national laws, or procurer or distributor requirements, will define the formal
thresholds they must meet.
Note
Examples of legislative requirements for accessibility include the Directive
2019/882 in the European Union and Section 508 of the Rehabilitation Act of 1973 in the United States. EPUB
Publications will need to meet more than just the basic Level A success criteria to be
compliant with these laws.
Keeping pace with WCAG has the benefit of continuously enhancing access for users. As web
technologies change and improve, and awareness of conditions that impede access evolve, the
standard adds new requirements. Meeting these additional requirements helps ensure EPUB
Publications employ the most up-to-date techniques. Meeting the requirements of older versions,
while still helpful, can result in a less optimal reading experience.
Similarly, legal frameworks and policies often cite Level AA conformance as the benchmark for
accessibility. The reason is that it provides the greatest range of improvements that EPUB
Creators can realistically implement (EPUB Creators should try to meet the AAA requirements if
they can, but fully conforming at AAA is typically not possible). When EPUB Creators meet only
Level A conformance, they compromise their content for various user groups, resulting in a less
optimal reading experience.
Note
The W3C Accessibility Guidelines Working Group is
currently developing WCAG 3. As this version potentially represents a significant departure
from WCAG 2, a future version of this specification will address conformance requirements
related to it. EPUB Creators are encouraged to adopt WCAG 3 once it is stable and widely
recognized, but conformance to the new version is not a requirement of this standard.
3.3.2 Evaluating WCAG Conformance
3.3.2.1 Page and Publication
The WCAG principles
[WCAG2] focus on the evaluation of individual web pages, but an EPUB Publication more
closely resembles what WCAG refers to as a set of web pages: "[a]
collection of Web pages that share a common purpose" [WCAG2].
Consequently, when evaluating the accessibility of an EPUB Publication, EPUB Creators cannot
review individual pages — or Content Documents, as they are known in EPUB 3 — in isolation.
Rather, EPUB Creators MUST evaluate their accessibility as part of the larger work.
For example, it is not sufficient for EPUB Creators to give individual EPUB Content Documents
a logical reading order if they list the documents in the wrong reading order. Likewise,
including a title for every EPUB Content Document is complementary to providing a title for
the publication: the overall accessibility decreases if either is missing.
EPUB Creators MUST evaluate the WCAG guidelines for content to be perceivable, operable,
understandable, and robust against the full EPUB Publication, not only against each Content
Document within it.
The EPUB Accessibility Techniques [EPUB-A11Y-TECH-11] provide more information about
applying these guidelines to EPUB Publications.
When determining compliance with a conformance level, the whole EPUB Publication MUST
meet the conformance requirements of the level claimed.
EPUB Creators MUST NOT use EPUB's fallback mechanisms to provide a conforming
alternate version [WCAG2], as there is no reliable way for users to access
such fallbacks. If an EPUB Creator uses fallbacks, both the primary content and its
fallback(s) MUST meet the requirements for the conformance level claimed. EPUB-specific
fallback mechanisms include manifest
fallbacks [EPUB-3], bindings [EPUB-3] and content switching via the epub:switch
element [EPUB-3].
When determining compliance with the "Full
Pages" requirement [WCAG2] (i.e., that parts of a page cannot be excluded when
making a conformance claim), the entirety of each EPUB Content Document MUST achieve the
conformance level and every Content Document in the EPUB Publication MUST meet
the stated conformance level.
3.4 EPUB Requirements
3.4.1 Page Navigation
3.4.1.1 Overview
This section is non-normative.
Statically paginated content is still ubiquitous, as print continues to be the most consumed
medium for books both among the general reading public and in educational settings. Print is
not the only source of static pagination, either: static page boundaries are also present in
fixed-layout digital publications.
As a result, non-visual readers face disadvantages relative to their peers in environments
that use statically paginated content as they cannot easily locate the same locations in a
publication (e.g., if a teacher instructs students to all turn to a specific page).
The inclusion of page boundary locations helps bridge this disparity by ensuring the choice
of reflowable media does not disadvantage those users.
