Glossary

H3 Tag

The third-level HTML heading used to mark subsections within an H2 section.

Definition

The H3 tag is an HTML heading element — written as <h3>Subsection Title</h3> — used to mark subsections within an H2 section. H3 headings create a third level of hierarchy on a page, breaking H2 sections into finer sub-points. They are commonly used in step-by-step guides, FAQ sections, and detailed tutorials where each major section has multiple distinct subtopics.

Why It Matters

H3 headings add another layer of scannability and structure to complex content. For long-form content like ultimate guides or comprehensive tutorials, H3s help readers navigate directly to the specific information they need. Google can extract H3-level content for featured snippets and use the heading hierarchy to understand a page's full content architecture.

Examples

H3 under an H2H2: 'How to Write a Meta Description' → H3: 'Length Guidelines' → H3: 'Including Keywords' → H3: 'Writing for CTR'

FAQ H3sH2: 'Frequently Asked Questions' → H3: 'What is keyword density?' → H3: 'How do I check keyword density?'

Common Mistakes

Using H3 when there is no parent H2 — always maintain proper heading hierarchy.

Creating H3 headings for content that is better presented as bullet points.

Writing H3 labels that are so brief they provide no meaningful information to scanners.

Nesting H4 and H5 tags beyond what content complexity actually warrants.

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Related Terms

H2 Tag

The second-level HTML heading used to mark major sections within a page.

H1 Tag

The main HTML heading tag that marks the primary title of a web page.

Subheading

A secondary heading used to organize sections within a piece of content.

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