md4x

# 📄 MD4X

[![npm version][npm version]][npm link]
![][wasm size]

Fast and Small markdown parser and renderer based on [mity/md4c](https://github.com/mity/md4c/).

**[Online Playground](https://md4x.unjs.io/#/playground)**

## Features

- **Fast** — **~8x** faster than markdown-it
- **CLI** — Render local files, remote URLs, GitHub repos, npm packages
- **Small** — **~135KB** gzip WASM binary works in Node.js and Browser
- **Multi-format output** — HTML, JSON AST, ANSI terminal, plain text, markdown, metadata
- **Streaming heal** — Fix incomplete markdown from LLM output in real-time
- **Full CommonMark** — Passes the CommonMark spec
- **GitHub Flavored Markdown** — Tables, task lists, strikethrough, autolinks, alerts
- **Built-in YAML parser** — Frontmatter and standalone YAML, no external dependency
- **Extra extensions** — LaTeX math, highlight (`==mark==`), footnotes, inline attributes
- **Comark (MDC) support** — Block and inline components with props, slots
- **Universal JS** — Native Node.js addon (NAPI) + portable WASM for browsers, Deno, Bun, edge workers
- **Zig library** — SAX-like streaming parser, zero-copy, no AST allocation overhead

## Showcase

- [pi0/mdshot](https://github.com/pi0/mdshot) — Render beautiful screenshots from Markdown.
- [pi0/mdzilla](https://github.com/pi0/mdzilla) — Markdown browser for humans and agents.

## CLI

```sh
# Local files
npx md4x README.md                          # ANSI output
npx md4x README.md -t html                  # HTML output
npx md4x README.md -t text                  # Plain text output (strip markdown)
npx md4x README.md -t ast                   # JSON AST output (comark)
npx md4x README.md -t meta                  # Metadata JSON output
npx md4x README.md -t markdown              # Clean markdown (strip MDC/frontmatter/HTML)
npx md4x README.md -t heal                  # Heal incomplete markdown
npx md4x README.md --heal                   # Heal before rendering (any format)
npx md4x README.md --heal -t ast            # Heal + JSON AST output

# Remote sources
npx md4x https://nitro.build/guide          # Fetch and render any URL
npx md4x gh:nitrojs/nitro                   # GitHub repo → README.md
npx md4x npm:vue@3                          # npm package at specific version

# Stdin
echo "# Hello" | npx md4x -t text
cat README.md | npx md4x  -t html

# Output to file
npx md4x README.md -t meta -o README.json

# Full HTML document
npx md4x README.md -t html -f --html-title="My Docs"  # Wrap in full HTML with <head>
npx md4x README.md -t html -f --html-css=style.css    # Add CSS link
```

### Install from AUR

```sh
yay -S md4x # md4x-git
```

The examples above are the npm CLI (`npx md4x`). The native binary — the one `zig build`
produces and `md4x(1)` documents — is a smaller tool: it reads a local file or stdin, with
no URL, `gh:` or `npm:` shorthands, and its formats are `html` (the default), `text`,
`json`, `ansi`, `markdown` and `heal`, where the npm CLI spells the AST format `ast`