Providing page navigation also helps in reflowable publications that do not have a statically
paginated equivalent. The default pagination of these publications by Reading Systems is not
static since it changes depending on the viewport size and user's font settings. As a
result, coordinating locations among users of the same EPUB Publication can be complicated
without static references.
The inclusion of page navigation represents one method of achieving the Multiple Ways success criterion
[WCAG2], as it provides another meaningful way for users to access the content (e.g., in
addition to the table of contents, linear reading order and any other navigation aids).
Given the importance of page navigation in mixed print/digital environments, the requirement
to include this feature has higher precedence than it would solely as one of many ways to
meet the Multiple Ways success criterion.
An EPUB Publication SHOULD meet the page navigation objectives defined in this section
whenever any of the following cases is true:
the EPUB Creator identifies the EPUB Publication as the dynamically paginated equivalent
of a statically paginated publication (e.g., included in a print/digital bundle);
the EPUB Creator offers the EPUB Publication as an alternative to a statically paginated
publication in an environment where they can reasonably predict the use of both versions
(e.g., educational settings); or
the EPUB Creator generates the EPUB Publication and a statically paginated publication
from a workflow that allows the retention of page break locations across formats.
EPUB Creators MAY include page navigation in reflowable EPUB Publications without statically
paginated equivalents.
3.4.1.3 Objectives
3.4.1.3.1 Pagination Source
Objective
Identify the source of static page break locations.
Understanding this Objective
Users need to know the source of the pagination in an EPUB Publication to
determine whether it will be useful for their needs. Print publications, for
example, produced in both hard and soft cover editions will have different
pagination. Different editions of the same book often also have different
pagination.
Including a recognizable identifier for the statically paginated source, such as
its ISBN or ISSN, ensures that users can determine which version the pagination
corresponds to.
If EPUB Creators insert pagination as a navigation aid for digital-only
publications, they must not specify a source (i.e., do not identify the current
publication as the source of its own pagination).
Meeting this Objective
When an EPUB Publication includes page break
markers and/or a page list that correspond
to a statically-paginated version of the publication, EPUB Creators MUST
identify that source in the Package Document metadata.
3.4.1.3.2 Page List
Objective
Provide navigation to static page break locations.
Understanding this Objective
The page list is the primary means of navigating to page break locations as it
provides a list of links to each of the static page break locations in the EPUB
Publication.
Reading Systems typically use this list to generate a "go to page" interface in
which users can plug in the page number that they wish to move to, but sometimes
offer users the ability to access the full list and select the page number to go
to.
Without a page list, page navigation becomes extremely difficult as it would rely
on navigating the individual page break markers
(if they are even present).
Meeting this Objective
An EPUB Publication MUST include a page list.
EPUB Creators SHOULD include links to all pages of content reproduced from the
source (i.e., they do not have to provide links for blank pages or content not
reproduced in the digital edition).
EPUB Creators should include links for all pages in the source whether they are
reproduced or not, but this is not a requirement.
3.4.1.3.3 Page Breaks
Objective
Provide static page break locations.
Understanding this Objective
Inserting page break markers into an EPUB Publication provides users with context
about where they are in the text. Assistive technologies can use this
information to announce the current page number the user is on, for example, if
the user wants to cite something on the page.
The inclusion of page break markers can also allow users to move quickly forwards
and backwards by page without having to access the page list each time.
The inclusion of these markers also simplifies the creation of a page list, as they provide easily referenced
destinations for the links.
Meeting this Objective
Inclusion of page break markers in an EPUB Publication is OPTIONAL.
If an EPUB Creator includes page break markers:
they SHOULD include page break markers for all pages reproduced from the
source (i.e., blank pages and content not reproduced in the digital edition
do not require markers).
they should include page break markers for all pages in the source (whether
reproduced or not), but this is not a requirement.
In addition, if page numbers are read aloud in a synchronized text-audio playback
of the content (e.g., EPUB 3 Media Overlays [EPUB-3]), EPUB Creators MUST
identify the page numbers in the markup that controls the playback.
