This document, EPUB Fixed Layout Accessibility, outlines the goals for EPUB accessible fixed layout ebooks while acknowledging the challenges unique to the fixed layout format.
EPUB fixed layout publications, or publications where the print layout is preserved in the digital edition, have been around since before EPUB 3.0.1. These publications span a number of genres and types, from comic books, cook books, children's books, and more.
An accessible fixed layout EPUB file is one that meets the accessibility requirements of the Web Content Accessibility Guidelines 2.x level AA [[wcag2]] and EPUB Accessibility 1.1 [[epub-a11y-11]], including color contrast, reading order, font layout, structural navigation, accessibility metadata, and text alternatives. Not all WCAG success criteria are applicable to EPUB documents, a more detailed list can be found in section 1.4.
The main motivation behind creating fixed layout publications is the need to preserve the print layout of the book, either because of the layout's importance to the text (i.e. complex diagrams) or it's artistic purpose (i.e. illustrated text). These publications can often be partially or completely inaccessible to people with disabilities, especially disabilities affecting vision or visual processing. However, the visual nature of fixed layout publications can also offer advantages for disabled readers. Graphic and visual design is about much more than making things look pretty, and well-designed publications can create reading experiences that aid in increasing understanding, information retention, conveying complex ideas, and more.
This note serves to help EPUB creators, publishers, and reading systems address some of the common accessibility issues found in fixed layout content including navigation, reading order, and text alternatives. This document is a companion to EPUB Accessibility 1.1 [[epub-a11y-11]], specifically for fixed layout publications. The recommendations made in EPUB Accessibility 1.1 [[epub-a11y-11]], EPUB 3.3 [[epub-33]], and EPUB Reading Systems 3.3 [[epub-rs-33]] are applied and extended here.
In addition to the recommendations in this document, the Publishing Maintenance Working Group's Fixed Layout Accessibility Task Force is producing an accompanying techniques document to cover the technical side of fixed layout accessibility.
This document provides guidance and best practices for meeting the requirements of EPUB Accessibility 1.1 [[epub-a11y-11]] for fixed layout publications, in particular with respect to meeting WCAG 2 success criteria [[wcag2]]. It is not a new standard for document accessibility.
This document does not cover WCAG success criteria that do not typically apply to fixed layout content or that cannot be accommodated by fixed layouts. For example, the needs of people with low vision or learning disabilities that rely on the transformation of text (i.e., dyslexia) are still difficult to accommodate in fixed layout content.
Success criteria categorized as Level AAA are also out of scope, as these are typically considered aspirational for conformance purposes. EPUB creators may still want or need to meet the criteria not covered by this document, and are encouraged to do so when possible.
This document also outlines reading system considerations specific to accessibility for fixed layouts, and methods reading systems can apply to make content more accessible. It is not a general guide to making reading systems, their user interfaces, or user experiences accessible.
The Publishing Maintenance Working Group recognizes that making fully accessible fixed layouts presents unique challenges, and may not be possible in many cases. That should not be used as an excuse not to make fixed layout publications as accessible as possible.
EPUB creators who have to meet specific accessibility conformance requirements may find that reflowable publications are the only option at this time.
We want to recognize these challenges for EPUB creators, and in this document will outline some recommendations for producing more accessible fixed layout content. We encourage EPUB creators to explore the full range of options for accessibility that digital publications present, even when creating fixed layout publications.
WCAG [[wcag2]] is structured around four main principles: Perceivable, Operable, Understandable, and Robust. These principles are the foundation of web accessibility and a helpful way to group and understand the guidelines and success criteria required to make content accessible. Not all WCAG success criteria apply to fixed layout content, and fixed layout cannot meet all success criteria that apply.
We will use the principles to demonstrate how accessibility success criteria relate to fixed layout content.
Content must be presented and built in a way that allows it to be perceivable to different senses. This principle requires fixed layout content be built in a way that supports multiple reading methods - visual, audible, and tactile. This principle and its related success criteria are achieved by providing text alternatives for images, using proper markup to structure content, and ensuring visual content is well contrasted and designed.
