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Extension for league/commonmark which adds extra classes and HTML attributes to external links
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Extension to denote external links for league/commonmark

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This extension to the league/commonmark PHP Markdown parser can detect links to external sites and adjust the markup accordingly:

  • Adds a rel="noopener noreferrer" attribute
  • Optionally adds any custom HTML classes


Via Composer

$ composer require league/commonmark-ext-external-link


Configure your Environment as usual and simply add the ExternalLinkExtension provided by this package:

use League\CommonMark\CommonMarkConverter;
use League\CommonMark\Environment;
use League\CommonMark\Ext\ExternalLink\ExternalLinkExtension;

// Obtain a pre-configured Environment with all the CommonMark parsers/renderers ready-to-go
$environment = Environment::createCommonMarkEnvironment();

// Add this extension
$environment->addExtension(new ExternalLinkExtension());

// Set your configuration
$config = [
    'external_link' => [
        'internal_hosts' => '',
        'open_in_new_window' => true,
        'html_class' => 'external-link',

// Instantiate the converter engine and start converting some Markdown!
$converter = new CommonMarkConverter($config, $environment);
echo $converter->convertToHtml('I successfully installed the extension!');


This extension supports three configuration options under the external_link configuration:


This option defines a whitelist of hosts which are considered non-external and should not receive the external link treatment.

This can be a single host name, like '', which must match exactly.

If you need to match subdomains, use a regular expression like '/(^|\.)example\.com$/'. Note that you must use / characters to delimit your regex.

This configuration option also accepts an array of multiple strings and/or regexes:

$config = [
    'external_link' => [
        'internal_hosts' => ['', '', '/(^|\.)google\.com$/],

By default, if this option is not provided, all links will be considered external.


This option (which defaults to false) determines whether any external links should open in a new tab/window.


This option allows you to provide a string containing one or more HTML classes that should be added to the external link <a> tags: No classes are added by default.

Advanced Rendering

When an external link is detected, the ExternalLinkProcessor will set the external data option on the Link node to either true or false. You can therefore create a custom link renderer which checks this value and behaves accordingly:

class MyCustomLinkRenderer implements InlineRendererInterface

     * @param Link                     $inline
     * @param ElementRendererInterface $htmlRenderer
     * @return HtmlElement
    public function render(AbstractInline $inline, ElementRendererInterface $htmlRenderer)
        if (!($inline instanceof Link)) {
            throw new \InvalidArgumentException('Incompatible inline type: ' . \get_class($inline));

        if ($inline->getData('external')) {
            // This is an external link - render it accordingly
        } else {
            // This is an internal link
        // ...


Please see CHANGELOG for more information what has changed recently.


$ composer test


If you discover any security related issues, please email instead of using the issue tracker.



This library is licensed under the BSD-3 license. See the License File for more information.

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