rehype-external-links

What is rehype-external-links?

The rehype-external-links package is a plugin for the rehype ecosystem that allows you to easily add attributes to external links in your HTML. This can be useful for adding security features like `rel='noopener noreferrer'` or styling external links differently.

What are rehype-external-links's main functionalities?

Add target='_blank' to external links

This feature allows you to automatically add `target='_blank'` to all external links, making them open in a new tab.

const rehype = require('rehype');
const rehypeExternalLinks = require('rehype-external-links');

rehype()
  .use(rehypeExternalLinks, { target: '_blank' })
  .process('<a href="https://example.com">Example</a>', function (err, file) {
    if (err) throw err;
    console.log(String(file));
  });

Add rel='noopener noreferrer' to external links

This feature allows you to add `rel='noopener noreferrer'` to all external links, which is a security best practice to prevent the new page from being able to access the window.opener property.

const rehype = require('rehype');
const rehypeExternalLinks = require('rehype-external-links');

rehype()
  .use(rehypeExternalLinks, { rel: ['noopener', 'noreferrer'] })
  .process('<a href="https://example.com">Example</a>', function (err, file) {
    if (err) throw err;
    console.log(String(file));
  });

Customize attributes for external links

This feature allows you to customize multiple attributes for external links, including adding custom content like ' (external)' to the link text.

const rehype = require('rehype');
const rehypeExternalLinks = require('rehype-external-links');

rehype()
  .use(rehypeExternalLinks, { target: '_blank', rel: ['noopener', 'noreferrer'], content: ' (external)' })
  .process('<a href="https://example.com">Example</a>', function (err, file) {
    if (err) throw err;
    console.log(String(file));
  });

Other packages similar to rehype-external-links

rehype-autolink-headings

rehype-autolink-headings is a plugin that automatically adds links to headings in your HTML. Although its primary use case is different, it shares the common goal of enhancing HTML content by adding links.

rehype-rewrite

rehype-rewrite is a plugin that allows you to rewrite HTML nodes. It provides a more flexible and powerful way to manipulate HTML, including adding attributes to external links, but requires more configuration compared to rehype-external-links.

README

rehype-external-links

rehype plugin to add rel (and target) to external links.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • unified().use(rehypeExternalLinks[, options])
• Types
• Compatibility
• Security
• Contribute
• License

What is this?

This package is a unified (rehype) plugin to add rel (and target) attributes to external links. It is particularly useful when displaying user content on your reputable site, because users could link to disreputable sources (spam, scams, etc), as search engines and other bots will discredit your site for linking to them (or legitimize their sites). In short: linking to something signals trust, but you can’t trust users. This plugin adds certain rel attributes to prevent that from happening.

unified is a project that transforms content with abstract syntax trees (ASTs). rehype adds support for HTML to unified. hast is the HTML AST that rehype uses. This is a rehype plugin that adds rel (and target) to <a>s in the AST.

When should I use this?

This project is useful when you want to display user content from authors you don’t trust (such as comments), as they might include links you don’t endorse, on your website.

Install

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

npm install rehype-external-links

In Deno with Skypack:

import rehypeExternalLinks from 'https://cdn.skypack.dev/rehype-external-links@1?dts'

In browsers with Skypack:

<script type="module">
  import rehypeExternalLinks from 'https://cdn.skypack.dev/rehype-external-links@1?min'
</script>

Use

Say our module example.js looks as follows:

import {unified} from 'unified'
import remarkParse from 'remark-parse'
import remarkRehype from 'remark-rehype'
import rehypeExternalLinks from 'rehype-external-links'
import rehypeStringify from 'rehype-stringify'

main()

async function main() {
  const file = await unified()
    .use(remarkParse)
    .use(remarkRehype)
    .use(rehypeExternalLinks, {target: false, rel: ['nofollow']})
    .use(rehypeStringify)
    .process('[rehype](https://github.com/rehypejs/rehype)')

  console.log(String(file))
}

Now running node example.js yields:

<p><a href="https://github.com/rehypejs/rehype" rel="nofollow">rehype</a></p>

API

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

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

Add rel (and target) to external links.

options

Configuration (optional).

options.target

How to open external documents (string?: _self, _blank, _parent, or _top, default: _blank). Pass false to not set targets on links.

👉 Note: you should likely pass false.

options.rel

Link types to hint about the referenced documents (Array<string> or string, default: ['nofollow', 'noopener', 'noreferrer']). Pass false to not set rels on links.

👉 Note: you should at least set ['nofollow'].

⚠️ Danger: when using a target, add noopener and noreferrer to avoid exploitation of the window.opener API.

options.protocols

Protocols to see as external, such as mailto or tel (Array<string>, default: ['http', 'https']).

options.content

hast content to insert at the end of external links (Node or Children, optional). Will be inserted in a <span> element.

👉 Note: you should set this when using target to adhere to accessibility guidelines by giving users advanced warning when opening a new window.

options.contentProperties

Attributes to add to the <span>s wrapping options.content (Properties, optional).

Types

This package is fully typed with TypeScript. It exports an Options type, which specifies the interface of the accepted options.

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.

This plugin works with rehype-parse version 3+, rehype-stringify version 3+, rehype version 4+, and unified version 6+.

Security

Improper use of rehype-external-links can open you up to a cross-site scripting (XSS) attack.

Either do not combine this plugin with user content or use rehype-sanitize.

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.

License

MIT © Titus Wormer