3.4.2 Media Overlays Playback
3.4.2.1 Overview
This section is non-normative.
Media Overlays provide an accessible playback experience for anyone who benefits from having
text and audio synchronized. They are also useful to users who only require audio playback,
or only benefit from reading with text highlighting. Media Overlays also enable a seamless
playback experience from beginning to end of an EPUB Publication for all these users.
The most basic Media Overlay
Documents [EPUB-3] provide only minimal instructions to Reading Systems, however.
They indicate the text to highlight and the audio clip that corresponds to the text. The
result is that users only have basic start and stop options available.
EPUB Creators need to add structure and semantics to Media Overlay Documents to allow Reading
Systems to present more usable experiences. With richer markup, a Reading System could
provide the ability to skip past secondary content that interferes with the primary
narrative, escape users from deeply nested structures like tables, and allow them to
navigate through the sections of the publication without having to go to the table of
contents.
Adding structure and semantics to Media Overlay Documents broadly falls under the objective
of the Info and Relationships
success criterion [WCAG2]. Without structured and semantically meaningful playback
sequences, the effect is to deprive users of rich navigation of the content.
3.4.2.2 Applicability
Media Overlay Documents MUST meet the requirements in [EPUB-3]. It is not necessary to meet
any additional requirements beyond those defined in [EPUB-3] to be conformant with this
specification.
To maximize the effectiveness of Media Overlays for people with different reading needs,
however, EPUB Creators are strongly encouraged to meet the OPTIONAL
objectives defined in the next section.
Note
EPUB Creators do not have to include Media Overlays in their EPUB Publications, only
ensure they conform to these requirements when present.
3.4.2.3 Objectives
3.4.2.3.1 Completeness
Objective
Ensure that the full text is available in audio.
Understanding this Objective
Although it is possible for users who require a publication in audio form to use
text-to-speech playback, the experience is considerably poorer than when
pre-recorded narration is provided. Text-to-speech engines have limited built-in
vocabularies, causing them to mangle and mispronounce most uncommon words they
encounter. As a result users have to have words repeated and spelled out to make
sense of the content, slowing down their reading and reducing comprehension.
For this reason, it is important to provide narration for the full text of a
publication in addition to the full text. Users can then decide which reading
modality they prefer — text, audio, or a mix of the two.
Meeting this Objective
EPUB Creators MUST provide synchronized audio playback via Media Overlays for all
textual content.
3.4.2.3.2 Reading Order
Objective
Ensure Media Overlay playback matches logical reading order.
Understanding this Objective
Every EPUB Publication has a default reading order that allows users to logically
progress through the content. It ensures that readers can follow the primary
narrative and that they encounter secondary content where it makes the most
sense. The default reading order also establishes some less obvious relations,
like the progress within a table from cell to cell and row to row.
If the sequence of par and seq elements in a Media
Overlay Documents does not match this progression, it can cause confusion for
readers, whether they are only listening to the audio or trying to also follow
visually.
Ordering the playback to match the default reading order is the safest way to
ensure that users can follow the text. In some cases, however, strict adherence
to this practice could result in a suboptimal reading experience (e.g., playback
of a table by column instead of row might make more logical sense in some
cases). The goal of this objective is not to forbid alternate presentations, but
to ensure that any deviations retain the logical flow of the content.
Meeting this Objective
EPUB Creators SHOULD order the par and seq elements in
a Media Overlays Document such that they reflect both:
the order of the referenced EPUB Content Documents in the spine [EPUB-3];
and
the order of each element within its respective EPUB Content Document.
If EPUB Creators use a different ordering, that ordering MUST still result in a
logical playback of the content.
3.4.2.3.3 Skippability
Objective
Enable users to automatically skip over content.
Understanding this Objective
Being able to read the primary narrative of a work without interruption is
central to reading comprehension. EPUB Creators typically structure EPUB
Publications to visually represent secondary information such as sidebars and
footnotes outside the main narrative flow (e.g., by using different background
colours or placement so readers can filter this information visually out while
reading).