These are the most applicable success criteria for fixed layout content:
Content and navigation must be operable, built in a way that makes it usable for all users. This principle, when applied to fixed layout content, is achieved through consistent navigation and content structure.
These are the most applicable success criteria for fixed layout content:
Content must be understandable. This principle has limited application to fixed layout content aside from the importance of proper language labelling.
These are the most applicable success criteria for fixed layout content:
Content must be robust enough to be interpreted by a variety of user agents, reading systems, and assistive technologies. For fixed layout content, achieving this principle requires the EPUB file to be well-formed and all content must use proper markup.
These are the most applicable success criteria for fixed layout content:
EPUB 3.3 [[epub-33]] supports multiple methods for content development, particularly for fixed layout content. The two primary methods are to use XHTML and SVG for building EPUB content documents. A third method used in many EPUB fixed layout books is to reference image files in the spine of the EPUB file. We will discuss the accessibility considerations for all three methods in this document.
In addition to the core technologies mentioned in the EPUB 3.3 recommendation, EPUB accessibility may also require the use of the Accessible Rich Internet Applications [[wai-aria-1.2]] and Digital Publishing WAI-ARIA [[dpub-aria-1.1]] recommendations.
A key concept of EPUB is that an EPUB publication consists of multiple resources that can be completely navigated and consumed by a person or program in some specific order. - 1.2.1 Reading Order EPUB 3.3 Overview [[epub-overview-33]]
Whereas many reflowable publications have an obvious reading order, or logical progression through their content, fixed layout publications are often more complex in their design and layout and may consist of multiple readable objects on the same page.
For viewers of the visual page, the reading order can be inferred by various visual triggers including:
In addition, there may be text and image objects on the fixed layout page which are not required to be included in reading order, such as:
WCAG [[wcag2]] has several success criteria that relate to order of content that should also be considered:
If a blind user, who reads the page with a screen reader that follows the source order, is working with a sighted user who reads the page in visual order, they may be confused when they encounter information in different orders. A user with low vision who uses a screen magnifier in combination with a screen reader may be confused when the reading order appears to skip around on the screen. A keyboard user may have trouble predicting where focus will go next when the source order does not match the visual order. - Making the DOM order match the visual order
There may be cases when text appears on the page but is unnecessary, duplicated or otherwise confusing for it to be added to the reading order, e.g. page numbers, running headers and footers, or text used for visual effects.
See the techniques document for guidance on how to apply this recommendation.
Fixed layout documents can be presented as synthetic spreads where two pages are arranged side-by-side. As each page of the fixed layout document is a separate XHTML document, it is expected that the reading order of the EPUB flows from one page to the next. Even if the content is presented in a synthetic spread, the reading order should not require that the reader move between pages to read the content in order.
If the text must be read in this way, the only solution to maintain the correct reading order is to convert the double page spread in to a single landscape page that contains the entire content of the spread and for the EPUB to be rendered as single pages.
Images are often an integral part of fixed layout publications. Fixed layout publications sometimes consist entirely of images, in the case of comics, or images may be used as backgrounds to a story, as in children's books. Fixed layout content where images serve as both the content and the layout pose a particular challenge for EPUB creators interested in accessibility.
Ensuring that the information conveyed in the images is available to users who may not be able to perceive the image or may have difficulty processing it, is consequently of high priority in making fixed layouts as accessible as possible.
WCAG [[wcag2]] has several success criteria that apply to the presentation and accessibility of images:
The basic requirements for all images are to provide alternative text and extended descriptions when they contain information necessary to understanding the publication, which applies to fixed layouts. For example, while a reader may be able to follow the dialogue of a story when it is overlaid as text, only the placement on image might give context to what character is saying what.
One challenge with fixed layouts is finding ways to describe the image and provide context given that there is no extra area on the page users can access in which to place a description. Another challenge is for content where the text is rasterized as part of the image, which can be unavoidable for content where the text is hand-drawn or part of the image. An additional challenge is fixed layout content where the pages or spreads are made up of multiple images that may require individual descriptions.
