README

rehype

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

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.