What is EPUB Accessibility 1.1?

EPUB Accessibility 1.1 is a standard from the W3C/IDPF that defines accessibility requirements for EPUBs. It incorporates WCAG 2.2 by reference and adds EPUB-specific requirements: logical reading order, navigation document, and accessibility metadata in the OPF. Conformance levels are AA (minimum), AAA, and Optimized.

Which WCAG success criteria apply to EPUBs?

Key WCAG 2.2 AA criteria for EPUBs include: 1.1.1 (alt text for images), 1.3.1 (semantic structure), 1.3.2 (reading order), 1.4.3 (contrast 4.5:1), 1.4.4 (text resize), 2.4.2 (page titles), 3.1.1 (language declared), and 4.1.1 (valid markup). EPUBCheck validates markup; Ace by DAISY checks accessibility criteria.

How do I test an EPUB for accessibility?

Use two tools: EPUBCheck (java -jar epubcheck.jar book.epub) for spec validation, and Ace by DAISY (ace book.epub -o report/) for WCAG accessibility checking. Ace generates an HTML report with violations, warnings, and best-practice notices. Supplement with manual testing using NVDA+Firefox on Windows or VoiceOver+Safari on macOS.

What accessibility metadata is required in an EPUB?

EPUB Accessibility 1.1 requires in the OPF: schema:accessMode, schema:accessModeSufficient, schema:accessibilityFeature, schema:accessibilityHazard, schema:accessibilitySummary, a11y:certifiedBy, and dcterms:conformsTo (with the conformance level). Without this metadata, the EPUB does not conform even if the content is technically accessible.

What are the most common accessibility failures in converted EPUBs?

Most common: images without alt text (especially charts and figures), tables lacking th header cells, html element missing xml:lang, content files with no title element, skipped heading levels (H1 to H3 without H2), and links with vague text like 'click here'. Run Ace by DAISY to catch these automatically.

EPUB Accessibility and WCAG 2.2: A Practical Compliance Guide

June 12, 2026 · 8 min read

EPUB Accessibility 1.1 is built on WCAG 2.2 AA. Meeting it requires both structural EPUB requirements and specific WCAG success criteria. This guide maps the key requirements to concrete implementation steps.

EPUB Accessibility 1.1 vs WCAG 2.2

EPUB Accessibility 1.1 is an EPUB-specific accessibility standard that incorporates WCAG 2.2 by reference. An EPUB can conform to three levels:

EPUB Accessibility 1.1 (WCAG AA) — minimum conformance; meets WCAG 2.2 Level AA
EPUB Accessibility 1.1 (WCAG AAA) — meets WCAG 2.2 Level AAA
EPUB Accessibility 1.1 Optimized — AA plus additional optimisations (page list, extended descriptions)

Key WCAG Success Criteria for EPUBs

SC	Requirement	EPUB implementation
1.1.1	Non-text content has alt text	alt attribute on all img elements; empty alt for decorative
1.3.1	Info and relationships conveyed in structure	Semantic HTML: h1-h6, ul/ol, table with thead/th, figure
1.3.2	Meaningful sequence	Document order matches reading order; no CSS-only reordering
1.4.3	Contrast ratio 4.5:1 (text)	Minimum contrast in embedded CSS; test with Colour Contrast Analyser
1.4.4	Text resizable to 200% without loss	Use em/rem units; avoid px for font-size
2.4.1	Skip navigation blocks	TOC allows skipping to content; landmarks nav in nav.xhtml
2.4.2	Page titled	title element in each XHTML head
2.4.6	Headings and labels descriptive	Meaningful heading text, not just "Chapter 1"
3.1.1	Language of page	xml:lang on html element in each XHTML file
4.1.1	Parsing — valid markup	Pass EPUBCheck and W3C XHTML validator
4.1.2	Name, role, value for UI	ARIA roles where semantic HTML is insufficient

Required EPUB-Specific Requirements

Beyond WCAG, EPUB Accessibility 1.1 adds these EPUB-specific requirements:

Logical reading order — spine order must match the intended reading sequence
Navigation — EPUB 3 NAV document required; TOC must cover all major sections
Accessibility metadata — schema:accessMode, schema:accessibilityFeature, schema:accessibilitySummary, and a11y:certifiedBy in OPF

<!-- Required accessibility metadata in content.opf -->
<meta property="schema:accessMode">textual</meta>
<meta property="schema:accessMode">visual</meta>
<meta property="schema:accessModeSufficient">textual</meta>
<meta property="schema:accessibilityFeature">structuralNavigation</meta>
<meta property="schema:accessibilityFeature">alternativeText</meta>
<meta property="schema:accessibilityFeature">tableOfContents</meta>
<meta property="schema:accessibilityHazard">none</meta>
<meta property="schema:accessibilitySummary">
  This publication includes structured navigation, alt text for all
  informative images, and semantic heading structure.
</meta>
<meta property="a11y:certifiedBy">Your Organisation</meta>
<meta property="dcterms:conformsTo">
  EPUB Accessibility 1.1 - WCAG 2.2 Level AA
</meta>

Testing Tools

EPUBCheck — validates EPUB spec conformance (not accessibility): java -jar epubcheck.jar book.epub
Ace by DAISY — WCAG accessibility checker for EPUBs: ace book.epub -o ace-report/. Generates HTML report with violations, warnings, and best practice notices.
NVDA + Firefox — manual screen reader test on Windows (free)
VoiceOver + Safari — manual test on macOS/iOS (built-in)
Colour Contrast Analyser — check text/background contrast ratios against 4.5:1 threshold

Common Accessibility Failures in Converted EPUBs

Images without alt text (especially charts and figures from PDF)
Tables without <th> header cells or scope attributes
Language not declared on <html> element
No page title in <title> element
Heading hierarchy skipped (H1 → H3, missing H2)
Links with non-descriptive text ("click here", "read more")

Accessible PDF-to-EPUB Conversion

toolkit.bot outputs EPUBs that target EPUB Accessibility 1.1 at WCAG 2.2 AA conformance. Alt text is generated for images, semantic heading structure is preserved from the PDF, language is detected and set, and accessibility metadata is included in the OPF. Run Ace by DAISY on the output to verify before distribution.

Convert PDF to accessible EPUB3 →