Image descriptions and alternative text do have limits in their ability to translate image content to text, those limitations include the ability to adequately map the flow of action on a page to text, or translation of visual effects to textual equivalents. Work continues in this area to improve this experience, and we will note gaps in the sections below.
It is also important to mention decorative images, or images that provide no semantic value or meaning to the content. These images do not require alternative text, and in some cases, providing it may pose a challenge or frustration to the reader.
Describing images within a fixed layout book will somewhat depend on the type of book these images are within. For example describing a childrens picture book will be quite different than if this is a fixed layout graphic novel such as a comic book.
Not all details are needed in writing alternative text for images, and what you do describe relies heavily on context. For example, if the image is described in the surrounding text, you only need to briefly describe it in the alternative text.
Depending on the complexity of the image this may require complex description with one of the following formats:
If an image splits over two pages, put the full image description of both images in the first image and in the second image reference back to the first. See Multiple Page Spreads.
If there are a group of images in sequence, you only have to describe details in the first image. In the proceeding images only mention what has changed.
Some fixed layout publications are constructed exclusively from image files in the spine. While this is not a recommended method in EPUB 3.3, some markets do use this format. Another method is to put image files into XHTML documents, but only the image file and no other content. Both of these methods fail to meet basic accessibility requirements, especially images in the spine.
The legibility, or readability, of fixed layout content is an important contributing factor to its accessibility, particularly for users with low vision, cognitive, or learning disabilities. As text in a fixed layout document is unalterable, it is important to consider best practices in putting together clear, legible documents. EPUB creators are reminded that ebooks can be read on a number of different screen sizes and devices, many that will be smaller than the print version of the page. Designs for fixed layout content should take into account these smaller screen sizes and their impact on legibility and layout. This section will focus on what to consider when constructing more legible fixed layout publications.
WCAG [[wcag2]] has a number of success criteria relating to the presentation of content:
Due to the formatting constraints presented by fixed layout content, some success criteria relating to the presentation of content can be challenging or impossible to meet.
The following Success Criteria relate to the visual adjustability or layout of content:
Aside from the ability to zoom, most fixed layout reading systems do not allow the reader to adjust the visual presentation of the content by resizing text or adjusting the text layout (letter, word, line spacing, or margins). EPUB creators also have the ability to set specific orientation settings for fixed layout EPUBs.
These limitations in how EPUB reading systems display fixed layout content mean that this content cannot meet some of these requirements, specifically, 1.3.4 Orientation and 1.4.10 Reflow. These limitations also result in an automatic failure of 1.4.4 Resize Text and 1.4.12 Text Spacing. These constraints mean EPUB creators should consider these requirements as much as possible during the design of the content. EPUB creators can do this by considering:
Many of the Success Criteria mentioned previously focus on the content being programmatically available to the user (accessible to assistive technology), but the same principles that are communicated programmatically can also be communicated visually. For example, most content design makes a visual differentiation between heading and body text, as a visual indicator of their relationship. Programmatically, we use elements like <h1> and <p> to achieve this. Visually, we do this by styling headings with larger text, different colors, or a different font face.
Success Criteria like the following can be achieved with conscientious visual design:
Success Criteria 1.3.1, 1.3.2, 2.4.6, and 3.2.4 all cover ensuring content is programmatically related and identifiable as it is presented visually. That visual presentation is essential for all kinds of content, but for fixed layout EPUBs, can be even more essential.
Due to the constraints fixed layout presents, and the potential devices fixed layout content can be used on, EPUB creators should consider how the visual design of their content may present challenges to users with low vision, cognitive, or learning disabilities. These recommendations are meant to be informative and are not required to achieve accessibilility conformance.
When designing this content, consider the following:
EPUB creators should also consider testing their content during the design and development process on a number of different screen sizes and zoom levels, to help understand any potential challenges a reader may face.
Color is an important part of visual design, and can be benficial to legibility and understanding, when used properly. Success Criteria 1.4.1 and 1.4.3 require that color be used appropriately and be of sufficient contrast.
