react-markdown

remarkjs/react-markdown

README

react-markdown


Build

React component to render markdown.

Feature highlights


safe by default(no dangerouslySetInnerHTML or XSS attacks)
components (pass your own component to use instead of <h2> for ## hi )
plugins (many plugins you can pick and choose from)
compliant (100% to CommonMark, 100% to GFM with a plugin)

Contents


What is this?
When should I use this?
Install
Use
API
props
uriTransformer

Examples
Use a plugin
Use a plugin with options
Use custom components (syntax highlight)
Use remark and rehype plugins (math)

Plugins
Syntax
Types
Compatibility
Architecture
Appendix A: HTML in markdown
Appendix B: Components
Security
Related
Contribute
License

What is this?


This package is a React component that can be given a string of markdown that it’ll safely render to React elements. You can pass plugins to change how markdown is transformed to React elements and pass components that will be used instead of normal HTML elements.

to learn markdown, see this cheatsheet and tutorial
to try out react-markdown, see our demo

When should I use this?


There are other ways to use markdown in React out there so why use this one? The two main reasons are that they often rely on dangerouslySetInnerHTML or have bugs with how they handle markdown. react-markdown uses a syntax tree to build the virtual dom which allows for updating only the changing DOM instead of completely overwriting. react-markdown is 100% CommonMark compliant and has plugins to support other syntax extensions (such as GFM).

These features are supported because we use unified, specifically remark for markdown and rehype for HTML, which are popular tools to transform content with plugins.

This package focusses on making it easy for beginners to safely use markdown in React. When you’re familiar with unified, you can use a modern hooks based alternative react-remark or rehype-react manually. If you instead want to use JavaScript and JSX insidemarkdown files, use MDX.

Install


This package is ESM only. In Node.js (version 12.20+, 14.14+, or 16.0+), install with npm :

  1. ``` shell
  2. npm install react-markdown
  3. ```

In Deno with esm.sh :

  1. ``` js
  2. import ReactMarkdown from 'https://esm.sh/react-markdown@7'
  3. ```

In browsers with esm.sh :

  1. ``` html
  2. <script type="module">
  3.   import ReactMarkdown from 'https://esm.sh/react-markdown@7?bundle'
  4. </script>
  5. ```

Use


A basic hello world:

  1. ``` js
  2. import React from 'react'
  3. import ReactMarkdown from 'react-markdown'
  4. import ReactDom from 'react-dom'

  6. ReactDom.render(<ReactMarkdown># Hello, *world*!, document.body)
  7. ```

Show equivalent JSX
  1. ``` js
  2. <h1>
  3.   Hello, <em>world</em>!
  4. </h1>
  5. ```

Here is an example that shows passing the markdown as a string and how to use a plugin (remark-gfm, which adds support for strikethrough, tables, tasklists and URLs directly):

  1. ``` js
  2. import React from 'react'
  3. import ReactDom from 'react-dom'
  4. import ReactMarkdown from 'react-markdown'
  5. import remarkGfm from 'remark-gfm'

  7. const markdown = `Just a link: https://reactjs.com.`

  9. ReactDom.render(
  10.   <ReactMarkdown children={markdown} remarkPlugins={[remarkGfm]} />,
  11.   document.body
  12. )
  13. ```

Show equivalent JSX
  1. ``` js
  2. <p>
  3.   Just a link: <a href="https://reactjs.com">https://reactjs.com.
  4. </p>
  5. ```

API


This package exports the following identifier: uriTransformer. The default export is ReactMarkdown.

props


children (string, default: '' )markdown to parse
components (Record<string, Component>, default: {} )object mapping tag names to React components
remarkPlugins (Array<Plugin>, default: [] )list of remark plugins to use
rehypePlugins (Array<Plugin>, default: [] )list of rehype plugins to use
remarkRehypeOptions (Object?, default: undefined )options to pass through to remark-rehype
className (string? )wrap the markdown in a div with this class name
skipHtml (boolean, default: false )ignore HTML in markdown completely
sourcePos (boolean, default: false )pass a prop to all components with a serialized position (data-sourcepos="3:1-3:13" )
rawSourcePos (boolean, default: false )pass a prop to all components with their position (sourcePosition: {start: {line: 3, column: 1}, end:…} )
includeElementIndex (boolean, default: false )pass the index (number of elements before it) and siblingCount (number of elements in parent) as props to all components
allowedElements (Array<string>, default: undefined )tag names to allow (can’t combine w/ disallowedElements ), all tag names are allowed by default
disallowedElements (Array<string>, default: undefined )tag names to disallow (can’t combine w/ allowedElements ), all tag names are allowed by default
allowElement ((element, index, parent) => boolean?, optional)function called to check if an element is allowed (when truthy) or not, allowedElements or disallowedElements is used first!
unwrapDisallowed (boolean, default: false )extract (unwrap) the children of not allowed elements, by default, when strong is disallowed, it and it’s children are dropped, but with unwrapDisallowed the element itself is replaced by its children
linkTarget (string or (href, children, title) => string, optional)target to use on links (such as _blank for <a target="_blank"… )
transformLinkUri ((href, children, title) => string, default: uriTransformer, optional)change URLs on links, pass null to allow all URLs, see security
transformImageUri ((src, alt, title) => string, default: uriTransformer, optional)change URLs on images, pass null to allow all URLs, see security

uriTransformer


Our default URL transform, which you can overwrite (see props above). It’s given a URL and cleans it, by allowing only http:, https:, mailto:, and tel: URLs, absolute paths (/example.png ), and hashes (#some-place ).

