# Analyze an HTML Heading Outline
Paste HTML to extract the H1-H6 heading outline, flag outline issues, and count the element tags written in the source.
## Run it
- **CLI:** `gizza tool html-outline-analyzer '
Guide
Install
Steps...
macOS
Configure
'`
- **Web:** https://gizza.ai/tools/html-outline-analyzer/
- **Agents:** machine-readable descriptor (parameters JSON Schema) at https://gizza.ai/tools/html-outline-analyzer/tool.json
## Inputs
- `html` — HTML _(field)_
- `format` — Output _(field)_
- `min_level` — Minimum heading level _(field)_
- `max_level` — Maximum heading level _(field)_
- `include_issues` — Include outline issues _(field)_
- `include_counts` — Include tag counts _(field)_
- `top_tags` — Tag count rows _(field)_
## Output
- Outline report (text)
## Query parameters
Open the tool pre-filled and auto-run via URL:
- `html` — HTML
- `format` — Output
- `min_level` — Minimum heading level
- `max_level` — Maximum heading level
- `include_issues` — Include outline issues
- `include_counts` — Include tag counts
- `top_tags` — Tag count rows
Example: `https://gizza.ai/tools/html-outline-analyzer/?html=%3C%21doctype%20html%3E%0A%3Chtml%3E%0A%3Cbody%3E%0A%3Ch1%3EGuide%3C%2Fh1%3E%0A%3Ch2%20id%3D%22install%22%3EInstall%3C%2Fh2%3E%0A%3Cp%3ESteps...%3C%2Fp%3E%0A%3Ch3%3EmacOS%3C%2Fh3%3E%0A%3Ch2%3EConfigure%3C%2Fh2%3E%0A%3C%2Fbody%3E%0A%3C%2Fhtml%3E&format=tree&min_level=1&max_level=6&include_issues=true&include_counts=true&top_tags=20`
---
## About this tool
`html-outline-analyzer` reads pasted HTML and reports two things that are useful for SEO, accessibility reviews, documentation cleanups, and migrations: the H1-H6 heading outline, and the element tags used in the source.
The outline keeps document order and records each heading's level, text, `id`, line/column, and hidden state. It also flags common structural problems: missing H1, multiple H1s, skipped heading levels, empty headings, duplicate heading text, and headings hidden with markup such as `hidden`, `aria-hidden="true"`, or inline `display:none`.
### Worked example
Input:
```html
Getting started
Install
Text
macOS
Windows
Configure
Advanced flags
```
Default output includes:
```text
HTML OUTLINE — 6 heading(s)
Levels: h1:1 h2:2 h3:2 h4:1
OUTLINE (6 headings)
1 h1 Getting started
2 h2 Install #install
4 h3 macOS
5 h3 Windows
6 h2 Configure
7 h4 Advanced flags
```
The skipped `h2` → `h4` jump is listed in the issues section, and the tag-count section shows how many `h1`, `h2`, `p`, and other element tags were written.
### Options and limits
- **Output** can be `tree`, `markdown`, `json`, or `csv`.
- **Minimum/maximum heading level** filter the rendered outline without changing the total heading counts.
- **Include outline issues** toggles the issue section.
- **Include tag counts** toggles the total/distinct tag count section.
- **Tag count rows** limits the number of distinct tag names listed, from 1 to 500.
- The input limit is 5 MB and the first 5,000 headings are recorded.
- Counts are based on literal opening/self-closing tags in the source. The scanner does not invent implied DOM elements such as browser-added `` or ``.
- It does not execute JavaScript, fetch linked pages, apply CSS, validate full HTML conformance, or compute the browser accessibility tree.
## FAQ
Is this the same as a browser DOM outline?
No. It scans the literal HTML you paste. That means tag counts reflect the source, not the DOM after a browser inserts implied elements or JavaScript mutates the page. This is useful for audits of generated markup and templates.
Does it use the old HTML5 outline algorithm?
No. The old sectioning algorithm is not implemented by browsers or assistive technology in a way authors can rely on. This tool reports the practical H1-H6 heading sequence and flags skipped levels.
Why is a hidden heading reported?
Hidden headings can affect audits and screen-reader behavior depending on how they are hidden. The analyzer marks headings with `hidden`, `aria-hidden="true"`, or inline styles such as `display:none` and `visibility:hidden` so you can review them explicitly.
Can it analyze a live URL?
No. Paste the HTML source. Keeping the tool paste-only avoids network fetching, login/session problems, and server-side rendering differences. Use your browser's “View Source” or a crawler to collect markup first.
Is my HTML uploaded?
No. The Rust scanner runs locally in the WebAssembly page and in the CLI. Your markup is processed in your browser or terminal.
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