When using color in content design, consider the following:
Non-text content like images, videos, visualizations, or graphs can be an essential part of understanding the book content. For some readers, non-text content can increase their ability to comprehend or synthesize the text content or subject matter. When designing the book, it's important to consider the formatting and placement of this content to maximize the benefit to the reader.
To meet Success Criteria 1.1.1 and 1.4.5, it's required to provide textual alternatives for the content. For 1.4.5 in particular, it's important to consider whether the textual content in the image needs to be an image, or might be incorporated into the surrounding content.
For users that are engaging with the content visually, it's important to consider:
There is no single font that meets the legibility needs of all users, but considering certain font characteristics to increase legibility is possible. When planning font selections in fixed layout publications, consider the following:
There is no font size guideline in WCAG [[wcag2]] stating a specific font size, and the standard default font size in most desktop and mobile browsers is 16px for body text (i.e. in a p element). This size is sufficient for most content, and headings should be based off of it by using em or rem sizing in CSS [[css2]]. If content contains a great deal of text, it is also recommended to consider a larger body font size like 18pt to ensure readability.
WCAG success criteria 1.4.4 Resize Text does specify that text needs to be able to resize to 200% of its default size without loss of readability or functionality. In fixed layout content, this would be achieved by the user zooming into the page 200% or more.
Content creators should also ensure font size patterns are consistent throughout the content, to assist users in differentiating and contextualizing the content.
Depending on the chosen font, it might be necessary to consider the weight of the font to make it more legible. A font weight of 400 is considered normal or regular, but depending on the font face, may be too light. A font that is too light can disappear into the background of a page, especially if factors like clarity or contrast are not considered. A font weight of 700 is considered bold, and would be more readable, but overusing a bold typeface can present its own issues for legibility.
Selecting a font face for your content can depend on a number of factors. When choosing a font for fixed layout content it is important for content creators to consider readability because a user will not be able to alter the font face to suit their needs or preferences.
One of the most important factors for the readability of fonts relates to character differentiation. Character differentiation in a font is a strong indicator of readability, specifically for characters that have similar shapes in a font face. In the Latin alphabet, letters like I (upper case "i") and l (lower case "l"), b and d, or a o and e can look very similar to one another depending on the style of the font. The same issue is possible in fonts for other alphabets, particularly when glyphs are similar in appearance or use similar elements.
Media content such as audio, video, and interactive elements present both an opportunity and a challenge for fixed layout content. When media content is implemented with accessibility in mind, it can greatly improve the reading experience of a book. Done poorly, it can be a major barrier to access.
Media content can be incorporated into fixed layout EPUBs in a variety of ways. When working with media content in EPUB, it is important to consider WCAG [[wcag2]] criteria relating to media accessibility:
Media overlays allow EPUB creators to create an enhanced textual reading experience by synchronizing text and pre-recorded audio content. Media overlays in EPUB (reflowable or fixed layout) are not equivalent to audiobooks. Media overlays are also not a replacement or substitute for features like screen reader support or text to speech. Currently, media overlays in EPUB only support synchronizing audio media with textual content.
The provision of synchronized text-audio playback helps address various user needs. It not only enables a seamless visual and auditory reading experience from beginning to end of an EPUB publication, but is useful to users who require audio playback (e.g., who cannot see the text or have difficulties reading visually) or who benefit from reading with text highlighting (e.g., readers with dyslexia).
Unlike purely linear listening experiences, EPUB with synchronized text-audio playback preserves the user's ability to navigate around the publication, such as via the table of contents, and also introduces audio-centric reading features like phrase navigation, and ways to control which parts of the content are read aloud.
In order to offer users greater control over content presentation, EPUB creators need to add structure and semantics so that the reading system has the necessary context to enable this type of user experience. With greater context, a reading system can provide the ability to skip past secondary content that interferes with the primary narrative and escape users from deeply nested structures like tables.
Adding structure and semantics to synchronized text-audio playback 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.
EPUB Accessibility 1.1 [[epub-a11y-11]] recommends the following objectives for content with synchronized text-audio playback:
Accessible alternatives must be provided for all prerecorded audio and video content in an EPUB, with the exception of audio synchronized to the text through a method like media overlays.
