leandrocp

MDEx - Fast and Extensible Markdown

MDEx is a fast and extensible Markdown parser and formatter.

Fast

Leverage Rust to parse, manipulate and render documents using:

comrak - a Rust port of the official GitHub markdown library compliant with the CommonMark spec.
ammonia - HTML sanitization.
autumnus - syntax highlighter powered by Tree-sitter and Neovim themes.

Extensible

A Req-like API to manipulate documents in a pipeline with support for plugins, for eg mdex_mermaid

Features

Fast
Compliant with the CommonMark spec
Plugins
Formats:
- Markdown (CommonMark)
- HTML
- JSON
- XML
- Quill Delta
Floki-like Document AST
Req-like Document pipeline API
GitHub Flavored Markdown
Discord and GitLab Flavored-ish Markdown
Wiki-style links
Streaming incomplete fragments
Emoji shortcodes
Built-in Syntax Highlighting for code blocks
Code Block Decorators
HTML sanitization
~MD Sigil for Markdown, HTML, JSON, XML, and Quill Delta

More at GitHub - leandrocp/mdex: Markdown for Elixir. Fast, Extensible, Phoenix-native. AI-ready. Built on top of comrak, ammonia, and lumis. · GitHub

24 comments

#markdown

26 1928 24

2026-01-21 19:58:59 UTC

First Post!

Eiji

Very interesting package with lots of features that took my attention! Here are just a few questions/suggestions:

It would be nice to see a comparison table with existing solutions like Earmark - short summary side-by-side sometimes does more than thousands of words
Would it be hard to add support for a custom markdown rules or even custom sets of rules (other markdown syntax - if any)? For example see how many interesting features adds ex_doc to the markdown. It’s import to answer if using your library developer could do the same thing. Would it be harder or simpler?
Would it be hard to add support for Earmark (and other packages)? Imagine a case where there is a critical bug in the Rust parser - for Elixir app it means stopping entire app.

If people would prefer your solution then sooner or later they may ask such a questions … Maybe this is not the same kind of feedback you are interested, but since writing parser is not trivial and especially because Earmark is in the ecosystem for a many, many years people working in production may ask you such type of questions.

Instead of forcing something new (i.e. something unknown) it’s always better to provide something that can fallback in the worst case. This often helps in migrating a big part of a project.

Post #1

Most Liked

leandrocp

MDEx v0.9 is now available with some new cool features!

Delta format

Thanks to @Jskalc we can now convert Markdown to Delta:

Streaming

Initial (experimental) support to put incomplete fragments of Markdown into the document. Useful for AI/LLM tools:

You can see a demo (video) at Leandro Pereira on X: "Here's a short demo of Markdown streaming in MDEx 👀 Note it's still experimental and disabled by default. https://t.co/uEdEEalbb8" / X

Inspect Document as a tree

To help visualize the nodes in a document:

It can be disabled if you prefer the regular struct inspect.

Unified Document API

Removed the MDEx.Pipe module in favor of unifying all operations in the MDEx.Document. Note this is a breaking change:

I’ll be working on Support Phoenix tags? · Issue #571 · kivikakk/comrak · GitHub so we can (hopefully) get Elixir and Phoenix components rendering inside Markdown. Enjoy!

Post #15

leandrocp

MDEx v0.7.0 is out with a new ~MD sigils supporting assigns and Elixir expressions:

import MDEx.Sigil

assigns = %{lang: "elixir", sample: "spawn(fn -> send(current, {self(), 1 + 2}) end)"}

~MD"""
## Lang: <%= String.capitalize(@lang) %>

```elixir
<%= @sample %>
```
"""

Outputs:

%MDEx.Document{
  nodes: [
    %MDEx.Heading{nodes: [%MDEx.Text{literal: "Lang: Elixir"}], level: 2, setext: false},
    %MDEx.CodeBlock{
      nodes: [],
      fenced: true,
      fence_char: "`",
      fence_length: 3,
      fence_offset: 0,
      info: "elixir",
      literal: "spawn(fn -> send(current, {self(), 1 + 2}) end)\n"
    }
  ]
}

Or using the HTML modifier:

"<h2>Lang: Elixir</h2>\n<pre class=\"athl\" style=\"color: #abb2bf; background-color: #282c34;\"><code class=\"language-elixir\" translate=\"no\" tabindex=\"0\"><span class=\"line\" data-line=\"1\"><span style=\"color: #61afef;\">spawn</span><span style=\"color: #848b98;\">(</span><span style=\"color: #c678dd;\">fn</span> <span style=\"color: #abb2bf;\">-&gt;</span> <span style=\"color: #61afef;\">send</span><span style=\"color: #848b98;\">(</span><span style=\"color: #abb2bf;\">current</span><span style=\"color: #848b98;\">,</span> <span style=\"color: #848b98;\">&lbrace;</span><span style=\"color: #61afef;\">self</span><span style=\"color: #848b98;\">(</span><span style=\"color: #848b98;\">)</span><span style=\"color: #848b98;\">,</span> <span style=\"color: #d19a66;\">1</span> <span style=\"color: #abb2bf;\">+</span> <span style=\"color: #d19a66;\">2</span><span style=\"color: #848b98;\">&rbrace;</span><span style=\"color: #848b98;\">)</span> <span style=\"color: #c678dd;\">end</span><span style=\"color: #848b98;\">)</span>\n</span></code></pre>"

That’s one step into the direction of supporting Markdown in LiveViews with components.

Post #9

leandrocp

MDEx v0.11 is out with 2 new cool features:

Initial support for Phoenix Components

Now you can render Phoenix Components inside Markdow, either inside a LiveView or just use the ~MD[...]HEEX sigil. Example:

def render(assigns) do
  ~MD"""
  Hello from MDEx :wave:

  Today is _{Calendar.strftime(DateTime.utc_now(), "%B %d, %Y")}_

  <ReqEmbed.embed url={@video_url} class="aspect-video rounded-xl my-6" />

  Built with:
  - <.link href="https://crates.io/crates/comrak">comrak</.link>
  - <.link href="https://hex.pm/packages/mdex">MDEx</.link>
  """HEEX
end

More info at Phoenix LiveView HEEx — MDEx v0.13.2

Syntax Highlighter with Light/Dark themes

The syntax highlighting engine now supports dual/multi themes so you can have automatic light/dark themes:

options = [
  syntax_highlight: [
    formatter: {
      :html_multi_themes,
      themes: [light: "github_light", dark: "github_dark"],
      default_theme: "light-dark()"
    }
  ]
]

Full example at Lumis light/dark theme — MDEx v0.13.2

I’m also opening a sponsorship program if you want to support MDEx in that way please see GitHub - leandrocp/mdex: Markdown for Elixir. Fast, Extensible, Phoenix-native. AI-ready. Built on top of comrak, ammonia, and lumis. · GitHub

Post #18