Non-standard fork of rehype plugin to parse HTML

Usage no npm install needed!

<script type="module">
  import rehypeParseNs from '';



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A fork of the original rehype plugin to parse HTML. This one allows uppercase tag names and attributes, useful when parsing non-standard html files. See parse5-ns and hast-util-from-parse5-ns for more information.

Parser for unified. Parses HTML to hast syntax trees. Used in the rehype processor but can be used on its own as well.


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This package is ESM only: Node 12+ is needed to use it and it must be imported instead of required.


npm install rehype-parse-ns


This example shows how we can parse HTML with this module and configure it to emit parse errors except for duplicate attributes. Then we transform HTML to Markdown with rehype-remark and finally serialize that Markdown with remark-stringify.

Say we have the following file, example.html, with a few errors:

<title class="a" class="b">Hello…</title>

…and our script, example.js, looks as follows:

import {readSync} from 'to-vfile'
import {reporter} from 'vfile-reporter'
import {unified} from 'unified'
import rehypeParse from 'rehype-parse-ns'
import rehypeRemark from 'rehype-remark'
import remarkStringify from 'remark-stringify'

const file = readSync('example.html')

  .use(rehypeParse, {emitParseErrors: true, duplicateAttribute: false})
  .then((file) => {

Now, running node example yields:

  1:10-1:10  warning  Missing whitespace before doctype name                      missing-whitespace-before-doctype-name                 parse-error
    3:1-3:6  warning  Unexpected trailing slash on start tag of non-void element  non-void-html-element-start-tag-with-trailing-solidus  parse-error

⚠ 2 warnings
# World!


This package exports no identifiers. The default export is rehypeParse.

unified().use(rehypeParse[, options])

Configure processor to parse HTML and create a hast syntax tree.


Specify whether to parse a fragment (boolean, default: false), instead of a complete document. In document mode, unopened html, head, and body elements are opened in just the right places.

⚠️ rehype is not an XML parser. It support SVG as embedded in HTML, but not the features available in the rest of XML/SVG. Passing SVG files could strip useful information, but fragments of modern SVG should be fine.

Which space the document is in ('svg' or 'html', default: 'html').

If an svg element is found in the HTML space, parse automatically switches to the SVG space when entering the element, and switches back when exiting.

Note: make sure to set fragment: true if space: 'svg'.


⚠️ Parse errors are currently being added to HTML. Not all errors emitted by parse5 (or rehype-parse) are specced yet. Some documentation may still be missing.

Emit parse errors while parsing on the vfile (boolean, default: false).

Setting this to true starts emitting HTML parse errors.

Specific rules can be turned off by setting them to false (or 0). The default, when emitParseErrors: true, is true (or 1), and means that rules emit as warnings. Rules can also be configured with 2, to turn them into fatal errors.

The specific parse errors that are currently supported are detailed below:


Patch extra positional information (boolean, default: false). If specified, the following element:

<img src="#" alt>

…has the following data:

{ position:
   { opening:
      { start: { line: 1, column: 1, offset: 0 },
        end: { line: 1, column: 18, offset: 17 } },
     closing: null,
      { src:
         { start: { line: 1, column: 6, offset: 5 },
           end: { line: 1, column: 13, offset: 12 } },
         { start: { line: 1, column: 14, offset: 13 },
           end: { line: 1, column: 17, offset: 16 } } } } }


Access to the parser, if you need it.


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.


See in rehypejs/.github for ways to get started. See for ways to get help. Ideas for new plugins and tools can be posted in rehypejs/ideas.

A curated list of awesome rehype resources can be found in awesome rehype.

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


MIT Β© Titus Wormer