Skippable and Escapable Elements in EPUB 3

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Skippable and Escapable Elements in EPUB 3

photo of a hurdle on a running trackIntroduction

At Dedicon, we strive to make information accessible to people with reading disabilities. Our roadmap aims to deliver a personalized, multi-modal reading experience to all of our customers. We expect that EPUB (version 3) will form the cornerstone of our future products, so over the last three years we have been exploring the features of EPUB as the go-to standard for inclusive publishing[1].

This article discusses two features in particular: skippability and escapability. We highlight their importance for the reading experience of people with a reading disability, but must conclude that these features are not widely supported at this time. We therefore want to engage developers in adding support for these features to their reading systems, and to gather information from other content providers about the alternatives they employ while support in reading systems is missing.

Customer needs and wishes are changing. There is a shift from standardized to personalized content. For example, someone could read large print in the morning and switch to human voice audio in the evening when reading print becomes too much of a strain. Or someone could listen to the audio version of a book, while preferring to see enlarged images rather than listening to image descriptions. EPUB allows us to build the rich, multi-modal products in which users can freely choose how they want to read. However, when synchronized audio is included or when a read-aloud function is available, we believe that skippability and escapability are features that are essential to offer the user. These features ensure that users receive the information they need without being overwhelmed by information that is irrelevant to them. This is increasingly important as publications become more complex.

Skippability and escapability

The W3C defines skippable and escapable elements as part of the EPUB Media Overlays specification, which also contains examples. An element is skippable if it can be excluded from being read. For example, sometimes you want to ignore secondary content such as footnotes or page breaks. Skippability is also useful for content alternatives that cater to a specific audience, such as image descriptions.

An element is escapable if it can be jumped out of at any point while being read. For example, you may want to stop reading a longer piece of content such as a table before reaching the end. Finally, an element can be both skippable and escapable, meaning that you can turn it on or off as well as jump out of it halfway through.

Skippability and escapability can also be applied to the read-aloud feature of a reading system, the only significant difference being that speech is synthesized instead of pre-recorded. Control of the (synthesized) audio playback remains the responsibility of the reading system. This is different from accessing the text of a publication using a screen reader. A typical screen reader offers many options for customizing its output, including features like skippability and escapability. However, not everyone who could benefit from these features will use a screen reader. People with dyslexia are much more likely to take advantage of a read-aloud function.

The state-of-the-art in reading systems

During 2018 through early 2020, we investigated the state-of-the-art of multi-modal reading in accessible EPUB (version 3) reading systems, both hardware and software. These tests did not reveal a reading system that supports skippability and escapability in media overlays. In fact, support for media overlays in general was often not available. For many reading systems, this would be a fundamental step towards multi-modal reading. For now, the limitations we encountered mean that we must strike a balance between delivering all the rich content we have to offer and giving customers too much content to listen to.

Read-aloud features of reading systems perform a bit better. For example, in the read-aloud feature of VitalSource Bookshelf it is possible to enable or disable reading of text alternatives for images. This is a promising starting point, because as the world becomes more and more visual, image descriptions should become an integral part of many accessible publications. Being able to turn them on and off aids the personalized reading experience, but is no longer sufficient when descriptions become longer, necessitating escapability as well. It would also be good to see support for other elements besides images, such as notes and page numbers.

Exploring the alternatives

Coming back to the compromise resulting from the limitations of reading systems, we could also try to remedy the situation in our content. The key requirement here remains the same: the publication must be suitable for a broad variety of users. The only feasible solution that we found is to use scripting technologies, such as JavaScript, to allow the user to toggle features on and off within the content itself. Besides the question of how to store the state of the EPUB between reading sessions, this could be a good solution to implement skippability. Escapability is a different problem, though, because the reading system controls the playback and scripting cannot influence this. Another option is to use another content format, but this imposes limits on other functionality, such as interactivity. We would like to invite other content producers to share their experiences in this area.


Skippable and escapable elements are important for a personalized, uncluttered reading experience. They allow the user to skip or pass over elements of a book, but also allow the content provider to include additional content without the user having to read all of it. Skippable and escapable elements are not widely supported yet, although in theory our content is ready for it, provided that the reading system is designed to support these functionalities. We would like to urge developers to invest in these features, but are also eager to learn about alternative strategies from other content providers.

Authors: Davy Kager (Product manager) and Vincent de Jong (Project manager)

Dedicon, The Netherlands

[1] The exploration of accessibility features as well as testing other state-of-the-art EPUB features in reading systems was part of a project which was made possible through funding from the National Library of The Netherlands.