Implementing Custom MDX Plugins

Demonstrate the implementation of custom MDX plugins in a Next.js project to extend the functionality of MDX.
import remarkHighlight from 'remark-highlight.js';

// next.config.js
module.exports = {
  webpack: (config, { isServer }) => {
    // Fixes npm packages that depend on `fs` module
    if (!isServer) {
      config.node = {
        fs: 'empty'

    return config;
This configuration in next.config.js helps fix the issue regarding the use of 'fs' module in the browser. This is necessary because some plugins might have server-side dependencies which are not available in the client-side bundle.
import remarkMath from 'remark-math';
import rehypeKatex from 'rehype-katex';
import { serialize } from 'next-mdx-remote/serialize';

export async function mdxToHtml(content) {
  return await serialize(content, {
    mdxOptions: {
      remarkPlugins: [remarkMath],
      rehypePlugins: [rehypeKatex],
This code demonstrates how to convert MDX content to HTML using the 'next-mdx-remote' package. It includes the 'remark-math' and 'rehype-katex' plugins to handle mathematical notation in MDX files.
import { MDXProvider } from '@mdx-js/react';
import { mdxToHtml } from './mdxToHtml';

const components = {
  h1: (props) => <h1 style={{ color: 'blue' }} {...props} />, // Custom H1 tag style
  // Other custom components go here

export default function MDXPage({ source }) {
  const content = mdxToHtml(source);
  return (
    <MDXProvider components={components}>
      <div dangerouslySetInnerHTML={{ __html: content }} />
Here we use the 'MDXProvider' from '@mdx-js/react' to pass custom components for the MDX content. The 'mdxToHtml' function is called to convert the MDX source to HTML which is then rendered using 'dangerouslySetInnerHTML' in a React component.
  /* Custom CSS for MDX elements can be placed here */
  h1 {
    color: blue; /* This should match the inline style defined for h1 in MDXProvider */
This is a CSS block defining custom styles for MDX elements. It should ideally be in a CSS file imported in your application, either styled-jsx (which comes with Next.js) or an external CSS.