Semantic HTML

You might say

The SEO check says my page is missing an H1. What does that mean?

HTML tags that mark each section's role in the document, such as headings, lists, and navigationWhen structuring a web page, semantic HTML tags indicate the structural role of each piece of content, such as H1 for the main heading, nav for navigation, and ul for lists. While enlarging text with CSS changes its visual weight, screen readers and search engines rely on tags to understand relationships. A page usually has one H1, and headings should descend in sequence without skipping levels.

Know first

HTML

Semantic HTML

A page's heading levels: click a section to see its tag

example.com

The page's main heading: usually only one per page

The outline is read by tags, not by font size
Levels descend: H1 → H2 → H3, no skipped levels

Biggest font size does not mean highest level: heading tags express structure, visual size is only styling.

Why heading levels have an order

One H1 per page: H1 marks the role of the page's main heading; multiple H1s make the outline lose its single entry point.

Levels descend in order: H1→H2→H3 expresses hierarchy; jumping from H1 straight to H3 breaks the structure.

Machines and people read it: Screen readers jump through headings, SEO understands content by outline; font size only affects appearance.

Quick checkChoose the best answer

A page has two H1s, and subsections jump from H1 straight to H3. What is structurally wrong?

A page usually has one H1, and levels should descend H1→H2→H3; skipping breaks the outlineAs long as font sizes look right, any tag worksUse H1 on whatever text has the largest font size

You can say this to an AI Agent

Check this page's heading structure: there should be only one H1 as the main heading, with subsections descending in H2, H3 order and no skipped levels. Afterward, confirm the order with an outline view or checker and tell me the heading text at each level.

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