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HTML semantic outline checker

Paste HTML and get the heading outline, landmark map, and tiered accessibility findings with fixes, from skipped levels and empty headings to missing main or lang.
HTML source

The scanner is a plain tag reader, not a browser. It does not run scripts, load stylesheets, or see shadow DOM, so hidden state is judged only from the hidden attribute, aria-hidden, and inline display or visibility styles, and heading levels are taken at face value exactly as assistive technology reads them. A paste without an html element is treated as a fragment, and the lang check reports that it could not run rather than guessing. This tool does not check alt text, contrast, labels, or color; the accessible name debugger and keyboard navigation auditor cover parts of that.
Options

More web & auth tools

- Accessible name debugger (/dev/accessible-name-debugger)
- Open graph preview (/web/og-preview)
All web & auth tools (/web)

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Canonical HTML: https://nutter.tools/web/html-semantic-outline-checker
Markdown version: https://nutter.tools/web/html-semantic-outline-checker.md
Plain-text version: https://nutter.tools/web/html-semantic-outline-checker.txt
Agent index: https://nutter.tools/llms.txt