Warning Heading structure — missing, duplicate, or skipped levels
Why pages need one clear H1 and a logical H1→H2→H3 order, and how screen reader users navigate by heading level.
The validator checks three things: whether the page has no <h1> at all (missing-h1, warning), whether it has more than one (multiple-h1, informational), and whether heading levels jump — for example H2 straight to H4 (heading-skip, warning).
Example
<!-- Wrong: skips H2 -->
<h1>Article title</h1>
<h3>Subsection</h3>
<!-- Right -->
<h1>Article title</h1>
<h2>Section</h2>
<h3>Subsection</h3>Why it matters
Screen reader users commonly navigate a page by jumping between headings — most screen readers have a dedicated shortcut that pops up a list of all headings, letting the user scan a page's structure the way a sighted user scans visually with font sizes. A skipped level (H2 to H4) makes that outline confusing, implying a level of nesting that doesn't actually exist in the content. A missing H1 means there's no clear top-level topic; multiple H1s are technically valid in HTML5's outline model (each can represent a new sectioning root) but are worth double-checking — most pages read more clearly with exactly one.
Frequently asked questions
Can a page ever have more than one H1?
Yes — HTML5's sectioning model permits multiple H1s, for example one per <article> on a page listing several articles. It's flagged as informational, not an error, precisely because it's sometimes intentional. For a single-topic page, though, one H1 makes the structure clearest.
Is heading order about visual size or document structure?
Structure, not size. Headings can be styled to any font size with CSS — what matters for accessibility and SEO is that the levels (H1, H2, H3...) reflect the actual nesting of topics and subtopics, independent of how large they render.