Readers who prefer auditory playback, however, cannot skip this information with
the same ease by default. Media overlays playback will typically result in
Reading Systems rendering secondary content where it occurs.
When EPUB Creators add structural semantics to Media Overlay Documents, however,
Reading Systems can create reading experiences that allow users to decide which
secondary content to skip by default during playback.
Enable users to automatically escape from structured content.
Understanding this Objective
When reading visually, users can quickly move through, and escape from, highly
structured content such as tables, lists, and figures. Table layouts that use
rows and columns, for example, allow users to quickly move along either axis to
find the information they want, and to easily return to the primary narrative
when they finish. Similarly, lists of items allow users to skim their content
and escape from them once they locate the desired information.
The same ease of escaping from content is not available in Media Overlay
Documents by default. Users cannot escape from table cells, rows, or even the
table itself, unless EPUB Creators encode the structural semantics of those
elements in the document.
When EPUB Creators provide this information, Reading Systems can simplify
playback for auditory readers to enable a comparable reading experience.
Ensure auditory playback is possible for the navigation aids in the EPUB
Navigation Document when presented by Reading Systems.
Understanding this Objective
Reading Systems typically provide their own interfaces to the navigation aids in
the EPUB Navigation Document. For example, they open the table of contents as a
specialized interface on top of the content the user is reading.
To access these interfaces, users typically must rely on text-to-speech playback,
when available, to hear the entries.
Providing a Media Overlay Document for the EPUB Navigation Document provides
Reading Systems the ability to use auditory labels for the links, improving the
experience for auditory readers.
The metadata uses a combination of properties from DCMI Metadata Terms [DCTERMS] and the EPUB Accessibility Vocabulary, as explained in more detail in the
following sections.
3.5.2 Publication Conformance
To indicate that an EPUB Publication conforms to the accessibility requirements of this
specification, it MUST include a conformsTo property whose value MUST exactly match
(i.e., both in case and spacing) the following pattern:
EPUB Creators MUST specify the version number of the EPUB Accessibility specification the
publication conforms to, not including the decimal points. EPUB Creators MUST use the
value 11 to indicate this version of this specification.
WCAG-VER
EPUB Creators MUST specify the version number of WCAG the publication conforms to, not
including the decimal points (e.g., 20 for WCAG 2.0 or 21 for
WCAG 2.1).
WCAG-LVL
EPUB Creators MUST specify the WCAG conformance level the publication conforms to (e.g.,
A or AA).
The following conformance strings are valid as of publication of this specification:
EPUB-A11Y-11_WCAG-20-A
EPUB-A11Y-11_WCAG-20-AA
EPUB-A11Y-11_WCAG-20-AAA
EPUB-A11Y-11_WCAG-21-A
EPUB-A11Y-11_WCAG-21-AA
EPUB-A11Y-11_WCAG-21-AAA
Note
The list of valid conformance strings will increase as W3C releases new versions of WCAG.
Note
The future 3.0 version of WCAG is likely to
also introduce new level names (currently Bronze, Silver and Gold). Those names would
replace A, AA, and AAA in the string pattern.
Note
EPUB Creators may use a conformance URL, as defined in the Required Components of a
Conformance Claim [WCAG2], with the conformsTo property for EPUB
Publications that only meet WCAG conformance requirements (i.e., that do not fully conform
to this specification).
As [WCAG2] does not define how to specify the conformance level in the URL, however, EPUB
Creators will have to find an alternative means of relating this information when necessary
(e.g., through the accessibility summary).
3.5.3 Evaluator Information
EPUB Publications MUST include an a11y:certifiedBy
property that specifies the name of the party that evaluated the EPUB Publication.
Note
Any individual or party can perform a conformance evaluation. The evaluator can be the same
party that created the EPUB Publication or a third party.
Note
If an organization evaluates an EPUB Publication, users will typically want to know the name
of that organization. This specification discourages including the name of the individual(s)
who carried out the assessment, instead of the name of the organization, as this can
diminish the trust users have in the claim.
