#1216: WG Revision: EPUB 3.4

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Opened Apr 2, 2026

Specification

https://www.w3.org/TR/epub-34/

Explainer

https://w3c.github.io/epub-specs/epub34/overview/

Links

The specification

Where and by whom is the work is being done?

  • GitHub repo: https://github.com/w3c/epub-specs/
  • Primary contacts:
    • Toshiaki Koike (@toshiakikoike), Voyager Japan
    • Wendy Reid (@reidmore-online), W3C Invited Expert
    • Brady Duga (@bduga), W3C Invited Expert
    • Gautier Chomel (@gautierchomel), EDRLab
  • Organization/project driving the specification: W3C EPUB Working Group

Feedback so far

EPUB 3.3 was previously reviewed and signed off by the TAG in #684 and #816. This new version, EPUB 3.4, is a maintenance update. Key changes based on previous feedback and WG consensus:

  • Simplification:
    • We removed several under-utilized attributes (primarily related to layout) that were often ignored by Reading Systems to better align with actual user-controlled experiences.
    • Dropped font obfuscation, which had been criticized in previous reviews.
  • Architecture:
    • Emphasis on the layered security model: EPUB inherits security from W3C Web standards and leverages the security features of modern WebViews used in Reading Systems.

You should also know that...

Key new features include:

  • Roll Layout: Introduction of roll layout support, enabling "Webtoons" and similar vertical-scroll content within EPUB.
  • Annotation Exchange: Support for exchanging annotations between Reading Systems (Note: This specific feature is currently in First Public Working Draft and will be subject to a separate, more detailed TAG review later).

Other improvements:

  • Accessibility and Standards: Further refinements for accessibility and improved alignment with modern Web Platform standards.

We have prioritized backward compatibility and ensured there are no breaking changes to the Web architecture.

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Track conversations at https://tag-github-bot.w3.org/gh/w3ctag/design-reviews/1216

Discussions

Discussed Apr 6, 2026 (See Github)

Mattthew: I can do as many APA people are already involved in it.

JEffrey: I think APA should do that, it might include some security items that can relate to architecture but not sure yet.

Matthew: I wonder if there has been many changes to that?

Heather: It says there are some changes

Matthew: I found it. thanks.

Jeffrey: I suggest we decline it and refer to APA as appropriate review target. We can say we see no architeture issues with it. Here is my draft comment:

Draft comment:

Thank you for sending us this review. We don't see any likely architectural implications from the changes you've summarized, so we're going to decline to do a detailed review. We think the other horizontal groups will cover the topics they focus on.

then close the review.

Comment by @jyasskin Apr 10, 2026 (See Github)

Thank you for sending us this review. We don't see any likely architectural implications from the changes you've summarized, so we're going to decline to do a detailed review. We think the other horizontal groups will cover the topics they focus on.