This page is provided for informational purposes only. It is not an official document for Section 508 compliance, and should not be referenced as such. The purpose of this page is to facilitate understanding of how to create EPUB 3 publications that meet the Section 508 guidelines.
Section 508 of the US Rehabilitation Act requires that Federal agencies make their electronic and information technology accessible. EPUB 3 publications can be created to meet and exceed the guidelines set out in this legislation for organizations required to meet this mandate, whether federal agencies or organizations that provide products or services to such agencies.
Content creators must be committed to an accessible workflow and follow all best practices outlined generally here and throughout this site, however, as EPUB 3 publications are not accessible by nature of their existence alone.
The following paragaphs of Section 1194.22 apply to all ebook content. Provided for each paragraph is a description of the equivalent EPUB markup practice(s), with links to more information in this guide.
Note that WCAG 1.0 criteria are referenced in the implementation sections as Section 508 only provides a mapping to the older guidelines. See the Additional Resources section for possible mappings to WCAG 2.0.
Text equivalents must be provided for all elements that have no text content, including, but not limited to:
Text equivalents should also be provided for MathML content for reading systems that do not support voicing.
Note, however, that decorative images and purely formatting elements (like
manual line breaks and
hr for context changes) should not include text
HTML5 provides the ability to include subtitles, captions and descriptions via the
track element to meet this requirement for audio and video content. Captions and
subtitles can also be embedded directly into multimedia presentation (e.g., when the
object element is being utilised).
In all cases, proper synchronization is necessary to that these alternatives are rendered at appropriate times, but such methods and techniques extend beyond the EPUB format.
Proper semantic HTML5 tagging — enhanced by the
epub:type attribute —
will help you achieve this objective:
asidefor footnotes, etc.).
epub:typeattribute should be used whenever applicable to refine the meaning of multi-purpose tags.
Although testing without a style sheet is generally recommended to validate compliance, an equally useful test to ensure compliance is to navigate the EPUB using text-to-speech capabilities to verify comprehension.
The proper order of elements in the markup is critical to establishing the logical reading order:
figureand similar elements so that it can be skipped over).
Server-side maps are instantiated using the
ismap attribute on an image. When this
attribute is set, a user agent is expected to send the coordinate location clicked back to the
server (to a resource defined in the
href of an ancestor
a tag). There
is no guarantee that an EPUB reading system will honor such behavior, however, as they are not
required to be fully-compliant HTML5 user agents. EPUBs are also not guaranteed to be read in an
online context, making server-side maps a poor markup choice.
Although there is no functionality that a server-side map provides that cannot be duplicated in a client-side map, there is also nothing in EPUB that bars the inclusion of server-side maps. Adding text links for each region of the map is easily achieved, but such intrusive methods for compliance alone should discourage the use of these less accessible map types.
Client-side maps — using the
map element to defined the clickable regions
— are the preferred method for including image maps in EPUB 3 both because of online
availability issues and because such maps can be made natively more accessible for readers with
different preferred modalities.
area in the map must have an
alt attribute identifying its purpose
th element must be used to identify all table header cells, regardless of whether
they occur in the top row of the table, at the beginning or end of each row, or some combination
of both. For tables with multi-row headings, the
thead element should be used to
enclose the header.
Tables should not omit headers and require the reader to determine the meaning from the surrounding context.
headers attribute must be used to when a table cell has a complex table header
(e.g., when a cell has more than one header cell associated with it).
The order in which the header cells are identified correlates to how the reading system will announce them, so always include them in logical rendering order.
Frame sets are not supported in HTML5, removing one obstacle that this guideline was intended to address.
iframe elements in the content, ensure that each is labelled with a
meaningful title that expresses the purpose of its inclusion by attaching a
attribute. Text such as "an inline frame" does not represent a good title.
Ensure that no content flashes on the screen at a rate between 2 and 55 cycles per second. This requirement applies to any content that flashes on the screen, including, but limited to:
Although some flickering in video content may be unavoidable, a best practice is to not include any content that flickers, as it is irritating and distracting to all readers.
EPUB 3 requires that content be fully consumable by the reader, so there should be no need to resort to text-only fallback pages. If a text fallback is being considered, there is likely a better way to accomplish the necessary effect (e.g., progressive enhancement).
When creating SVG-based publications, however, a text serialization in XHTML may be required to fully meet this requirement, as novelization of graphical works is often the only way to fully achieve equivalency.
Progressive enhancement should be used to create fully-accessible scripted publications.
Use of the
noscript element is not recommended, as many non-visual readers use
EPUB requires fallbacks be provided for all non-core media types to ensure that EPUBs render across reading systems. In most cases, the proper inclusion of fallbacks will be sufficient.
As EPUB (and HTML5) lacks a standard video codec and container, a link to the appropriate codec may be necessary to comply with this requirement.
The ability to use enhanced HTML5 and WAI-ARIA form functionality — such as the
aria-invalid attributes — permits content
authors to create highly accessible, device-independent forms in EPUB 3 content documents.
This requirement is oriented more toward Web pages than EPUBs, as the aim is to ensure that readers can jump past the repetitive headers and navigation bars on each new Web site page to get to the content.
One case for EPUBs, however, would be to use
nav elements and ordered lists to
represent all embedded tables of contents. A reader should be able to escape from clearly
identified markup such as this if they choose to skip the navigation links.
ARIA live regions can be used to announce to the reader that a time limit is in effect and to indicate the current countdown time, in addition to any visual indicators.
If more time is permitted, the reader must be notified before the expiration. The announcement should be made in a live region to avoid taking focus away from the current activity (an assertive message would be appropriate, since a passive one may not be announced in time).
Ensure the reader can easily extend the time limit, and to return to their current location. The announcement that time is running out should, for example, provide a device-independent method to extend the timer without changing focus (e.g., through a hotkey).
Although not specific to the EPUB format, the following paragraphs are applicable to audio and video content included in a publication:
The following paragraphs contain requirements to provide alternate modality access to content:
Meeting these requirements will depend on the capabilities of the device the content is to be rendered on (e.g., support for zooming and text enlargement), but EPUB 3 has built-in mechanisms to enable different modalities:
trackelement is available for adding subtitles, captions and descriptions to multimedia content.
The following paragaphs of Section 1194.41 also apply to ebooks. Although most of these provisions relate to organizational requirements, suggestions on ways to enhance EPUBs to accommodate are provided.
Although an EPUB cannot meet this requirement when the user requests an alternate format, an EPUB does allow a wide variety of modalities to be accommodated without need for specialized formats (e.g., text-to-speech playback, refreshable braille display, etc.).
The ability to include ONIX accessibility compliance metadata in an embedded message is one method EPUB 3 provides to meet this criteria.
This organizational support requirement is outside the purview of EPUB 3, but support for the EPUB itself (the internal contact or trusted intermediary) can be specified in the ONIX metadata.