The date the evaluation was performed on MAY be specified by linking a dcterms:date property [DCTERMS] to the certifier.
If the party that evaluates the content has a credential or badge that establishes their
authority to evaluate content, include that information in an a11y:certifierCredential property.
If the party that evaluated the content provides a publicly-readable report of its assessment,
provide a link to the assessment in an a11y:certifierReport property.
Note
As each metadata format is unique in what it can express, this specification does not mandate
how to express conformance metadata outside of the EPUB Package Document.
Note
This specification does not define requirements for accessibility metadata external to an
EPUB 3 publication as part of distribution metadata. Ensuring consistency between internal
and external accessibility metadata expressions is the responsibility of authors,
publishers, and distributors. For further discussion of the effects of distribution on
accessibility, see § 5. Distribution.
3.5.4 Re-Evaluating Conformance
This section is non-normative.
Note
The following guidance is to help EPUB Creators determine when a new evaluation is necessary.
It is not a requirement to conform to this specification.
How long a conformance evaluation of an EPUB Publication is good for is a complex question.
Unlike web sites, which are continuously evolving, EPUB Creators may not update EPUB
Publications after their initial publication. As a result, an unmodified EPUB Publication will
always conform to its last evaluation.
It is common in publishing, however, to release updated versions of an EPUB Publication to fix
errors and typos in the work, as well as to periodically release new editions. As not all
changes to an EPUB Publication substantively change its accessibility, this complicates the
question of when EPUB Creators should perform a new evaluation, as well as whether a full or
partial re-evaluation will suffice.
As a rule, EPUB Creators must re-evaluate their content whenever they make substantive changes to
the structure and functionality of an EPUB Publication, such as:
modifications to the nature or order of markup in EPUB Content Documents;
additions or modifications to images that convey information;
modifications to formatting that affects the readability (e.g., contrast); and
additions or modifications to interactive controls, forms, etc.
If the EPUB Publication includes substantively the same markup and content as the previous
release, the EPUB Creator may only need to evaluate the new modifications to re-confirm
conformance.
If an updated version of this specification or [WCAG] has been published since the last release
of the EPUB Publication, however, this specification also recommends performing a new evaluation
to ensure conformance to the latest standards. EPUB Creators may not have to perform a full
re-evaluation even in this case (i.e., they may only need to check new or modified success
criteria unless the standards undergo major changes to methodology or conformance).
Conversely, EPUB Creators do not need to perform a re-evaluation when making non-substantive
changes, such as:
fixes for typographic errors in the text (i.e., no markup is changed);
additions or modifications to decorative images;
modifications to the formatting that do not affect the understanding of the content or
change the text display; and
modifications to Package Document metadata.
Individuals qualified to assess the accessibility of EPUB Publications should make the
determination of whether changes are substantive or not. An editor, for example, may not realize
the impact of seemingly minor formatting changes.
Even in the case of non-substantive changes, this specification recommends an updated evaluation
(full or partial) if the accessibility standards have changed.
EPUB Creators should consider even more progressive approaches than those described here. Waiting
for content changes before reviewing and updating the accessibility of EPUB Publications can
leave them lacking recent improvements. For example, a publisher might prioritize periodic
reviews of their top-selling EPUB Publications to ensure they remain maximally usable to the
widest possible audience.
4. Optimized Publications
This section is non-normative.
Although WCAG [WCAG2] provides a general set of guidelines for making content broadly accessible,
conformant content is not always optimal for specific user groups. Conversely, content optimized for a
specific need or reading modality is often not conformant to WCAG exactly because it targets a specific
audience.
For example, an EPUB Publication with synchronized text and audio can contain a full audio recording of
the content but limit the text content to only the major headings. In this case, the EPUB Publication is
consumable by users who needs to hear the content (i.e., they can listen to the full publication and can
navigate between headings), but it is not usable by anyone who cannot hear the audio.
In other words, when EPUB Creators optimize an EPUB Publication for specific reading modalities, the
failure to achieve a WCAG conformance level does not make it any less accessible to the intended
audience.