The following success criteria apply to media content inserted into the publication outside of media overlays:
For media that is audio-only, it is recommended that the EPUB creator provide an accompanying text-based alternative. Depending on the purpose and type of content, this alternative can be something like a transcript, a description, or a captioned video. For example, if the audio content is a music track that accompanies the book content, the alternative might either be the name of the song, a description of the song, or the lyrics. For content like an audio recording of a conversation or speaker, it is recommended to use a transcript that identifies the speakers and what is being said.
For media that is video-only, it is recommended to provide an audio description of the content, as well as a text-based version of that description. This description should include everything happening in the video, including descriptions of the setting, expressions, and any text that may appear on the screen that is required for understanding the content. The audio description should be its own track within the video player.
For media that has both audio and video, all of the recommendations for audio-only and video-only apply.
In EPUB 3.3 [[epub-33]], resources referenced in the [[html]] track element (e.g., captions, audio descriptions, and subtitles) are considered Exempt Resources, which means file formats may not have guaranteed EPUB reading system support, but also do not require a fallback. It is important to test your EPUB file if it contains any of these exempt resources, to ensure compatibility.
If an EPUB creator is considering including animations and motion-based content, they should consider the following success criteria:
Animations, auto-updating content, or content in motion (e.g., blinking, scrolling) can distract users, cause discomfort, or even trigger conditions like migraine. When these features are included, it is important for EPUB creators to provide a mechanism that allows the user to stop or hide the animations. EPUB creators should also be conscious that any animations or motion do not contain anything that flashes more than three times in a one second period.
While this document focuses on WCAG recommendations up to level AA, there is a AAA Success Criteria for animations that EPUB creators should consider when designing their book content. 2.3.3 Animation from Interactions recommends that if an interation triggers a motion animation, it should be possible for the user to disable it, unless the motion is essential to the functionality or information being conveyed.
The best way to create an accessible table is to present it as tabular data. This is already documented in the DAISY Knowledge Base with directions on creating semantic tagging for tables.
WCAG [[wcag2]] has several success criteria relating to tables:
If the table needs to remain an image, another option is to use alternative text, the figure or details elements, or adjacent text content to describe the table. A caption could be used as a summary of the table, and the alternative text or adjacent content would dive deeper. You would start with describing what the header row is followed by what is presented in each row. You could then dive deeper and list all the data as it appears in reading order.
Depending on the complexity of the image this may require complex description with one of the following formats:
Provide an extended description for a table using either aria-describedby or aria-details.
The advantage of aria-details over aria-describedby is that it allows users access to the markup of the linked description (which could be the table markup if you put it, for example, inside a details element to collapse it). The current drawback, however, is that there isn't great support yet for the attribute. Expanding details elements within a fixed layout page is also likely to disrupt the page when users click on it (unless you find a way to reliably position it offscreen, but then that limits who can access it).
The aria-describedby attribute's big drawback is that it turns the description into one long text string that users have to listen to. There's no way to navigate the columns and rows or have headers read out, so it's likely going to be very difficult for users to make sense of except for very simple and very small tables.
The package metadata used in the EPUB is the primary method for a reading system to determine whether content is fixed layout or reflowable. In addition to identifying the pagination mode with rendition:layout, package metadata can also allow the EPUB creator to have some control over other display characteristics.
These display characteristics include:
rendition:orientation - the orientation of the book, can be landscape, portrait, or autorendition:spread - the spread settings of the book, can be none, landscape, both, or autorendition:page-spread-* - spread settings for individual spine items, can be left, right, and centerThe default value for the orientation and spread properties is auto, which means that the reading system settings or defaults take effect.
It is advised that EPUB creators must not set a specific orientation property, as this can interfere with user device preferences in accordance with WCAG Success Criteria 1.3.4. It is especially important for users who may be unable to change the orientation of their device to match the content settings.
