What is MDX?

MDX is a format that lets you write JSX directly inside Markdown documents. It combines the simplicity of Markdown for content authoring with the power of React components, making it popular for documentation sites, blogs, and content-heavy applications built with frameworks like Next.js, Gatsby, and Docusaurus. An MDX file can contain standard Markdown syntax alongside import statements, exported variables, and inline JSX components — all in a single file.

Unlike plain Markdown, MDX is compiled into JavaScript, which means syntax errors in your JSX or import statements can break the entire document. This makes validation and proper formatting especially important when working with MDX content.

Tool description

The MDX Editor provides a browser-based environment for writing, validating, and formatting MDX content. It features syntax highlighting for both Markdown and JSX, a built-in validator that checks your MDX for compilation errors, and a formatter that cleans up spacing and structure for consistent, readable documents.

Examples

Before formatting:

import {Chart} from './components'
# Dashboard
Some intro text.


Extra blank lines here.
## Section
<Chart data={stats} />

After formatting:

import {Chart} from './components'

# Dashboard

Some intro text.

Extra blank lines here.

## Section

<Chart data={stats} />

Features

  • Syntax highlighting for Markdown and JSX in a single editor
  • MDX validation that checks for compilation errors in real time
  • Automatic formatting that normalizes blank lines and spacing
  • Clear button to quickly reset the editor
  • Copy support for easy export of your formatted content

How it works

  • Validate: Compiles your MDX content using the @mdx-js/mdx compiler. If the document contains syntax errors — such as malformed JSX, unclosed tags, or invalid imports — the validator surfaces the error message so you can fix it.
  • Format: Normalizes whitespace by collapsing multiple consecutive blank lines into one, ensuring blank lines before headings and around import/export blocks, and trimming trailing whitespace. The result is a clean, consistently structured document.

Use cases

  • Writing documentation for React-based projects that use MDX for content pages
  • Debugging MDX compilation errors before deploying a static site
  • Cleaning up MDX files with inconsistent spacing contributed by multiple authors