ONPAGE · SEO GLOSSARY
Heading Tags (H1–H6)
HTML elements that define the hierarchical structure of page content — H1 for the page title, H2 for main sections, H3 for subsections — used by Google to understand content organisation and topic coverage.
Definition
Heading tags are HTML elements (`<h1>` through `<h6>`) that define the semantic hierarchy of a page's content. In SEO, H1–H3 are the most significant: (1) **H1** — the page's primary heading. There should be exactly one H1 per page, and it should describe the page's main topic clearly. Google uses the H1 as a strong signal of what the page is about — it should include the target keyword and align closely with the title tag. (2) **H2** — section headings that divide the page's content into major topics. Each H2 should address a distinct subtopic or angle of the main query. H2s that are phrased as questions (covering People-Also-Ask variants) can help a page rank for related queries. (3) **H3** — subsection headings under each H2 section. Used for further detail, step lists, or FAQ items. H3 FAQ items with `FAQPage` JSON-LD schema are eligible for rich result display in the SERP.
Why it matters for SEO
Heading structure serves both SEO and user experience. For SEO: Google's algorithms use heading text to understand page structure, topic coverage, and entity relationships — a well-structured H1→H2→H3 hierarchy tells Google what the page is about and what subtopics it covers. For users: headings make long pages scannable — users can jump to the section they need rather than reading linearly. Pages with no headings, a single long H2 list, or headings that don't reflect the page's actual content score poorly on both SEO and usability. The AI visibility score checks that ≥20% of H2/H3s are phrased as questions — question headings improve eligibility for featured snippets, voice search answers, and AI citation.
How DeepSEOAnalysis checks this
The audit checks: H1 presence (flagged as critical if missing), H1 uniqueness across all crawled pages (duplicate H1s = likely duplicate content), H1 length and keyword presence, heading hierarchy (H3 appearing before an H2 is a structure error), question-heading ratio for AI visibility (% of H2/H3s starting with interrogative words: How, What, Why, When, Where, Who, Is, Are, Does, Can), and heading count vs. content length (very long pages with only 2–3 headings may have poor content structure).
Useful tools and resources
GLOSSARY
Related terms
onpage
On-Page SEO
Optimising the content and HTML elements of an individual page — title tag, meta description, headings, body copy, images, and internal links — to rank for its target query.
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Title Tag
The HTML <title> element that names a page in browser tabs, SERP snippets, and social shares — the single most important on-page SEO element.
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Featured Snippet
A special SERP result that displays a direct answer pulled from a webpage above the standard organic listings — also called "position zero."
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SEO Copywriting
Writing page content that satisfies both search engine ranking signals (keyword relevance, structure, depth) and human readers (clarity, persuasion, and genuine usefulness).
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Structured Data
Machine-readable annotations added to HTML — usually JSON-LD — that explicitly describe what a page is about to search engines and AI systems.
Read definition →See how your site scores on Heading Tags (H1–H6).
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