Semantic HTML Checker | HTML Structure Audit

Check semantic HTML structure for missing landmarks, skipped heading levels and div soup. Paste markup and get a scored, line-referenced report. Free. Designed specifically for developers and professionals, this free online analyzer runs entirely in your browser to process tasks quickly and securely. Enjoy unlimited usage with no data tracking and no registration required.

Also known as: semantic html checker · html structure analyzer online · heading order checker · html landmark checker · div soup detector · check heading hierarchy html · semantic markup validator · html accessibility structure check

html tools

seo tools

analyzers

HTML Input

Structure Report

The structure report will appear here, listing landmark, heading and markup findings by severity.

About Semantic HTML Checker

Semantic HTML Checker audits a page's structure rather than its syntax. Paste markup and it reports missing landmarks, headings that skip a level, images with no alt attribute, click handlers on div elements, and the ratio of plain wrappers to semantic elements. The result is a 0 to 100 score with one line per finding, so you can see what a screen reader or a search crawler would struggle with.

Key Features

Flags a missing or duplicated <main> and reports absent header, nav and footer landmarks
Detects heading levels that skip, such as an h2 followed directly by an h4
Counts h1 elements and warns when a page has none or more than one
Reports img elements with no alt attribute and gives the source line number
Catches onclick handlers on div and span, which keyboard users cannot reach
Scores the div and span count against real semantic elements to quantify div soup

Use Cases

Audit a marketing page before launch so crawlers can identify its main content region
Check a React or Next.js component's rendered output for heading order after a refactor
Review a third-party landing page template before adopting it for a .com property
Prepare an accessibility baseline ahead of a WCAG or Section 508 review
Teach a junior developer why a page of nested divs reads badly in a screen reader
Spot-check a CMS theme that emits its own wrappers around your content

Supported Formats

Full HTML documents

HTML fragments

Server-rendered markup

HTML5 landmark elements

Related Keywords

semantic html checker

html structure analyzer online

heading order checker

html landmark checker

div soup detector

check heading hierarchy html

semantic markup validator

html accessibility structure check

What counts as semantic HTML?

A semantic element describes what its content is, not how it looks. header, nav, main, article, section, aside, footer, figure and the heading elements all carry meaning that browsers, screen readers and search crawlers act on. A div and a span carry none, which is fine for layout but useless as structure. The practical test is whether someone could understand your page outline from the tag names alone, which is roughly what an assistive technology has to do.

Privacy & Security

All processing happens locally in your browser. Your data never leaves your computer, ensuring complete privacy and security.

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Frequently asked questions

What is Semantic HTML Checker used for?

Check semantic HTML structure for missing landmarks, skipped heading levels and div soup. Paste markup and get a scored, line-referenced report. Free.

Is Semantic HTML Checker free to use?

Yes. Semantic HTML Checker is completely free with no usage limits, and there is no paid tier required to use it.

Do I need an account to use Semantic HTML Checker?

No. Semantic HTML Checker works immediately in your browser with no signup, login, or email address required.

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