Books with accessible elements require metadata to indicate how they are accessible, and if they present any hazards to the reader. A full description of accessibility metadata in EPUB can be found in section 2 of EPUB Accessibility 1.1 [[epub-a11y-11]] and the Schema.org Accessibility Properties for Discoverability Vocabulary.
The DAISY Knowledge Base also provides excellent guidance on the usage and definitions of Schema.org metadata in an EPUB file. In this section, we have provided some examples of what this metadata might look like depending on different fixed layout use cases.
A common use for fixed layout is children's picture books, which feature expressive illustrations and small amounts of text. In this example, this is a book where the EPUB creator has done everything needed for accessibility.
Cookbooks are commonly formatted using fixed layout, due to their highly visual layout. In this example, the publisher has created a cookbook that meets accessibility requirements, including providing a detailed table of contents and index.
This example is for a children's book that uses media overlays. The audio for the book contains a potential sound hazard, so it is declared in accessibilityHazard and further detail is provided in the accessibilitySummary.
This example features a textbook that includes video content. The video content does not include audio descriptions, but as described in accessibilitySummary, the EPUB creator fully describes the video content in surrounding text. There are potential hazards due to the type of video content.
As EPUB creators work on remediating their catalogues, some books may not be fully accessible or tested against WCAG requirements. It is helpful for readers to know the status of a book, even if it is not yet accessible, so they can make informed decisions when buying or borrowing.
<meta property="schema:accessMode">visual</meta>
<meta property="schema:accessModeSufficient">visual</meta>
<meta property="schema:accessibilityFeature">unknown</meta>
<meta property="schema:accessibilitySummary">
This publication has not been accessibility tested, or had remediation work done. If there are any questions about this book's content, or an urgent need for an accessible edition of this book, please contact us at [help]@[publisher].com.
Manga is commonly distributed in fixed layout EPUB format, either with images as spine items or embedded in individual XHTML files for each page. Most manga features images where the text is part of the image and not provided separately.
An EPUB reading system can take many forms. It might have a small or big visual display area for visually rendering the content to users, or it might only provide audio playback or tactile display. It can be dedicated to the EPUB format or handle many formats. It can depend on an operating system ecosystem that includes assistive technologies or be self-sufficient on a dedicated reading device. There is no single set of rules that applies to all reading systems, and this section presents the most important aspects of reading a fixed layout publication to take into consideration.
This section is composed of three parts:
As fixed layout files are not fully supported by all reading systems but may be displayed without rendering the content as specified, information about what features are supported should be given to the user. This precaution is important to avoid deception of the user and misunderstandings about the format and its capabilities.
For example, a user could be informed whether the reading system:
Any reading system must take into consideration the recommendations listed in the Accessibility section of the EPUB Reading Systems 3.3 document [[epub-rs-33]].
Fixed layout EPUBs are composed of a large variety of EPUB features, often using an extended set in comparison to reflowable EPUBs. To ensure accessibility in the reading system, this list of recommendations should be considered:
A reading system should provide information on accessibility metadata provided by the EPUB file in the OPF. Guidance for key information and proposed wordings are provided by the W3C Publishing Community Group Accessibility taskforce report: User Experience Guide for Displaying Accessibility Metadata.
Assistive technologies are user agents that help users with specific needs to get access and interact with the content. They are often used in combination with a reading system and an operating system, therefore particular attention must be provided to make sure no blocking happens.
This support happens through API integration, ensuring that the accessibility tree, including support for roles, states and properties, is exposed to the underlying operating system's accessibility API. This means that users can fully interact with the content when using assistive technologies. Reading system developers also need to integrate the accessibility properties and values provided by the Accessible Rich Internet Applications 1.1 [[wai-aria-1.1]] and Digital Publishing WAI-ARIA 1.1 [[dpub-aria-1.1]] recommendations.
The User Agent Accessibility Guidelines [[UAAG20]] also provide information on building user agents that integrate with assistive technologies.
As the purpose of fixed layout is often the representation of the printed page, with constraints on viewport and display, a reading system with an accessible fixed layout reading experience must enable zooming of the page. This must be possible without assistive technology and guarantee that no content or functionality is lost.
