Quick answer
The single-h1 check passes when NOTABIS measures exactly one H1 element in a page’s HTML. It is a structural measurement, not a guarantee that the heading is visible, descriptive, or the best title for the page. A page with zero or multiple H1s is covered by the separate missing or multiple H1 findings.
What the issue means
An H1 normally identifies the page’s primary subject. A useful structure might be:
<h1>Women’s trail running shoes</h1>
<h2>Fit and sizing</h2>
Counting one H1 does not tell you whether it names the page, appears in the main content, or is duplicated elsewhere as hidden template output. CSS and client-side rendering can also make the visual experience differ from the initial markup.
Why it matters for SEO
A clear main heading helps readers orient themselves and gives search systems another piece of page context. Google does not require exactly one H1 as a ranking rule, and a passed count does not guarantee visibility or indexing. Review the heading alongside the title, page text, and template structure.
How NOTABIS detects it
The single-h1 rule is a page-level passed check created when the measured HTML contains exactly one h1 element. NOTABIS counts elements and does not evaluate wording, CSS visibility, prominence, accessibility names, or headings added after the initial response. The check therefore confirms a count only.
How to check it yourself
Inspect the DOM and View Source for h1, then read the heading in context. Check responsive layouts, dialogs, duplicate components, and JavaScript route transitions. Confirm that the visible heading describes the page’s subject and that lower-level headings form a sensible outline.
How to fix it
If a page has one H1 but the wording is vague, rewrite it to describe the page rather than changing the count. Keep the element in the primary content region and use H2 and H3 for nested sections. For a client-rendered site, server-render the SEO-critical heading when the initial response needs to expose it. Recheck title and anchor styling after template changes.
When this is intentional or does not need fixing
Utility responses, redirects, and private application views may not need a content H1. A component system may use more than one H1 in a valid experience; inspect the multiple H1 guidance before rewriting it solely to satisfy a counter. The goal is understandable content structure, not a magic number.
Related issues
Compare missing H1 tags, multiple H1 tags, and skipped heading levels.
Run a NOTABIS audit
The NOTABIS evidence view shows when a page passed the exact-one-H1 check and lets you inspect the measured heading markup.