Markdown header sorter

Sort markdown sections alphabetically by heading text. Use it online or run the script in Node. No build step, no dependencies.

Try it

Open the app →

Paste markdown, choose a header level (# to ######) or “All headers,” and get sections sorted A–Z. Copy the result with one click.

Features

• Recursive sort — Sort all header levels at once; nested structure is preserved and sorted at each level.
• Single-level sort — Sort only #, ##, ###, etc., leaving other levels unchanged.
• Live output — Result updates as you type.
• No backend — Runs entirely in the browser (or in Node for the core logic).
• Free and open source — No account, no install for the web app.

Format requirements

Headers are only detected when they have a blank line above and below:

# Topic

## My topic

## My other topic

Without blank lines around headers, the sorter won’t see them.

Run locally

Web app

From the project root, start the included Node server (no extra packages):

node server.js

Then open http://localhost:3000 in your browser. To use another port, pass it as an argument or set PORT:

node server.js 8080
# or
PORT=8080 node server.js

Core logic (Node)

The sorting logic is in recursiveSort.js and can be used in Node:

const { sortMarkdownHeaders } = require('./js/recursiveSort.js');

const markdown = `
# B
B content

# A
A content
`;

console.log(sortMarkdownHeaders(markdown, { level: 'all' }));
// Output: # A ... # B ...

API: sortMarkdownHeaders(input, options)

• input — Raw markdown string.
• options.level — 'all' (recursive) or 1–6 (sort only that header level).
• Returns the sorted markdown string.

Tests

Run the test suite (Node):

node tests/sortMarkdown.test.js

Project structure

├── index.html
├── server.js              # Local static server (node server.js)
├── css/
│   ├── normalize.css
│   └── style.css
├── js/
│   ├── recursiveSort.js   # Core: parse, sort, serialize (browser + Node)
│   └── app.js             # Page logic: examples, toolbar, persistence
├── tests/
│   └── sortMarkdown.test.js
├── images/                # Favicons, PWA icons, web manifest
├── assets/
│   └── audio/            # Easter egg audio
├── archive/             # Old backup (e.g. index-original.html)
├── sitemap.xml
└── robots.txt

Vanilla JS and CSS; no build step.

Author

Lukas Dzenkauskas
GitHub · Buy me a coffee

License

MIT (see repository for details).