MDX: A Deep Dive into Markdown for the Modern Web

In today's content-driven web, the ability to merge content and interactivity has become essential. Traditional Markdown is great for writing static content, while modern web applications thrive on dynamic components and reusable UI patterns. This is where MDX—Markdown for the component era—steps in.

What is MDX?

MDX is a file format that lets you write JSX (React components) directly inside Markdown. Instead of treating Markdown and React as separate layers, MDX merges them into one cohesive language, allowing content writers and developers to collaborate more effectively.

With MDX, you can write content like this:

# Hello, World!

This is a markdown paragraph.

<CustomComponent prop="value" />

This file is no longer just a content blob; it’s a valid React component that can be rendered directly.

How MDX Works Under the Hood

At its core, MDX is a compiler that transforms .mdx files into standard JavaScript React components. Here’s a more technical breakdown of the compilation process:

1. Markdown Tokenization & Parsing: MDX uses micromark, a fast and spec-compliant Markdown tokenizer. It converts raw Markdown into a sequence of tokens and generates an Abstract Syntax Tree (AST) using mdast(Markdown AST).

2. JSX Parsing: The MDX parser also integrates estree and Babel to parse embedded JSX and JavaScript expressions. JSX is handled as part of the content tree rather than isolated blocks.

3. AST Transformation: The Markdown AST and the JSX syntax tree are combined and transformed into a hast(HTML AST). Then it's converted into estree, which is JavaScript-compatible.

4. Code Generation: The final JavaScript AST is compiled into React component code using Babel. This code can then be bundled by your framework (e.g., Next.js, Vite) and rendered as part of your app.

By precompiling MDX to React components at build time, MDX avoids runtime interpretation and achieves excellent performance.

Why Use MDX?

• Component Interactivity: Embed live charts, input fields, buttons, and other interactive components directly in your Markdown content.

• Single Source of Truth: Keep your content and UI logic in the same file for cohesive design and easier maintenance.

• Typed & Reusable: Since MDX compiles to React, you can type-check, reuse, and compose your content just like any component.

• Extensible Rendering: Customize how headings, paragraphs, code blocks, etc., are rendered using MDXProvider.

• Static Site Optimization: With build-time compilation, content becomes part of the static bundle, improving performance.

Using MDX with Next.js

Next.js offers first-class support for MDX through official and community packages like @next/mdx and next-mdx-remote. Here’s how to set it up using @next/mdx:

1. Install the necessary packages

npm install @next/mdx @mdx-js/loader @mdx-js/react

2. Update your next.config.js

const withMDX = require('@next/mdx')({ extension: /\.mdx?$/ });

module.exports = withMDX({
  pageExtensions: ['js', 'jsx', 'ts', 'tsx', 'md', 'mdx'],
});

3. Create a component

// components/Counter.js
import { useState } from 'react';

export default function Counter() {
  const [count, setCount] = useState(0);
  return <button onClick={() => setCount(count + 1)}>Count: {count}</button>;
}

4. Use the component inside an MDX file

// pages/example.mdx
import Counter from '../components/Counter';

# My Interactive Post

This is a counter embedded directly in markdown:

<Counter />

You can navigate to /example in your browser to view your dynamic MDX page.

Customizing MDX Output with MDXProvider

The @mdx-js/react package allows customization of rendered markdown elements using MDXProvider.

// pages/_app.js
import { MDXProvider } from '@mdx-js/react';

const components = {
  h1: (props) => <h1 style={{ color: 'tomato' }} {...props} />,
  p: (props) => <p style={{ fontSize: '18px' }} {...props} />,
};

export default function App({ Component, pageProps }) {
  return (
    <MDXProvider components={components}>
      <Component {...pageProps} />
    </MDXProvider>
  );
}

This gives you control over how markdown elements are rendered throughout your site.

SEO Benefits of MDX

One of the key concerns with using component-driven content is SEO. MDX addresses this by compiling to semantic HTML and enabling static rendering. Here’s how MDX supports SEO:

• Server-side Rendering (SSR) and Static Generation (SSG): MDX integrates seamlessly with Next.js's SSR/SSG, allowing you to serve fully rendered HTML to crawlers.

• Semantic HTML Output: Headings (<h1> to <h6>), paragraphs (<p>), lists (<ul>, <ol>), and other markdown structures are rendered with proper tags.

• Custom Metadata Support: Use next/head within MDX pages to add meta tags, Open Graph data, and more.

• Improved Page Performance: Precompiled static content loads faster, improving Core Web Vitals, which impacts search rankings.

• Content Discoverability: You can insert JSON-LD structured data components directly in MDX to help search engines understand and categorize your content.

Use Cases for MDX

• Blogs and Personal Sites: Add components like newsletter forms, YouTube embeds, or product cards inline with your content.

• Technical Documentation: Mix prose with live component demos or code playgrounds.

• Course Platforms: Deliver lessons with interactive components, quizzes, and progress trackers.

• Design Systems: Document UI components alongside live previews and usage examples.

• Product Documentation & Changelogs: MDX is especially useful for maintaining and rendering product documentation. You can version your docs, include interactive code examples, and add changelogs in a single source of truth. Since it's treated like code, every update can go through pull requests and version control, making the review process seamless.

  Companies like Vercel, HashiCorp, and Stripe use MDX for parts of their documentation sites. For example, Vercel's documentation integrates React components into Markdown pages to offer interactive examples and dynamic navigation, all managed in .mdx files.

Final thoughts

MDX is more than just a Markdown extension—it’s a powerful way to bring interactivity and reusability to your content. By compiling to React components, MDX allows developers to treat content as part of the application, enabling dynamic and customized experiences while retaining the simplicity of Markdown.

When combined with a powerful framework like Next.js, MDX becomes a production-ready tool for content-driven apps that care about performance, SEO, and maintainability. Whether you’re building blogs, documentation, or interactive tutorials, MDX equips you with the flexibility and power to do it right.

- Jagadhiswaran devaraj

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