See the source code here.

Examples


Use a plugin


This example shows how to use a remark plugin. In this case, remark-gfm, which adds support for strikethrough, tables, tasklists and URLs directly:

  1. ``` js
  2. import React from 'react'
  3. import ReactMarkdown from 'react-markdown'
  4. import ReactDom from 'react-dom'
  5. import remarkGfm from 'remark-gfm'

  7. const markdown = `A paragraph with *emphasis* and **strong importance**.

  9. > A block quote with ~strikethrough~ and a URL: https://reactjs.org.

  11. * Lists
  12. * [ ] todo
  13. * [x] done

  15. A table:

  17. | a | b |
  18. | - | - |
  19. `

  21. ReactDom.render(
  22.   <ReactMarkdown children={markdown} remarkPlugins={[remarkGfm]} />,
  23.   document.body
  24. )
  25. ```

Show equivalent JSX
  1. ``` js
  2. <>
  3.   <p>
  4.     A paragraph with <em>emphasis</em> and strong importancestrong>.
  5.   </p>
  6.   <blockquote>
  7.     <p>
  8.       A block quote with <del>strikethrough</del> and a URL:{' '}
  9.       <a href="https://reactjs.org">https://reactjs.org.
  10.     </p>
  11.   </blockquote>
  12.   <ul>
  13.     <li>Lists</li>
  14.     <li>
  15.       <input checked={false} readOnly={true} type="checkbox" /> todo
  16.     </li>
  17.     <li>
  18.       <input checked={true} readOnly={true} type="checkbox" /> done
  19.     </li>
  20.   </ul>
  21.   <p>A table:</p>
  22.   <table>
  23.     <thead>
  24.       <tr>
  25.         <td>a</td>
  26.         <td>b</td>
  27.       </tr>
  28.     </thead>
  29.   </table>
  30. </>
  31. ```

Use a plugin with options


This example shows how to use a plugin and give it options. To do that, use an array with the plugin at the first place, and the options second. remark-gfm has an option to allow only double tildes for strikethrough:

  1. ``` js
  2. import React from 'react'
  3. import ReactMarkdown from 'react-markdown'
  4. import ReactDom from 'react-dom'
  5. import remarkGfm from 'remark-gfm'

  7. ReactDom.render(
  8.   <ReactMarkdown remarkPlugins={[[remarkGfm, {singleTilde: false}]]}>
  9.     This ~is not~ strikethrough, but ~~this is~~!
  10.   </ReactMarkdown>,
  11.   document.body
  12. )
  13. ```

Show equivalent JSX
  1. ``` js
  2. <p>
  3.   This ~is not~ strikethrough, but <del>this is</del>!
  4. </p>
  5. ```

Use custom components (syntax highlight)


This example shows how you can overwrite the normal handling of an element by passing a component. In this case, we apply syntax highlighting with the seriously super amazing react-syntax-highlighter by @conorhastings :

  1. ``` js
  2. import React from 'react'
  3. import ReactDom from 'react-dom'
  4. import ReactMarkdown from 'react-markdown'
  5. import {Prism as SyntaxHighlighter} from 'react-syntax-highlighter'
  6. import {dark} from 'react-syntax-highlighter/dist/esm/styles/prism'

  8. // Did you know you can use tildes instead of backticks for code in markdown? ✨
  9. const markdown = `Here is some JavaScript code:

  11. ~~~js
  12. console.log('It works!')
  13. ~~~
  14. `

  16. ReactDom.render(
  17.   <ReactMarkdown
  18.     children={markdown}
  19.     components={{
  20.       code({node, inline, className, children, ...props}) {
  21.         const match = /language-(\w+)/.exec(className || '')
  22.         return !inline && match ? (
  23.           <SyntaxHighlighter
  24.             children={String(children).replace(/\n$/, '')}
  25.             style={dark}
  26.             language={match[1]}
  27.             PreTag="div"
  28.             {...props}
  29.           />
  30.         ) : (
  31.           <code className={className} {...props}>
  32.             {children}
  33.           </code>
  34.         )
  35.       }
  36.     }}
  37.   />,
  38.   document.body
  39. )
  40. ```

Show equivalent JSX
  1. ``` js
  2. <>
  3.   <p>Here is some JavaScript code:</p>
  4.   <pre>
  5.     <SyntaxHighlighter language="js" style={dark} PreTag="div" children="console.log('It works!')" />
  6.   </pre>
  7. </>
  8. ```

Use remark and rehype plugins (math)


This example shows how a syntax extension (through remark-math ) is used to support math in markdown, and a transform plugin (rehype-katex ) to render that math.