Resizing a page should not affect the original proportions, acting like a magnifying glass and should allow the user to zoom in at least 200 percent.
The following Success Criteria relate to the visual adjustability of content:
Fixed Layout pages generally include one or more images, therefore it should be possible to view each of them fullscreen.
Alternative text is usually hidden from visual reading and exposed to assistive technologies and non-visual reading methods like text to speech. The addition of visual display for those contents should be considered carefully as, in complex layouts including overlapping images, it may lead to overlays masking content.
Extended descriptions, including long and structured content that cannot be authored as alt attributes, are usually provided as links to appendices or included into foldable elements like details. Even if they are not often present in fixed layout due to the complexity of authoring them, reading systems must make sure that interactions are available.
WCAG [[wcag2]] has several success criteria that apply to the presentation and accessibility of images:
Often used in educational or children's literature context, fixed layout EPUBs can contain synchronized audio narration as defined in EPUB 3.3 Section 9. Supporting this feature is highly recommended for reading systems.
Recommendations for media overlay support in reading systems is provided in the EPUB Reading Systems 3.3 Media Overlay processing section.
Despite all efforts provided to ensure that a reading system offers rich accessibility features for fixed layout content, a file may become inaccessible due to content protection restrictions blocking access to accessibility APIs. Reading system developers must ensure that the protection method used preserves all the accessibility features described in this document.
If this is not the case, users must be informed of the limitations created by the protection method used to protect the file.
In cases where the EPUB creator has included fallbacks for potentially unsupported content (e.g. MathML, audio, video), the reading system should support fallbacks. EPUB creators should follow the guidance provided in the EPUB 3.3 Manifest Fallbacks section.
Alternative rendering methods for ebook content are methods of rendering beyond the visual, specifically auditory and tactile rendering (i.e., screen reader output or braille). While fixed layout formatting is often used to represent highly visual content, not all reading systems support visual display, and when visual display is available, screen sizes may be limited. Therefore, many reading systems might avoid supporting fixed layout content due to concerns about a poor reading experience. In addition to concerns about rendering, it must also be considered that many users face difficulties consuming and navigating complex fixed layout content. Alternative rendering methods should be considered as a replacement or addition to fixed layout rendering.
If the fixed layout publication does not conform to the recommendations made in this document, or WCAG [[wcag2]], providing alternate renderings of the content may result in an unusable or poor reading experience. Content that is not formatted in conformance with WCAG may result in output that has an incorrect reading order, broken sentences, or choppy pronounciation. The user should be informed if the content does not have accessibility metadata that would provide clarity on whether alternate renderings are supported, such as dcterms:conformsTo with a value for WCAG, or metadata values that conform to properties like Supports nonvisual reading from the User Experience Guide for Displaying Accessibility Metadata.
The User Experience Guide for Displaying Accessibility Metadata is currently a draft document and is subject to change.
There are ongoing discussions about transforming visual publications into reflowable textual content for complete AA compliance. While these are not in production yet, by creating our fixed layout with logical reading order, full image descriptions, and good semantics and structure where possible we are preparing our files in the best way for these future developments.
Not all reading systems are built on an operating system providing assistive technology and not all readers with specific needs related to reading impairments are comfortable with using complex assistive technologies. Therefore text to speech (TTS) functionality is a strong requirement for a reading system claiming to provide fixed layout accessibility support.
How a reading system implements TTS will depend on multiple factors, including platform, underlying operating system, or technical feasibility. There are a variety of TTS APIs and speech engines available. An example is the Web Speech API from W3C Web Platform Incubator Community Group. Reading system developers can test their support of TTS with Epubtest.org's Fundamental Accessibility Tests Read Aloud.
The Accessible Name and Description Computation draft specification is another useful reference in implementing a text to speech experience.
This document was a group effort, with many people generously contributing their time, expertise, and insight into its development. Special thanks must also be given to those that contributed sections of this document, including Gautier Chomel (EDRLab), Charles LaPierre (Benetech), and Susan Neuhaus (NeuStudio).
The following members of the Fixed Layout Accessibility Task Force also contributed to the development of this document: