A Chart of the Differences between ePub2 and Accessible ePub3

A Chart of the Differences between ePub2 and Accessible ePub3

While the two formats may appear similar or identical to a user when they are viewed in a reading app, the significant differences listed below will appear when the reading app is equipped to display accessibility features. The Thorium Reader is recommended for this reason.

Another way to view/evaluate Accessibility features in the Accessible ePub3 is to use the ACE Report. 

Feature

EPUB 2

Accessible EPUB 3

Publication Format

XHTML 1.1

XHTML5 and HTML5

Media Support

Limited to text and static images

Supports audio, video, and interactive elements like JavaScript

Text Layout

Reflowable text only

Supports both reflowable and fixed-layout formats

CSS

CSS2

CSS3

Metadata

Basic Dublin Core metadata

Expanded metadata, including EPUB 3-specific metadata properties

Navigation

Table of Contents (TOC) only

Advanced navigation with multiple navigation documents, landmarks, and page lists

Media Overlays

Not supported

Supports synchronized media overlays (text and audio synchronization)

MathML

Not supported

Full support for MathML for mathematical and scientific content

SVG

Limited support

Full support for SVG, including standalone SVG documents

Scripting

Limited JavaScript support

Enhanced scripting support using HTML5 and JavaScript

Font Embedding

Supported

Improved support for font embedding and CSS3 fonts

Annotations

Not supported

Basic annotation support

Accessibility

Basic accessibility with alt text

Enhanced accessibility with ARIA roles, improved semantic structure, and better media overlays support

Package Document

OCF (Open Container Format) with OPF 2.0

OCF with OPF 3.0, allowing greater flexibility and richer content descriptions

Content Documents

EPUB Content Documents

Expanded to include EPUB Publications, enabling richer, more interactive content

Interactive Features

Limited

Enhanced interactive features using JavaScript, HTML5 forms, and CSS animations

Linking

Basic linking within the document

Advanced linking, including fragment identifiers and linking to specific locations within resources



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