rehype

What is rehype?

Rehype is a powerful HTML processor built on the unified framework. It allows you to parse, transform, and stringify HTML content. It is highly extensible and can be used for a variety of tasks such as sanitizing HTML, extracting content, and transforming HTML structures.

What are rehype's main functionalities?

Parsing HTML

Rehype can parse HTML strings into a syntax tree, which can then be manipulated or analyzed.

const rehype = require('rehype');
const html = '<h1>Hello, world!</h1>';
rehype().parse(html);

Transforming HTML

Rehype allows you to transform HTML content by manipulating the syntax tree. You can use plugins or custom functions to modify the tree.

const rehype = require('rehype');
const html = '<h1>Hello, world!</h1>';
rehype()
  .use(() => (tree) => {
    // Transform the tree
  })
  .process(html)
  .then((file) => {
    console.log(String(file));
  });

Stringifying HTML

Rehype can convert a syntax tree back into an HTML string, allowing you to output the transformed content.

const rehype = require('rehype');
const tree = { type: 'root', children: [{ type: 'element', tagName: 'h1', properties: {}, children: [{ type: 'text', value: 'Hello, world!' }] }] };
rehype().stringify(tree);

Sanitizing HTML

Rehype can be used to sanitize HTML content, removing potentially dangerous elements and attributes.

const rehype = require('rehype');
const rehypeSanitize = require('rehype-sanitize');
const html = '<script>alert("Hello, world!")</script><p>Safe content</p>';
rehype()
  .use(rehypeSanitize)
  .process(html)
  .then((file) => {
    console.log(String(file));
  });

Other packages similar to rehype

htmlparser2

Htmlparser2 is a fast and forgiving HTML/XML parser. It is similar to rehype in that it can parse HTML into a tree structure, but it is more focused on speed and less on extensibility and transformations.

jsdom

Jsdom is a JavaScript implementation of the DOM and HTML standards. It allows you to manipulate HTML content in a way similar to how you would in a browser. Unlike rehype, jsdom provides a full DOM API, making it more suitable for complex manipulations and simulations of browser environments.

cheerio

Cheerio is a fast, flexible, and lean implementation of core jQuery designed specifically for the server. It allows you to parse and manipulate HTML using a jQuery-like syntax. While rehype focuses on transformations and extensibility, cheerio is more about providing a familiar API for DOM manipulation.

README

rehype

unified processor with support for parsing HTML input and serializing HTML as output.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • rehype()
• Examples
  • Example: passing options to rehype-parse, rehype-stringify
• Syntax
• Syntax tree
• Types
• Compatibility
• Security
• Contribute
• Sponsor
• License

What is this?

This package is a unified processor with support for parsing HTML input and serializing HTML as output by using unified with rehype-parse and rehype-stringify.

See the monorepo readme for info on what the rehype ecosystem is.

When should I use this?

You can use this package when you want to use unified, have HTML as input, and want HTML as output. This package is a shortcut for unified().use(rehypeParse).use(rehypeStringify). When the input isn’t HTML (meaning you don’t need rehype-parse) or the output is not HTML (you don’t need rehype-stringify), it’s recommended to use unified directly.

When you’re in a browser, trust your content, don’t need positional info on nodes or formatting options, and value a smaller bundle size, you can use rehype-dom instead.

When you want to inspect and format HTML files in a project on the command line, you can use rehype-cli.

Install

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

npm install rehype

In Deno with Skypack:

import {rehype} from 'https://cdn.skypack.dev/rehype@12?dts'

In browsers with Skypack:

<script type="module">
  import {rehype} from 'https://cdn.skypack.dev/rehype@12?min'
</script>

Use

Say we have the following module example.js:

import {rehype} from 'rehype'
import rehypeFormat from 'rehype-format'

main()

async function main() {
  const file = await rehype()
    .use(rehypeFormat)
    .process(`<!doctype html>
        <html lang=en>
<head>
    <title>Hi!</title>
  </head>
  <body>
    <h1>Hello!</h1>

</body></html>`)

  console.error(String(file))
}

…running that with node example.js yields:

<!doctype html>
<html lang="en">
  <head>
    <title>Hi!</title>
  </head>
  <body>
    <h1>Hello!</h1>
  </body>
</html>

API

This package exports the following identifier: rehype. There is no default export.

rehype()

Create a new (unfrozen) unified processor that already uses rehype-parse and rehype-stringify and you can add more plugins to. See unified for more information.

Examples

Example: passing options to rehype-parse, rehype-stringify

When you use rehype-parse or rehype-stringify manually you can pass options to use. Because both plugins are already used in rehype, that’s not possible. To define options for them, you can instead pass options to data:

import {reporter} from 'vfile-reporter'
import {rehype} from 'rehype'

main()

async function main() {
  const file = await rehype()
    .data('settings', {fragment: true, emitParseErrors: true, preferUnquoted: true})
    .process('<div title="a" title="b"></div>')

  console.error(reporter(file))
  console.log(String(file))
}

…yields:

  1:21-1:21  warning  Unexpected duplicate attribute  duplicate-attribute  parse-error

⚠ 1 warning

<div title=a></div>

Syntax

HTML is parsed according to WHATWG HTML (the living standard), which is also followed by browsers such as Chrome and Firefox.

Syntax tree

The syntax tree format used in rehype is hast.

Types

This package is fully typed with TypeScript. There are no extra types exported.

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.

Security

As rehype works on HTML, and improper use of HTML can open you up to a cross-site scripting (XSS) attack, use of rehype can also be unsafe. Use rehype-sanitize to make the tree safe.

Use of rehype plugins could also open you up to other attacks. Carefully assess each plugin and the risks involved in using them.

For info on how to submit a report, see our security policy.

Contribute

See contributing.md in rehypejs/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

Sponsor

Support this effort and give back by sponsoring on OpenCollective!

Vercel	Motif	HashiCorp	GitBook	Gatsby
Netlify	Coinbase	ThemeIsle	Expo	Boost Note	Holloway
You?

License

MIT © Titus Wormer