Paste HTML, see the H1-H6 outline as a tree, and get WCAG accessibility warnings for skipped levels, missing H1, and empty headings.
Could not parse HTML
No results found
Paste HTML to audit <img>, <svg>, <input type=image> and role=img elements against WCAG 2.1 alt-text rules.
Paste HTML to see the page's landmark tree (banner/main/nav/aside/footer + ARIA roles) and structural a11y issues.
Paste an HTML form to verify every <input>, <select>, <textarea>, and <button> has an accessible name per WCAG 3.3.2.
A page's heading structure is one of the most important accessibility signals. Screen-reader users navigate by heading (jump between sections); search engines use H1-H6 to understand topic hierarchy. If your page skips from H1 to H3, repeats H1 inside a single article, or uses an empty <h2></h2> for visual spacing, both audiences get lost. The Heading Outline Checker parses pasted HTML, builds an indented tree of every H1-H6, counts them, and flags WCAG 1.3.1 / 2.4.6 issues — directly in your browser, with links to the relevant Understanding documents on w3.org. No upload, no fetch — works on private internal HTML, draft posts, or component snippets.
No H1 found error WCAG 2.4.6 Multiple H1 elements warning WCAG 1.3.1 Empty heading error WCAG 2.4.6 Skipped level (H1 → H3 etc.) warning WCAG 1.3.1 First heading after H1 not H2 warning WCAG 1.3.1