This document, EPUB Fixed Layout Accessibility, outlines the goals for EPUB accessible fixed layout ebooks while acknowledging the challenges unique to the FXL format.
EPUB fixed layout (FXL) 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 level AA [[wcag2]] and EPUB Accessibility 1.1 [[epub-a11y-11]], including color contrast, reading order, font layout, structural navigation, metadata, and text alternatives.
The main motivation behind creating fixed layout publications is the need to preserve the print layout of the book, either because of it's importance to the text (i.e. complex diagrams) or it's artistic purpose (i.e. illustrated text). However, these publications are often partially or completely inaccessible to people with print disabilities.
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. All 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 FXL accessibility.
Fixed layout publications present some unique challenges for accessibility. The requirements laid out in EPUB Accessibility 1.1 [[epub-a11y-11]] recommend WCAG 2 level AA [[wcag2]], but for some use cases in fixed layout, that might not be possible without changes to the content. In this document, we will align recommendations with WCAG 2 level AA where possible, but will exclude success criteria that do not apply to fixed layout content.
In particular, the needs of people with low vision or learning disabilities that rely on the transformation of text (i.e. dyslexia) are still almost impossible to accommodate in fixed layout content. EPUB creators concerned about this may choose not to use fixed layout.
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.
Reading systems also play a role in presenting accessible content. This document will outline considerations specific to accessibility for fixed layout in reading systems, and methods reading systems can apply to make content more accessible.
WCAG [[wcag]] 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.
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 all of a user's 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.
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.
Content must be understandable. This principle has limited application to fixed layout content aside from the importance of proper language labelling.
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.
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 FXL 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.
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, section or chapter headings which are already part of the publication’s structure or text used for visual effects.
Fixed layout documents can be presented as synthetic spreads when a left and right page are presented together as a spread. As each page of the fixed-layout document is a separate XHTML document it is expected that reading order moves through there document from left to right (when using left to right page progression) but is not possible for the reading order to move from the left to the right and then back to the left page again.
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. The other 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.
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.
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.
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.
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.
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 FXL EPUBs.
These limitations in how EPUB reading systems display FXL content mean that this content is exempt from some of these requirements, specifically, 1.3.4 and 1.4.10. These limitations also result in an automatic failure of 1.4.4 and 1.4.12. These constraints mean EUPB 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 colours, 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 FXL presents, and the potential devices FXL content can be used on, EPUB creators need to consider how the visual design of their content may present challenges to users with low vision, cognitive, or learning disabilities.
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 and 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.
TBD
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 and caption or ARIA roles to describe the data in logical reading order. The caption could be used as a summary of the table, and the alternative text 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. And expanding details element within a fixed layout page is also likely to wreak a bit of havoc 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 and hazards to the reader.
The schema.org property accessibilityFeature is used to define all accessibility features within the book.
A few values that could apply to a fixed layout book might be:
alternativeText - Images are described with alternative textlongDescriptions - Complex images are described in detailreadingOrder - Reading order of elements is the same between visual presentation and non-visualCertain accessibilityFeature properties, like displayTransformability should not be used with fixed layout content.
The schema.org property accessMode is used to define the ways in which this book can be consumed be that visual, textual, auditory, or tactile.
A picture book without live text would only have an accessMode of visual.
A fixed layout book which contains both text and images would have two separate accessModes defined.
The schema.org property accessModeSufficient is used to define the combinations in which this book can be consumed be that visual, textual, auditory, or tactile.
For picture books with no text, or no alternative text, the way one would consume this would be completely visually so having accessModeSufficient of visual would be solely defined.
For fixed layout books that have both visual and textual elements having accessModeSufficient of visual,textual would be appropriate. In addition, if the fixed layout book is primarily images that are fully described, textual would also apply, as this implies the boook is Screen Reader Friendly and can be fully read by assistive technology.
If a fixed layout book has all images fully described then having accessModeSufficient of textual would be appropriate which implies this book is Screen Reader Friendly and can be fully read by assistive technology.
The schema.org property accessibilitySummary is a human readable statement on how accessible or inaccessible the book is.
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 2.0.
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.
Fixed Layout pages are generally composed of 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.
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.
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, readingOrder, or ttsMarkup.
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.