MDX 4.0 and the Future of Documentation: What Changed in 2026

The MDX ecosystem has matured significantly since its early days. With MDX 4.0 landing in early 2026, the gap between writing documentation and shipping polished, interactive content has never been smaller.

Here's what's new, what matters, and how it affects your documentation workflow.

The Big Changes in MDX 4.0

Async Components

The most requested feature for years is finally here. MDX 4.0 supports async components natively, meaning you can fetch data during render:

export async function ApiStatus({ endpoint }) {
  const res = await fetch(endpoint);
  const data = await res.json();
  return <span>{data.status}</span>;
}

Check the API: <ApiStatus endpoint="/api/health" />

For static documentation and PDF export, async components resolve at build time. This means your generated PDFs can include live data snapshots without any client-side JavaScript.

Built-in Syntax Highlighting

No more configuring Prism or Shiki separately. MDX 4.0 ships with a lightweight syntax highlighter that covers the most common languages:

def convert_to_pdf(markdown_content: str) -> bytes:
    """Convert markdown to PDF using the mdxtopdf API."""
    response = requests.post(
        "https://mdxtopdf.com/api/generate-pdf",
        json={"mdxText": markdown_content}
    )
    return response.content

The built-in highlighter adds zero client-side JavaScript and works perfectly in PDF output since it generates inline styles rather than relying on CSS classes.

First-Class TypeScript Support

MDX files now support TypeScript annotations out of the box:

interface CardProps {
  title: string;
  description: string;
  href?: string;
}

export function Card({ title, description, href }: CardProps) {
  return (
    <div className="card">
      <h3>{title}</h3>
      <p>{description}</p>
      {href && <a href={href}>Learn more</a>}
    </div>
  );
}

Your editor gets full autocomplete and type checking inside .mdx files. This alone makes MDX viable for large documentation projects where type safety prevents broken component usage.

What This Means for PDF Generation

PDF generation from MDX has always been a two-step process: compile MDX to React components, then render to HTML for the PDF engine. MDX 4.0 simplifies this significantly.

Faster Compilation

The new compiler is 3-4x faster than the v3 compiler. For our MDX to PDF converter, this means:

• Cold start: ~2 seconds faster on serverless (Chromium decompression is still the bottleneck)
• Hot path: Sub-100ms compilation for typical documents
• Large files: Documents over 10,000 words compile in under 500ms

Better Table Rendering

Tables in MDX 3.x had quirks when exported to PDF — column widths sometimes collapsed, and nested content could overflow. The 4.0 renderer produces cleaner HTML table output that PDF engines handle more predictably.

| MDX Version | Table Rendering | PDF Quality | Compilation Speed | |-------------|----------------|-------------|-------------------| | 2.x | Basic | Good | ~800ms | | 3.x | Improved | Good | ~400ms | | 4.0 | Excellent | Excellent | ~100ms |

Print-Optimized Output

MDX 4.0 includes a printOptimized flag that strips interactive elements and adjusts styles for print media:

import { compile } from '@mdx-js/mdx';

const result = await compile(content, {
  printOptimized: true,
  remarkPlugins: [remarkGfm],
});

When enabled, components that rely on browser APIs (event handlers, useState, etc.) are replaced with their static fallbacks automatically.

Migrating from MDX 3.x

If you're running MDX 3.x, the migration is straightforward:

1. Update packages: npm install @mdx-js/mdx@4 @mdx-js/react@4
2. Check custom plugins: Most remark/rehype plugins work unchanged
3. Test component imports: The import resolution algorithm changed slightly — relative imports now resolve from the MDX file location, not the project root

Breaking Changes to Watch

• evaluate() now returns a Promise that includes metadata (word count, headings, reading time)
• The baseUrl option was removed in favor of automatic resolution
• Custom jsx/jsxs factories must now include a Fragment export

The Documentation Toolchain in 2026

The best documentation setup in 2026 looks something like this:

Content (MDX 4.0 files)
    ↓
Build (Next.js / Astro / Vite)
    ↓
Output:
  ├── Web (interactive, searchable)
  ├── PDF (print-ready, shareable)
  └── API (structured data, headless)

Tools like mdxtopdf.com handle the PDF branch of this pipeline. Write once in MDX, publish everywhere — that's the promise, and in 2026, it actually works.

Getting Started

The fastest way to try MDX 4.0 with PDF export:

1. Write your content in MDX (or plain Markdown — it's fully compatible)
2. Paste it into mdxtopdf.com to preview and download as PDF
3. For programmatic use, integrate the compilation pipeline into your CI/CD

The ecosystem is mature, the tooling is fast, and the output quality is finally where it should be. If you've been holding off on MDX for documentation, 2026 is the year to commit.