Developer Tools

Heading Hierarchy Validator — Free, No Upload, Browser-Based

🔒 Runs in your browser

Paste HTML or Markdown and instantly see a visual outline of your h1–h6 heading hierarchy, with plain-English issue reports for skipped levels and multiple h1 tags. Good heading structure matters for both screen-reader accessibility and SEO — this tool catches the most common mistakes before they ship. Everything runs in your browser: no upload, no account, and your markup is never sent anywhere.

How to use this tool

  1. Select HTML or Markdown as the input format, then paste your content into the text area.
  2. The tool parses every h1–h6 heading and checks for skipped levels or multiple h1 tags.
  3. Review the visual outline and fix any flagged issues in your source before publishing.
Input format

1 issue found

  • line 6h4 follows h2 — skips level h3.

Outline (6 headings)

  • h1Page Title:1
  • h2Section A:2
  • h3Subsection A1:3
  • h4Detail:4
  • h2Section B:5
  • h4Skipped h3!:6
h1×1h2×2h3×1h4×2
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Heading Hierarchy Validator — Free, No Upload, Browser-Based | brevio