Heading Structure Analyzer
Paste a full page or a fragment of HTML and get the complete heading outline as a tree, plus an issues panel that flags missing H1s, duplicate H1s, skipped levels, and empty headings.
Parsed locally with DOMParser, no scripts run, nothing is uploaded.
How the analyzer reads your outline
The tool parses your HTML into an inert document with the browser's DOMParser, so no scripts in the pasted code ever run, then walks every h1 through h6 in document order. Each heading is indented by its level to reconstruct the outline a search engine or screen reader would infer. The issues panel then checks that outline against the rules that matter: exactly one H1, no skipped levels, no empty headings, and no headings so long they stop functioning as labels.
What a good heading vector looks like
- One H1 stating the scope. It names the page's central entity and promise, and everything below it elaborates that claim.
- H2s as the macro arc. Read in sequence, the H2s alone should tell the page's whole story, each one a distinct subtopic, none redundant.
- H3s as micro elaboration. Each H3 unpacks its parent H2 and nothing else. If an H3 belongs to a different H2, the structure is wrong, not the heading.
- No decorative headings. If text is styled as a heading purely for size, it should be a styled paragraph instead. Heading tags are structure, not typography.
Frequently asked questions
Does heading order matter for SEO?
Yes, in a practical sense. Headings are one of the clearest signals search engines and AI systems use to understand what a page covers and how its topics relate. A clean hierarchy, one H1 stating the page's scope and H2s breaking it into subtopics, helps crawlers map the content, win passage-level rankings, and get sections cited correctly.
Are multiple H1s an error in 2026?
Not technically. HTML5 allows multiple H1s and Google has said pages with several can still rank. SEO best practice is still a single H1: one heading that states the page's scope makes the topic unambiguous for search engines, screen readers, and AI answer engines, while multiple H1s split that signal.
Do skipped heading levels hurt?
They are not a ranking penalty, but they are an accessibility and clarity problem. Jumping from an H2 straight to an H4 breaks the document outline screen-reader users navigate by, and it muddies the parent-child relationships machines infer from the hierarchy. Fixing skips costs nothing and removes ambiguity.
Is my HTML uploaded anywhere?
No. The HTML is parsed in your browser with the DOMParser API, in an inert document where no scripts execute. Nothing is sent to a server, stored, or logged, so pasting unpublished or client pages is safe.