Semantic HTML checker for AI search

Semantic HTML is the structure AI search engines read your page through. Clean markup tells them what your topic is and where each section starts. This checker tests the basics everything else depends on.

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5 checks · 6% of the Slurp Score · Updated July 2026

Why semantic HTML matters for AI search

Your H1 declares the topic of the page. Your heading order tells retrieval systems where to split it into chunks. Landmarks separate real content from navigation, and the lang attribute decides which language index you belong in. None of this is advanced, which is what makes a failure here expensive.

The stakes went up when agents arrived. Crawlers parse your structure into an index, and browsing agents like ChatGPT-User now operate live pages for people. An agent that cannot tell your content from your navigation finishes the task badly, and your visitor blames your site.

Studies and sources: HTML specification: sections and headings

What GetSlurp checks

  • Single H1 One clear topic declaration per page.
  • Heading order A sequential outline with no skipped levels.
  • Landmarks main and nav elements separating content from chrome.
  • Language A lang attribute that puts you in the right index.
  • Link text Descriptive anchors instead of "click here".

Every check in this category

This list comes straight from the audit engine, so it always matches what the extension and MCP server actually run.

semantic.single-h1Graded

The H1 is the strongest single statement of what a page is about; zero or multiple H1s blur the topic for extraction.

Fix: Use exactly one H1 that states the page topic.

semantic.heading-orderGraded

Skipped heading levels break the outline that retrieval systems use to segment the page.

Fix: Do not skip heading levels (H2 to H4); keep the outline sequential.

semantic.landmarksGraded

Landmark elements (main, nav) tell parsers and browsing agents which part of the page is content versus chrome.

Fix: Wrap the primary content in <main> and navigation in <nav>.

semantic.langGraded

The lang attribute tells engines which language index and answers the page belongs in.

Fix: Set lang on the html element (e.g. <html lang="en">).

semantic.link-textGraded

Descriptive anchors tell machines what the target is; "click here" carries zero information.

Fix: Rewrite generic anchors ("click here", "read more") to describe their destination.

Semantic HTML checker for AI search: frequently asked questions

Why does semantic HTML matter for AI?

Crawlers parse your markup into chunks for retrieval, and browsing agents operate the live page. One H1, a logical heading outline, landmarks and a lang attribute tell them what your content is and where it starts.

How many H1 tags should a page have?

One. The H1 declares the page topic. Multiple H1s or a broken heading order make it harder for engines to split your page into clean, citable sections.

Is semantic HTML different for AI than for SEO?

The markup is the same, but the stakes are higher. Both crawlers and live browsing agents rely on structure, and an agent that cannot tell content from navigation completes tasks badly for your visitors.

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