EPUB Accessibility

EPUB Accessibility 1.1 is the W3C Recommendation (also published as ISO/IEC 23761:2021) that defines what makes an EPUB digital publication accessible. It’s the operative standard for e-book accessibility across all major reading systems — Apple Books, Google Play Books, Kindle (via KFX/Calibre conversion), Adobe Digital Editions, Thorium Reader.

The European Accessibility Act explicitly puts e-books in scope; for any EPUB sold in the EU after 28 June 2025, EPUB Accessibility 1.1 is the implicit conformance target.

The two pillars

EPUB Accessibility splits into two requirement sets:

1. Discovery metadata. Every EPUB must declare its accessibility characteristics through Schema.org-based metadata in the package document: accessibilityFeature (alternative text, captions, long-description, MathML), accessibilityHazard (none, flashing, motion-simulation), accessibilitySummary (a plain-language description), and accessMode / accessModeSufficient (text, visual, auditory).

   This metadata flows through to retailer catalogs and library systems, letting users with disabilities filter for books they can actually use before purchasing.

2. Content conformance. The publication itself must conform to WCAG 2.x Level AA for the textual and structural content. EPUB inherits HTML’s accessibility model — headings, alt text, ARIA, table semantics, contrast — and adds EPUB-specific requirements around navigation document quality, page-list synchronisation, and the media-overlay specification for read-aloud audio.

Conformance levels

EPUB Accessibility 1.1 defines two conformance levels:

• WCAG 2.x Level AA — the practical floor, equivalent to the WCAG conformance level required by EAA / EN 301 549 for web content.
• WCAG 2.x Level AAA — used by select educational and library imprints aiming for the highest accessibility level.

Both levels require the metadata declarations regardless of which content conformance level is claimed.

How to test EPUB accessibility

The widely-adopted tool is Ace by DAISY — an open-source checker from the DAISY Consortium that runs WCAG-aware checks adapted to EPUB structure, validates the required metadata, and produces a conformance report. Like PAC for PDFs, Ace catches the automatable issues; manual review is still required for alt-text quality, reading-order coherence across complex layouts, and rendering checks across multiple reading systems.

Why this matters beyond compliance

The discovery metadata pillar matters more than the EAA legal angle alone suggests. The Accessible Books Consortium and the Marrakesh Treaty have built a global library exchange for accessible-format books. EPUB Accessibility metadata is what makes a book findable in those systems. Publishers who treat EPUB accessibility as a checkbox exercise — declaring “yes accessible” without doing the metadata work — end up invisible to the user populations they’re claiming to serve.