Back to Error DirectoryW3C EPUB Accessibility 1.1 & European Accessibility Act
ACC-001Retailer Warning

Skipped Heading Levels Violating WCAG 2.1 AA

Heading structure skips levels (e.g. <h1> directly to <h3> without an <h2>).

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PreFlight audits the DOM heading tree across all chapters, flags hierarchy skips, and normalizes semantic heading elements to ensure WCAG 2.1 AA compliance.

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What This Error Means in Plain English

For blind readers using screen readers, headings serve as an auditory table of contents. If you jump from a Title (H1) straight to a sub-section (H3) without an H2, screen readers report broken document structure.

Why Retailers & EAA Regulations Block This File

Mandated under WCAG 2.1 AA Success Criterion 1.3.1 (Info and Relationships) enforced by the European Accessibility Act.

Technical Specification: Heading elements must strictly follow sequential nesting: h1 -> h2 -> h3 -> h4. Skipping levels breaks assistive technology outline parsing.

Manual Fix Instructions (for Sigil / Calibre)

  1. Open your chapter files and review all <h1-h6> tags.
  2. Ensure proper sequential hierarchy is maintained, using CSS styling classes rather than jumping heading levels for visual sizing.