Paste an HTML document or a fragment to see its heading tree (<h1>–<h6>). The tool flags accessibility and SEO issues — multiple top-level headings, skipped levels (an h2 followed by an h4), empty heading text, headings inside aria-hidden regions, and headings nested in HTML5 sectioning elements that may produce unexpected outlines. Everything runs in your browser; the HTML is parsed in a sandboxed DOMParser — no scripts execute.
Headings inside <template>, <script>, and HTML comments are skipped. Hidden headings (hidden, display:none inline, aria-hidden="true") are reported.
h1 — historically the page title. Most screen-reader navigation patterns and SEO crawlers assume a single, top-level heading per page or article. (Modern HTML5 sectioning allows multiple h1s inside <section>/<article>, but no browser implements the algorithm; treat it as best practice.)h2 straight to h4 breaks screen-reader outline navigation. Use h3 in between, or restructure.alt, only whitespace, or hidden) is announced as an empty stop.h1 is orphaned from the outline.hidden, aria-hidden="true", or inline display:none aren't read by assistive tech, even though they appear in the source outline.