Paste HTML and validate heading tag hierarchy (H1-H6). Detect missing levels, multiple H1s, and incorrect nesting with a visual tree view.
An h1 followed directly by an h3 is easy to miss while reading source. H1-H6 Heading Validator isolates the heading elements in pasted HTML, presents their rank relationships as a visual tree, and reports missing levels, multiple h1 elements, and hierarchy problems. The frequent misunderstanding is that it evaluates markup, not visual size. Text enlarged with CSS is not automatically a heading, while an h2 styled as small text remains an h2. The result helps you review the outline expressed by the HTML.
The validator examines h1 through h6 elements in document order and displays their level relationships. Lower numbers represent higher-level headings, while higher numbers represent increasingly specific subsections. Presenting those transitions as a tree makes an unexpected jump or misplaced subsection easier to see than it would be among paragraphs, links, images, and other markup.
The report calls attention to the specific structural conditions this tool audits. For example, an h2 followed by an h4 leaves h3 absent from that branch, while two h1 elements activate the multiple-h1 finding. These findings identify places for review. They do not rewrite the HTML, evaluate heading wording, or establish what the author intended the sections to mean.
No. A second h1 is not automatically invalid HTML, although one clear page-level h1 is a common authoring convention. This validator reports multiple h1 elements so you can identify accidental competing page titles or unexpectedly combined components. Review the complete page and its intended section structure before treating the finding as something that must be changed.
No. Paragraphs, images, lists, and other content may occur between headings. What matters to this audit is the rank relationship: the h2 should represent a section at the appropriate level beneath the broader structure. The visual tree exposes that relationship, but it cannot determine the intended topic hierarchy, so the final decision requires human review.
The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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