Little bundles of code, little bundles of joy.

Create minimal per-page or app-level bundles of CSS, JavaScript, or HTML to be included in your Eleventy project.

Makes it easy to implement Critical CSS, in-use-only CSS/JS bundles, SVG icon libraries, or secondary HTML content to load via XHR.

This project is a minimum-viable-bundler and asset pipeline in Eleventy. It does not perform any transpilation or code manipulation (by default). The code you put in is the code you get out (with configurable transforms if you’d like to modify the code).

For more larger, more complex use cases you may want to use a more full featured bundler like Vite, Parcel, Webpack, rollup, esbuild, or others.

But do note that a full-featured bundler has a significant build performance cost, so take care to weigh the cost of using that style of bundler against whether or not this plugin has sufficient functionality for your use case—especially as the platform matures and we see diminishing returns on code transpilation (ES modules everywhere).

No installation necessary. Starting with Eleventy v3.0.0-alpha.10 and newer, this plugin is now bundled with Eleventy.

By default, Bundle Plugin v2.0 does not include any default bundles. You must add these yourself via eleventyConfig.addBundle. One notable exception happens when using the WebC Eleventy Plugin, which adds css, js, and html bundles for you.

To create a bundle type, use eleventyConfig.addBundle in your Eleventy configuration file (default .eleventy.js):

// .eleventy.js
module.exports = function(eleventyConfig) {
	eleventyConfig.addBundle("css");
};

This does two things:

1. Creates a new css shortcode for adding arbitrary code to this bundle
2. Adds "css" as an eligible type argument to the getBundle and getBundleFileUrl shortcodes.

module.exports = function(eleventyConfig) {
	eleventyConfig.addBundle("css", {
		// (Optional) Folder (relative to output directory) files will write to
		toFileDirectory: "bundle",

		// (Optional) File extension used for bundle file output, defaults to bundle name
		outputFileExtension: "css",

		// (Optional) Name of shortcode for use in templates, defaults to bundle name
		shortcodeName: "css",
		// shortcodeName: false, // disable this feature.

		// (Optional) Modify bundle content
		transforms: [],

		// (Optional) If two identical code blocks exist in non-default buckets, they’ll be hoisted to the first bucket in common.
		hoist: true,

		// (Optional) In 11ty.js templates, having a named export of `bundle` will populate your bundles.
		bundleExportKey: "bundle",
		// bundleExportKey: false, // disable this feature.
	});
};

Read more about hoist and duplicate bundle hoisting.

The following Universal Shortcodes (available in njk, liquid, hbs, 11ty.js, and webc) are provided by this plugin:

• getBundle to retrieve bundled code as a string.
• getBundleFileUrl to create a bundle file on disk and retrieve the URL to that file.

Here’s a real-world commit showing this in use on the eleventy-base-blog project.

# My Blog Post

This is some content, I am writing markup.

{% css %}
em { font-style: italic; }
{% endcss %}

## More Markdown

{% css %}
strong { font-weight: bold; }
{% endcss %}

Renders to:

<h1>My Blog Post</h1>

<p>This is some content, I am writing markup.</p>

<h2>More Markdown</h2>

Note that the bundled code is excluded!

There are a few more examples below!

<!-- Use this *anywhere*: a layout file, content template, etc -->
<style>{% getBundle "css" %}</style>

<!--
You can add more code to the bundle after calling
getBundle and it will be included.
-->
{% css %}* { color: orange; }{% endcss %}

Writes the bundle content to a content-hashed file location in your output directory and returns the URL to the file for use like this:

<link rel="stylesheet" href="{% getBundleFileUrl "css" %}">

Note that writing bundles to files will likely be slower for empty-cache first time visitors but better cached in the browser for repeat-views (and across multiple pages, too).

<!-- This goes into a `defer` bucket (the bucket can be any string value) -->
{% css "defer" %}em { font-style: italic; }{% endcss %}

<!-- Pass the arbitrary `defer` bucket name as an additional argument -->
<style>{% getBundle "css", "defer" %}</style>
<link rel="stylesheet" href="{% getBundleFileUrl 'css', 'defer' %}">

A default bucket is implied:

<!-- These two statements are the same -->
{% css %}em { font-style: italic; }{% endcss %}
{% css "default" %}em { font-style: italic; }{% endcss %}

<!-- These two are the same too -->
<style>{% getBundle "css" %}</style>
<style>{% getBundle "css", "default" %}</style>

// .eleventy.js
module.exports = function(eleventyConfig) {
	eleventyConfig.addBundle("css");
};

Use asset bucketing to divide CSS between the default bucket and a defer bucket, loaded asynchronously.

