What this test checks
This test verifies that the PDF document contains a logical structure tree (StructTreeRoot). The structure tree organizes document content into headings, paragraphs, lists, tables, figures and other semantic elements that assistive technologies can navigate.
Why this maybe a barrier
A structure tree is one of the most important logical components of an accessible PDF. It represents the document's logical organization independently of its visual appearance and provides a semantic hierarchy for assistive technologies.
Without a structure tree, screen readers cannot reliably determine document structure, reading order, headings, lists, tables or form navigation. They must instead infer meaning from the page content stream, which often produces incorrect or confusing results.
WCAG 2.2 Success Criterion
1.3.1 Info and Relationships (Level A) — "Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text."
For more information, visit WCAG 2.2 Success Criteria 1.3.1, under the guideline Adaptable.
PDF/UA Principle
Section 7.1: General requires accessible PDF documents to provide a logical structure tree that represents the document's semantic organization. This structure enables assistive technologies to interpret the document correctly.