Defining requirements for optimized publications is outside the scope of this specification, as is
formally recognizing other standards and guidelines that address these specific needs. The general model
of this specification can be used as a basis for identifying how an EPUB Creator has optimized their
content, however.
In particular, if an EPUB Publication meets the requirements of an optimization standard, the following
best practices are recommended:
The EPUB Publication should meet the discovery metadata requirements of
this specification so its accessible properties are machine-readable.
The EPUB Publication should identify the standard or guidelines it follows in a
conformsTo property in accordance with [DCTERMS] so this information can be made
available to users.
If the standard does not define conformance values for the conformsTo property, EPUB
Creators should use a URL [URL] to where the standard is publicly available so users can look up
the specific details of the standard.
If the identifier is not sufficient for a user to understand conformance (e.g., the guidelines are
not publicly available), EPUB Creators should provide additional information about they have
optimized the content in the accessibility
summary.
When creating guidelines for optimized EPUB Publications, it is recommended that these practices be
integrated as a formal requirement for conformance.
Although EPUB Creators do not have to follow the recommendations in this section to conform to this
specification, some jurisdictions require EPUB Creators to follow similar practices. Directive
2019/882, for example, includes similar requirements for digital publications distributed in
the European Union.
The creation of accessible EPUB Publications does not guarantee that the publication will be obtainable
or consumable by users in an accessible fashion. Depending on how EPUB Creators distribute their EPUB
Publications, other factors will influence their overall accessibility. For example, an accessible
interface for locating and obtaining content is an essential part of the distribution process, as is the
ability to search and review accessibility metadata.
While much of the distribution process is outside the control of EPUB Creators, so outside the scope of
this specification, there are factors an EPUB Creator can control. For example, while an EPUB Creator
typically does not control the accessibility of the digital rights management (DRM) scheme applied to
their EPUB Publications, they do control what usage rights to apply to their EPUB Publications. So even
though a DRM scheme may allow an Author to block access to the text of the publication, the EPUB Creator
needs to take care not to apply such a restriction as it could block the ability for assistive
technologies to read the text aloud.
To minimize the effects of distribution on accessibility, this specification advises EPUB Creators adhere
to the following distribution practices:
they must not impose restrictions that impair access by assistive technologies; and
they must include accessibility metadata in the record format required for distribution of an EPUB
Publication (e.g., [ONIX] or [MARC21]) when the format supports such metadata.
Note
A distributor may implement a digital rights management scheme that inherently impairs accessibility
through no fault of the EPUB Creator. Following the guidance in this section does not restrict EPUB
Creators from using such distributors. The intent is only that the EPUB Creator not impair
accessibility by activating a feature that would normally not be active.
6. Privacy and Security
This section is non-normative.
The authoring of accessible content does not introduce any new privacy or security considerations for
users. Meeting accessibility requirements is about optimally using the available technologies, and no
new features are introduced by this specification.
The inclusion of accessibility metadata by EPUB Creators similarly does not introduce security or privacy
issues for the EPUB Creator, as describing an EPUB Publication only provides a general idea of its
suitability for different user groups.
The use of accessibility metadata in reading systems, bookstores and any other interface that can build a
profile of the user, on the other hand, has the potential to violate individual privacy laws. While it
might seem helpful to store and anticipate the type of content a user is most likely to consume, for
example, or how best to initiate its playback, developers should not engage in such profiling unless
explicit permission is obtained from the user and a means of easily removing the profile is
available.
Even in the case where a user assents to the application maintaining information about their
accessibility needs, developers must ensure that this information is kept private (e.g., it must not be
shared with third party advertisers or even with the original publisher).
Developers should also be mindful about storing or mining information about the types of searches a user
performs when searching for content based on its accessibility characteristics. This information can be
used to indirectly profile the abilities of users.
A. EPUB Accessibility Vocabulary
A.1 Overview
A.1.1 About this vocabulary
This vocabulary defines properties for describing the accessibility of EPUB Publications in the
Package Document metadata.
