The AttributesExtension allows HTML attributes to be added from within the document.

Attribute Syntax

The basic syntax was inspired by Kramdown’s Attribute Lists feature.

You can assign any attribute to a block-level element. Just directly prepend or follow the block with a block inline attribute list. That consists of a left curly brace, optionally followed by a colon, the attribute definitions and a right curly brace:

> A nice blockquote
{: title="Blockquote title"}

{#id .class}
## Header

As with a block-level element you can assign any attribute to a span-level elements using a span inline attribute list, that has the same syntax and must immediately follow the span-level element:

This is *red*{style="color: red"}.


This extension is bundled with league/commonmark. This library can be installed via Composer:

composer require league/commonmark

See the installation section for more details.


Configure your Environment as usual and simply add the AttributesExtension:

use League\CommonMark\CommonMarkConverter;
use League\CommonMark\Environment;
use League\CommonMark\Extension\Attributes\AttributesExtension;

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

// Add the extension
$environment->addExtension(new AttributesExtension());

// Set your configuration if needed
$config = [
    // ...

// Instantiate the converter engine and start converting some Markdown!
$converter = new CommonMarkConverter($config, $environment);
echo $converter->convertToHtml('# Hello World!');