Legibility and Text Adjustment in Ebooks
Written by
Monika Zarczuk-Engelsma
Posted on
May 7, 2025
Category
Accessibility
Ensuring Legibility and Text Adjustment Options in Ebooks
Text adjustment in ebooks is one of the key aspects of accessibility, but its effectiveness depends on many factors, like the way the file is prepared, technical limitations of ebook readers and good practices in designing content. Editors, programmers and ebook creators should aim to make digital books as flexible and adjusted to users’ individual needs as possible.
Modern formats, especially EPUB, offer functions like regulating font size, changing background colours or choosing a typeface. Unfortunately, in reality it is not always possible for users to fully access these adjustments.
Why? Let’s analyse the most frequent challenges and the best practices in this area.
EPUB and Reflow – Flexibility: Theory and Practice
The EPUB format is one of the most popular standards for digital publications. One of the reasons for that is that it works with reflow – a mechanism which enables the adjustment of text layout to different screens and the user’s preferences. In theory, it means that the reader can:
enlarge or reduce font size without losing legibility,
adjust background and text colours to their needs (e.g. night mode),
• use different fonts, including those designed for people with dyslexia.
Unfortunately, this flexibility does not always function perfectly. Limitations may be caused by editors’ decisions or differences in how formats work on a given app or reader.
Obstacles in Content Adjustment
Although EPUB offers advanced adjustment options, some editorial and technological decisions can lead to limiting of users’ comfort. Some of them are:
1. Too rigid CSS styling
EPUB uses CSS to format text, which offers many possibilities but also causes some problems. One of the most frequent mistakes is setting font sizes in pixels rather than in flexible units (e.g. em, rem). Because of this, text is not scaled correctly and users lose control over its size.
Using forced page layouts, like columns or blocks of text, is another problem, as they do not react well to users’ changes of settings. This might make an ebook less functional, especially on small screens.
2. Problems with reader compatibility
Each ebook reader app interprets the EPUB format differently. For example:
Kindle – officially works with EPUB but converts it to its own format (KFX), which might limit some functions.
Apple Books – offers a wide range of adjustment possibilities, but not all fonts rooted by the editor are always displayed correctly.
Adobe Digital Editions – although it is a popular choice in digital libraries, its possibilities of personalising text layout are limited.
Some readers do not work with rooted fonts, which means that the user does not always have the possibility to use optimised typefaces, e.g. for people with dyslexia.
3. Problems with non-text content
Infographics, graphs or text scans saved as images are another challenge. These elements are not scaled along with text and might become illegible when zoomed in. People who use screen readers face one more problem – the lack of alternative descriptions of graphics, which makes it impossible to fully understand the content.
Designing Accessible Ebooks – Good Practices
In order to make ebooks truly functional for all users, we provide a few tips worth following:
Using relative units (em, rem) instead of pixels – this enables smooth scaling of text.
Avoiding too rigid layouts – according to accessibility guidelines, the user should be able to change text size and layout freely.
Adding alternative descriptions to graphics – ensures accessibility for blind and visually impaired individuals. See: Making Images Speak: How to Write Alt Texts for Ebooks (https://blog.haveabook.eu/post/making-images-speak-how-to-write-alt-texts-for-ebooks).
Marking each document component (such as: text, headings, lists, graphics), which makes it possible for assistive tools to read them correctly. See: Semantic HTML: What it is and why it matters in ebooks (https://blog.haveabook.eu/post/semantic-html-what-it-is-and-why-it-matters-in-ebooks).
Making sure colours and contrast are chosen correctly, which will improve legibility for all readers, including those with vision disorders.
A correct Table of Contents, which makes navigation easier for people with disabilities. See: How Blind Individuals Navigate Ebooks: A User’s Experience (https://blog.haveabook.eu/post/how-blind-individuals-navigate-ebooks).
Using and including accessibility metadata, which enables users to quickly verify whether an ebook is adjusted to their needs. See: Metadata: The Key to Accessibility (https://blog.haveabook.eu/post/metadata-the-key-to-accessibility).
Supporting fonts adjusted to different needs, e.g. OpenDyslecxic for people with dyslexia, or legible seamless typefaces.
Testing ebooks on various readers to make sure formatting works correctly in different apps. File structure should enable logical navigation using a keyboard or any screen reader.
Remember that ebook accessibility is not only a matter of fulfilling standards or supporting people with disabilities – it is also a real profit for the publishing market at large. Well-prepared, well-ordered and accessible files are easier to browse and boost a publication’s quality. It is an investment which broadens a title’s range and opens it to a broader audience – regardless of their needs or ways of reading.
Bibliography:
https://www.accessibletextbooksforall.org/stories/creating-accessible-epub
https://www.ingramcontent.com/publishers-blog/fundamentals-of-ebook-accessibility
http://www.niepelnosprawni.pl/ledge/x/1963444;jsessionid=FFBB1FE4AADA116F1FCA595362423552
https://ef-ef.pl/2024/10/09/jak-dostosowac-e-booka-do-wspolczesnych-wymogow-dostepnosci/
The article was created in close collaboration between the Polish Foundation for the Blind and Visually Impaired "Trakt” and Have a Book.
Translated by Aleksandra Kallas