astromd4x

Drop-in replacement for @astrojs/markdown-remark powered by md4x.

undefined~50-70x faster markdown rendering with a single native dependency.

Benchmarks

Scenario	astromd4x	@astrojs/markdown-remark	Speedup
createMarkdownProcessor	11.8M ops/s	1.8M ops/s	undefined6.5xundefined
render: simple	443K ops/s	8.2K ops/s	undefined53.7xundefined
render: with frontmatter	155K ops/s	4.5K ops/s	undefined34.5xundefined
render: complex document	49K ops/s	670 ops/s	undefined73xundefined

Usage

Install the package:

npx nypm install astromd4x

Override @astrojs/markdown-remark in your root package.json:

{
  "pnpm": {
    "overrides": {
      "@astrojs/markdown-remark": "npm:astromd4x@latest"
    }
  }
}

Or use directly:

import { createMarkdownProcessor, parseFrontmatter } from "astromd4x";

const processor = await createMarkdownProcessor();
const { code, metadata } = await processor.render("# Hello World");

console.log(code); // <h1 id="hello-world">Hello World</h1>
console.log(metadata.headings); // [{ depth: 1, slug: 'hello-world', text: 'Hello World' }]

API

createMarkdownProcessor(opts?)

Creates a reusable markdown processor. Returns { render(content, opts?) }.

const processor = await createMarkdownProcessor();
const result = await processor.render(markdown);
// result.code - HTML string
// result.metadata.headings - { depth, slug, text }[]
// result.metadata.frontmatter - Record<string, any>

parseFrontmatter(code, options?)

Parses YAML frontmatter from markdown content.

const { frontmatter, rawFrontmatter, content } = parseFrontmatter(markdown);

Options for frontmatter: 'preserve' | 'remove' (default) | 'empty-with-spaces' | 'empty-with-lines'

extractFrontmatter(code)

Returns raw frontmatter string or undefined.

isFrontmatterValid(frontmatter)

Returns true if the frontmatter object is JSON-serializable.

markdownConfigDefaults / syntaxHighlightDefaults

Default configuration objects matching @astrojs/markdown-remark defaults.

Features

• GFM (tables, task lists, strikethrough, autolinks)
• YAML frontmatter parsing
• Heading ID generation (github-slugger compatible)
• Heading metadata extraction
• Full type compatibility with @astrojs/markdown-remark

Current Limitations

This is an early release focused on core rendering performance. Some @astrojs/markdown-remark features are not yet implemented:

• Shiki/Prism syntax highlighting (md4x supports a highlighter callback — wiring planned)
• Remark/Rehype plugin pipeline
• Image path collection (localImagePaths/remoteImagePaths)
• Smartypants typography
• TOML frontmatter

See plan.md for the full roadmap.

Development

local development

• Clone this repository
• Install latest LTS version of Node.js
• Enable Corepack using corepack enable
• Install dependencies using pnpm install
• Run interactive tests using pnpm dev
• Run benchmarks using pnpm vitest bench test/bench.bench.ts

License

Published under the MIT license.