Heading hierarchy

lowseo-heading-hierarchy

Headings should step down one level at a time. Skipping from h2 to h4 breaks the outline screen readers and search engines both rely on.

What it is

Heading hierarchy is whether a page's <h1> through <h6> tags step down one level at a time — an <h2> can be followed by another <h2> or an <h3>, but not by an <h4> with no <h3> in between. This check reads the sequence of heading tags in the order they appear in the HTML.

It's independent of the separate missing-H1 and multiple-H1 checks: a page can have exactly one H1 and still skip a level further down the outline.

Why it matters

Screen reader users commonly navigate a page by jumping between headings rather than reading linearly, and a skipped level makes that outline misleading — landing on an H4 with no H3 context reads as a subsection of nothing.

It's a low-severity, easy-to-audit signal rather than a functional break, which is exactly why it's worth fixing while a codebase is small: an inconsistent heading structure tends to compound as more sections get added by more people.

How to fix it

with a reference doc
html
<h1>Page title</h1>
  <h2>Section</h2>
    <h3>Subsection</h3>
  <h2>Next section</h2>

Reference documentation

Related checks

3
highMissing title tagThe <title> tag in a page's <head> names the page for browsers, search results and social shares. It's one of the few pieces of a page search engines still treat as an explicit, author-declared signal rather than something inferred from content.mediumImage alt textEvery <img> should carry an alt attribute: a text description for informative images, or an empty alt="" for images that are purely decorative. This check reads it directly out of the HTML the server sent, so it runs on every scan regardless of whether a rendering engine is available.highColor contrastThis reads Lighthouse's own color-contrast audit: whether text has enough contrast against its background, judged by the WCAG formula rather than eyeballed. The threshold is 4.5:1 for normal text and 3:1 for large text (18pt+, or 14pt+ bold).

This is one of the 75 checks the scanner runs. See what we check for the full list, every severity weight, and how the score is computed from them.

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