This article is a primer on the choices a user is given, when exporting from InDesign, that will impact the accessibility of an ebook.
Subject(s):
Ebook Production
Resource Type(s):
Step-by-Step
Audience:
Introduction
Before reading this, you might want to review:
You can manipulate InDesign into creating better ebooks a number of ways, ranging from setup tricks to using styles creatively. But many tricks are also buried in the extensive EPUB export options. In this article, we’ll walk you through the choices.
One of the most useful things you can do for the accessibility of your ebook content is also the simplest: Opt for export to EPUB 3 instead of EPUB 2. EPUB is a specification defined by the International Digital Publishing Forum (IDPF), an organization that was folded into and taken over by the W3C in 2017. Maintenance of the EPUB spec is now assumed by working groups within the W3C. The EPUB 3 spec was approved in 2011. EPUB 3 assumes the EPUB 2 spec but takes a slight left turn to a set of definitions that are explicitly accessible. A major goal of EPUB is to facilitate content accessibility through navigation, structural hierarchy, rich media, and semantic HTML.
Under the options at File —> Export —> EPUB (Reflowable), InDesign will default to EPUB 2. The simple action of opting for EPUB 3 amplifies the accessibility of the resulting document. It is not possible to overstate this. Some ebook retailers report that up to 60% of brand-new content is still EPUB 2. The work of having to accommodate that older specification is significant for ebook vendors.
There is nothing wrong with EPUBs made to the EPUB 2 spec, per se, but we would compare it to opting for something flat over something three-dimensional. Please consider selecting EPUB 3 the next time you make ebooks.
When it comes to accessibility, the next, and arguably most impactful, EPUB feature you can build in is the very thing that will give your ebook structure and thus make it easier to use: a linked table of contents (TOC). You can choose to link to an existing TOC style or create a bespoke TOC for EPUB export purposes. The structure you create in an EPUB TOC style will become the navigation document for your ebook. A good navigation that goes several heading levels deep is one of nicest things you can do for readers. It makes it easy to go back and forth in an ebook, and contributes considerably to the usability of any ebook. For print-disabled readers, the fitness of the baked-in navigation document is key to being able to flip through an ebook.
In the Text window, there are couple of notable things. Please be mindful to map lists to the correct HTML for lists. Converting a bulletted or numbered list to text will strip that content of meaning in some contexts. Imagine listening to a list being read as a long run-on sentence without pause and without any indication that it’s a list. It wouldn’t be a good reading experience.
Under the Object tab, you can manipulate InDesign into turning out a responsive ebook — almost despite itself. Asking the export to determine the size of images as relative to text flow, rather than fixed, means that the size of images will depend on the size of the end user’s screen. The CSS definitions will be output in percentages, rather than pixels.
Be mindful not to check “Ignore Object Export Settings,” particularly if you’ve applied semantics, alt text, or grouped items to export as an image.
Under Conversion Settings, we encourage you to export images to JPEG rather than GIF or PNG wherever possible. Using JPEGs results in a more compact EPUB. The size of the EPUB contributes to the usability of the content; i.e., larger is harder and clunkier to use, especially on older devices.
The HTML & CSS tab has some hidden gems. It is fair to say that InDesign does not write a very good ebook CSS file. It exports too much information, including things that will definitely interfere with accessibility.
For example, the InDesign generated CSS will define the text as black, which will mean that most text will not invert when a user switches to night mode. Defining the body font size as 0.917em — which is often what 12-point type turns into — means that a user with low vision may not be able to upsize the font in some reading systems. Some of the CSS is nonsense that no reading system will respect, and some of it is repetitive and unnecessary — like text-transform:none. Twenty lines of CSS definitions can be condensed down to eight lines. With a really good CSS, it could be compressed even further.
InDesign’s CSS is not only overburdened but can actually get in the way of accessibility. We encourage you to develop your own CSS, or crib from others. Blitz.css is a very good starting place. While no longer under active development, Blitz CSS is still a very usable, excellent ebook CSS resource. Please consider starting there and swapping in that set of CSS definitions for the overwrought CSS that InDesign will produce for you. To do that, uncheck Generate CSS in this window, and ask ID to embed a CSS that you add here in the Additional CSS window. The ability to change the font size and font are foundational to accessibility so don’t let InDesign’s CSS to undo the good work you’ve done to make an accessible EPUB.
The final window is the metadata window — and it is already populated with the details that you may have put into the File —> File Info window. You might add an ISBN identifier here, and a publisher to round out this data.