Heading levels must not skip

PDF/UA check HEADER_NESTING · Headings · severity High · PDF/UA 8.2.5.12 Headings

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Why it matters#

Jumping from H1 to H3 skips a level, confusing users who navigate by headings. Proper nesting (H1 → H2 → H3) creates a logical outline that users can follow.

What you will see#

The heading sequence jumps a level — for example an H1 followed directly by an H3.

How to fix#

Renumber the heading tags so levels descend one step at a time (H1 then H2 then H3) without skipping. For example, retag an H3 that directly follows an H1 as H2, or confirm the skipped level reflects the document's intended structure.

Step-by-step guide#

1. List all heading tags in document order (EQChecker report or the Accessibility tags panel) and note each place a level is skipped, e.g. an H1 followed directly by an H3.
2. Decide the correct level for each flagged heading from its role in the content: a direct subsection of an H1 section is H2, not H3.
3. Retag it: select the heading in the Accessibility tags panel and change Properties > Type, or use All tools > Prepare for accessibility > Fix reading order (the Reading Order tool), select the heading content on the page, and click the correct heading button.
4. Re-check subsequent headings after each change - renumbering one heading often shifts what the following levels should be.
5. If a skip genuinely reflects the intended document structure, you may leave it: PDF/UA-2 requires only that each heading's tag match its evident level, not that levels be sequential.

Verify: Re-run the EQChecker scan: HEADER_NESTING warnings should clear. Acrobat's accessibility check (All tools > Prepare for accessibility > Check for accessibility) should pass Appropriate nesting under Headings.

Note: Best-practice warning only: ISO 14289-2 8.2.5.12 NOTE 2 explicitly declines to require sequential heading levels (unlike PDF/UA-1), and no WCAG success criterion requires them. Content inside a DocumentFragment may legitimately keep the heading levels of its source document (8.2.5.2 NOTE 3). Validators running in PDF/UA-1 mode do fail skipped levels, so fixing them also helps dual-standard files.

WCAG success criteria#

1.3.1 Info and Relationships — Level A#

Structure and relationships conveyed visually (headings, lists, tables, labels, groups) must also be available programmatically.

Understanding 1.3.1

Standards#

This check contributes to the following standards:

PDF/UA WCAG A EN 301 549