A.1.2 Referencing
The base URL for referencing this vocabulary is
http://www.idpf.org/epub/vocab/package/a11y/#.
This specification reserves the prefix "a11y:" for use with properties in this
vocabulary. EPUB Creators do not have to declare the prefix in the Package Document.
A.1.3 Conformance properties
A.1.3.1 certifiedBy
Definition of the certifiedBy property
Name:
certifiedBy
Description:
Identifies a party responsible for the testing and certification of the
accessibility of an EPUB Publication.
Allowed value(s):
xsd:string
Cardinality:
One or more
Example:
<metaproperty="a11y:certifiedBy">
Accessibility Testers Group
</meta>
A.1.3.2 certifierCredential
Definition of the certifierCredential property
Name:
certifierCredential
Description:
Identifies a credential or badge that establishes the authority of the party
identified in the associated certifiedBy
property to certify content accessible.
Allowed value(s):
xsd:string
Cardinality:
Zero or more
Extends:
a11y:certifiedBy
Example:
<metaproperty="a11y:certifiedBy"id="certifier">
Accessibility Testers Group
</meta><metaproperty="a11y:certifierCredential"refines="#certifier">
DAISY OK
</meta>
A.1.3.3 certifierReport
Definition of the certifierReport property
Name:
certifierReport
Description:
Provides a link to an accessibility report created by the party identified in the
associated certifiedBy property.
<metaproperty="a11y:certifiedBy"id="certifier">
Accessibility Testers Group
</meta><linkrel="a11y:certifierReport"refines="#certifier"href="https://example.com/a11y-report/"/>
B. Change Log
This section is non-normative.
Note that this change log only identifies substantive changes since EPUB Accessibility 1.0 — those that affect the conformance of EPUB Publications or are
similarly noteworthy.
28-Sep-2021: The section on optimized publication has been made informative and rewritten to
highlight best practices for identifying conformance to such standards. See pull request 1833.
23-Sep-2021: Added section explaining effects of internationalization on techniques used. See issue 1790.
07-Sep-2021: Added refines attribute to certifier metadata examples to show the
expected linkage. See issue 1789.
07-Sep-2021: Added explanation that the dcterms:date property can be used to indicate
when an evaluation was performed. See issue
1590.
09-June-2021: Clarified that a pagination source must not be specified when page break markers
and/or a page list are included in a digital-only publication. See issue 1599.
29-Apr-2021: Change conformance identifiers to use hyphens and dashes so they are not confused for
plain language strings. See issue
1455.
26-Mar-2021: Added informative section detailing when to re-evaluate EPUB Publications. See issue 1470.
12-Mar-2021: Changed the distribution section to informative but added a note that the requirements
must be followed where required by law (e.g., in the EU). See issue 1487.
08-Mar-2021: Add objective for the sequence of par and seq elements in
media overlay documents to reflect a logical reading order. See issue 1556.
05-Mar-2021: Added recommendation that page markers be included for all pages of content reproduced
from source and best practice to include markers for all pages in the source. See issue 1502.
05-Mar-2021: Added recommendation that page list include links to all pages of content reproduced
from source and best practice to include links to all pages in the source. See issue 1503.
05-Mar-2021: Restructured the EPUB Requirements section to split out the individual objectives that
were grouped together under the Page Navigation and Media Overlays headings. See issue 1458.
25-Feb-2021: Replaced the IDPF URLs used to report conformance to the 1.0 specification with more
flexible text strings. See issue
1455.
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).
01-Feb-2021: Changed the recommendation that media overlays conform to the requirements of the EPUB
specification to a requirement. See issue
1486.
17-Nov-2020: Added the refines attribute to the certifierCredential and
certifierReport properties and examples. See issue 1410.
16-Nov-2020: References to the optional accessibility control and API metadata have been removed
from the discoverability section. These metadata properties are more applicable to Reading Systems.
See issue 1327.
26-Sept-2020: The revisions made to the Accessibility 1.0 specification as part of publishing it as
an ISO standard have been incorporated into the initial draft text.
C. 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)