  1. ``` js
  2. import React from 'react'
  3. import ReactDom from 'react-dom'
  4. import ReactMarkdown from 'react-markdown'
  5. import remarkMath from 'remark-math'
  6. import rehypeKatex from 'rehype-katex'

  8. import 'katex/dist/katex.min.css' // `rehype-katex` does not import the CSS for you

  10. ReactDom.render(
  11.   <ReactMarkdown
  12.     children={`The lift coefficient ($C_L$) is a dimensionless coefficient.`}
  13.     remarkPlugins={[remarkMath]}
  14.     rehypePlugins={[rehypeKatex]}
  15.   />,
  16.   document.body
  17. )
  18. ```

Show equivalent JSX
  1. ``` js
  2. <p>
  3.   The lift coefficient (
  4.   <span className="math math-inline">
  5.     <span className="katex">
  6.       <span className="katex-mathml">
  7.         <math xmlns="http://www.w3.org/1998/Math/MathML">{/* … */}</math>
  8.       </span>
  9.       <span className="katex-html" aria-hidden="true">
  10.         {/* … */}
  11.       </span>
  12.     </span>
  13.   </span>
  14.   ) is a dimensionless coefficient.
  15. </p>
  16. ```

Plugins


We use unified, specifically remark for markdown and rehype for HTML, which are tools to transform content with plugins. Here are three good ways to find plugins:

awesome-remark and awesome-rehype — selection of the most awesome projects
List of remark plugins and list of rehype plugins — list of all plugins
remark-plugin and rehype-plugin topics — any tagged repo on GitHub

Syntax


react-markdown follows CommonMark, which standardizes the differences between markdown implementations, by default. Some syntax extensions are supported through plugins.

We use micromark under the hood for our parsing. See its documentation for more information on markdown, CommonMark, and extensions.

Types


This package is fully typed with TypeScript. It exports Options and Components types, which specify the interface of the accepted props and components.

Compatibility


Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, and 16.0+. Our projects sometimes work with older versions, but this is not guaranteed. They work in all modern browsers (essentially: everything not IE 11). You can use a bundler (such as esbuild, webpack, or Rollup) to use this package in your project, and use its options (or plugins) to add support for legacy browsers.

Architecture


  1. ``` sh
  2.                                                            react-markdown
  3.          +----------------------------------------------------------------------------------------------------------------+
  4.          |                                                                                                                |
  5.          |  +----------+        +----------------+        +---------------+       +----------------+       +------------+ |
  6.          |  |          |        |                |        |               |       |                |       |            | |
  7. markdown-+->+  remark  +-mdast->+ remark plugins +-mdast->+ remark-rehype +-hast->+ rehype plugins +-hast->+ components +-+->react elements
  8.          |  |          |        |                |        |               |       |                |       |            | |
  9.          |  +----------+        +----------------+        +---------------+       +----------------+       +------------+ |
  10.          |                                                                                                                |
  11.          +----------------------------------------------------------------------------------------------------------------+

  13. ```

To understand what this project does, it’s important to first understand what unified does: please read through the unifiedjs/unified readme (the part until you hit the API section is required reading).

react-markdown is a unified pipeline — wrapped so that most folks don’t need to directly interact with unified. The processor goes through these steps:

parse markdown to mdast (markdown syntax tree)
transform through remark (markdown ecosystem)
transform mdast to hast (HTML syntax tree)
transform through rehype (HTML ecosystem)
render hast to React with components

Appendix A: HTML in markdown


react-markdown typically escapes HTML (or ignores it, with skipHtml ) because it is dangerous and defeats the purpose of this library.

However, if you are in a trusted environment (you trust the markdown), and can spare the bundle size (±60kb minzipped), then you can use rehype-raw :

  1. ``` js
  2. import React from 'react'
  3. import ReactDom from 'react-dom'
  4. import ReactMarkdown from 'react-markdown'
  5. import rehypeRaw from 'rehype-raw'

  7. const input = `<div class="note">

  9. Some *emphasis* and strong!

  11. </div>`

  13. ReactDom.render(
  14.   <ReactMarkdown rehypePlugins={[rehypeRaw]} children={input} />,
  15.   document.body
  16. )
  17. ```

Show equivalent JSX
  1. ``` js
  2. <div class="note">
  3.   <p>Some <em>emphasis</em> and strongstrong>!</p>
  4. </div>
  5. ```

Note: HTML in markdown is still bound by how HTML works inCommonMark. Make sure to use blank lines around block-level HTML that again contains markdown!

Appendix B: Components


You can also change the things