(Note that some HTML boilerplate has been omitted from the sample below)

<!-- … -->
<head>
	<!-- Inlined critical styles -->
	<style>{% getBundle "css" %}</style>

	<!-- Deferred non-critical styles -->
	<link rel="stylesheet" href="{% getBundleFileUrl 'css', 'defer' %}" media="print" onload="this.media='all'">
	<noscript>
		<link rel="stylesheet" href="{% getBundleFileUrl 'css', 'defer' %}">
	</noscript>
</head>
<body>
	<!-- This goes into a `default` bucket -->
	{% css %}/* Inline in the head, great with @font-face! */{% endcss %}
	<!-- This goes into a `defer` bucket (the bucket can be any string value) -->
	{% css "defer" %}/* Load me later */{% endcss %}
</body>
<!-- … -->

Related:

• Check out the demo of Critical CSS using Eleventy Edge for a repeat view optimization without JavaScript.
• You may want to improve the above code with fetchpriority when browser support improves.

Here an svg is bundle is created.

// .eleventy.js
module.exports = function(eleventyConfig) {
	eleventyConfig.addBundle("svg");
};

<svg width="0" height="0" aria-hidden="true" style="position: absolute;">
	<defs>{% getBundle "svg" %}</defs>
</svg>

<!-- And anywhere on your page you can add icons to the set -->
{% svg %}
<g id="icon-close"><path d="…" /></g>
{% endsvg %}

And now you can use `icon-close` in as many SVG instances as you’d like (without repeating the heftier SVG content).

<svg><use xlink:href="#icon-close"></use></svg>
<svg><use xlink:href="#icon-close"></use></svg>
<svg><use xlink:href="#icon-close"></use></svg>
<svg><use xlink:href="#icon-close"></use></svg>

// .eleventy.js
module.exports = function(eleventyConfig) {
	eleventyConfig.addBundle("html");
};

This might exist in an Eleventy layout file:

<head>
	{% getBundle "html", "head" %}
</head>

And then in your content you might want to page-specific preconnect:

{% html "head" %}
<link href="https://v1.opengraph.11ty.dev" rel="preconnect" crossorigin>
{% endhtml %}

You can render template syntax inside of the {% css %} shortcode too, if you’d like to do more advanced things using Eleventy template types.

This example assumes you have added the Render plugin and the scss custom template type to your Eleventy configuration file.

{% css %}
  {% renderTemplate "scss" %}
  h1 { .test { color: red; } }
  {% endrenderTemplate %}
{% endcss %}

Now the compiled Sass is available in your default bundle and will show up in getBundle and getBundleFileUrl.

Starting with @11ty/eleventy-plugin-webc@0.9.0 (track at issue #48) this plugin is used by default in the Eleventy WebC plugin. Specifically, WebC Bundler Mode now uses the bundle plugin under the hood.

To add CSS to a bundle in WebC, you would use a <style> element in a WebC page or component:

<style>/* This is bundled. */</style>
<style webc:keep>/* Do not bundle me—leave as is */</style>

To add JS to a page bundle in WebC, you would use a <script> element in a WebC page or component:

<script>/* This is bundled. */</script>
<script webc:keep>/* Do not bundle me—leave as is */</script>

• Existing calls via WebC helpers getCss or getJs (e.g. <style @raw="getCss(page.url)">) have been wired up to getBundle (for "css" and "js" respectively) automatically.
  • For consistency, you may prefer using the bundle plugin method names everywhere: <style @raw="getBundle('css')"> and <script @raw="getBundle('js')"> both work fine.
• Outside of WebC, the Universal Filters webcGetCss and webcGetJs were removed in Eleventy v3.0.0-alpha.10 in favor of the getBundle Universal Shortcode ({% getBundle "css" %} and {% getBundle "js" %} respectively).

You can wire up your own async-friendly callbacks to transform the bundle output too. Here’s a quick example of postcss integration.

const postcss = require("postcss");
const postcssNested = require("postcss-nested");

module.exports = function(eleventyConfig) {
	eleventyConfig.addBundle("css", {
		transforms: [
			async function(content) {
				// this.type returns the bundle name.
				// Same as Eleventy transforms, this.page is available here.
				let result = await postcss([postcssNested]).process(content, { from: this.page.inputPath, to: null });
				return result.css;
			}
		]
	});
};

Bundles do not support nesting or recursion (yet?). If this will be useful to you, please file an issue!